Change Activity Default IdFormat to W3C

src/libraries/System.Private.CoreLib/src/System/LocalAppContextSwitches.Common.cs → src/libraries/Common/src/System/LocalAppContextSwitches.Common.cs

@@ -11,6 +11,11 @@ namespace System
  // every framework assembly that implements any compatibility quirks.
  internal static partial class LocalAppContextSwitches
  {
+ // Returns value of given switch using provided cache.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static bool GetSwitchValue(string switchName, ref bool switchValue) =>
+ AppContext.TryGetSwitch(switchName, out switchValue);
+
  // Returns value of given switch using provided cache.
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
@@ -24,7 +29,6 @@ internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitc
 
  private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  {
-
  bool hasSwitch = AppContext.TryGetSwitch(switchName, out bool isSwitchEnabled);
  if (!hasSwitch)
  {

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -5,7 +5,6 @@
  <NoWarn>$(NoWarn);SA1205</NoWarn>
  <Nullable>enable</Nullable>
  <TargetFrameworks>$(NetCoreAppCurrent);netstandard1.1;netstandard1.3;net45;net46;netstandard2.0;$(NetFrameworkCurrent)</TargetFrameworks>
- <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
  <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
  </PropertyGroup>
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -20,6 +19,7 @@
  <DefineConstants Condition="'$(TargetFramework)' != 'netstandard1.1' and '$(TargetFramework)' != 'netstandard1.3'">$(DefineConstants);EVENTSOURCE_ENUMERATE_SUPPORT</DefineConstants>
  <DefineConstants Condition="$(TargetFramework.StartsWith('net4'))">$(DefineConstants);ALLOW_PARTIALLY_TRUSTED_CALLERS;ENABLE_HTTP_HANDLER</DefineConstants>
  <ExcludeFromPackage Condition="'$(TargetFramework)' == 'netstandard2.0'">true</ExcludeFromPackage>
+ <DefineConstants Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">$(DefineConstants);W3C_DEFAULT_ID_FORMAT</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
  <Compile Include="System\Diagnostics\DiagnosticSource.cs" />
@@ -48,6 +48,12 @@
  <Reference Include="System.Runtime.CompilerServices.Unsafe" />
  <None Include="ActivityUserGuide.md" />
  </ItemGroup>
+ <ItemGroup Condition=" '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+ <Compile Include="System\Diagnostics\LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
+ </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' != 'net45' And '$(TargetFramework)' != 'netstandard1.1'">
  <Compile Include="System\Diagnostics\Activity.Current.net46.cs" />
  </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -51,7 +51,7 @@ public partial class Activity : IDisposable
  private static ActivityIdFormat s_defaultIdFormat;
  /// <summary>
  /// Normally if the ParentID is defined, the format of that is used to determine the
- /// format used by the Activity. However if ForceDefaultFormat is set to true, the
+ /// format used by the Activity. However if ForceDefaultFormat is set to true, the
  /// ID format will always be the DefaultIdFormat even if the ParentID is define and is
  /// a different format.
  /// </summary>
@@ -735,7 +735,13 @@ public static ActivityIdFormat DefaultIdFormat
  get
  {
  if (s_defaultIdFormat == ActivityIdFormat.Unknown)
+ {
+#if W3C_DEFAULT_ID_FORMAT
+ s_defaultIdFormat = LocalAppContextSwitches.DefaultActivityIdFormatIsHierarchial ? ActivityIdFormat.Hierarchical : ActivityIdFormat.W3C;
+#else
  s_defaultIdFormat = ActivityIdFormat.Hierarchical;
+#endif // W3C_DEFAULT_ID_FORMAT
+ }
  return s_defaultIdFormat;
  }
  set

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/LocalAppContextSwitches.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ public static bool DefaultActivityIdFormatIsHierarchial { get; } = InitializeDefaultActivityIdFormat();
+
+ private static bool InitializeDefaultActivityIdFormat()
+ {
+ bool defaultActivityIdFormatIsHierarchial = false;
+
+ if (!LocalAppContextSwitches.GetSwitchValue("System.Diagnostics.DefaultActivityIdFormatIsHierarchial", ref defaultActivityIdFormatIsHierarchial))
+ {
+ string? switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL");
+ if (switchValue != null)
+ {
+ defaultActivityIdFormatIsHierarchial = IsTrueStringIgnoreCase(switchValue) || switchValue.Equals("1");
+ }
+ }
+
+ return defaultActivityIdFormatIsHierarchial;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static bool IsTrueStringIgnoreCase(string value)
+ {
+ return value.Length == 4 &&
+ (value[0] == 't' || value[0] == 'T') &&
+ (value[1] == 'r' || value[1] == 'R') &&
+ (value[2] == 'u' || value[2] == 'U') &&
+ (value[3] == 'e' || value[3] == 'E');
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -188,32 +188,6 @@ public void ActivityIdOverflow()
  Assert.Equal('#', activity.Id[activity.Id.Length - 1]);
  }
 
- /// <summary>
- /// Tests overflow in Id generation when parentId has a single (root) node
- /// </summary>
- [Fact]
- public void ActivityIdNonHierarchicalOverflow()
- {
- // find out Activity Id length on this platform in this AppDomain
- Activity testActivity = new Activity("activity")
- .Start();
- var expectedIdLength = testActivity.Id.Length;
- testActivity.Stop();
-
- // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
- // it causes overflow during Id generation, and new root Id is generated for the new Activity
- var parentId = '|' + new string('a', 1022) + '.';
-
- var activity = new Activity("activity")
- .SetParentId(parentId)
- .Start();
-
- Assert.Equal(parentId, activity.ParentId);
-
- // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
- Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
- Assert.DoesNotContain('#', activity.Id);
- }
 
  /// <summary>
  /// Tests activity start and stop
@@ -258,6 +232,7 @@ public void IdGenerationNoParent()
  public void IdGenerationInternalParent()
  {
  var parent = new Activity("parent");
+ parent.SetIdFormat(ActivityIdFormat.Hierarchical);
  parent.Start();
  var child1 = new Activity("child1");
  var child2 = new Activity("child2");
@@ -535,11 +510,11 @@ public void ActivitySpanIdTests()
  /****** WC3 Format tests *****/
 
  [Fact]
- public void IdFormat_HierarchicalIsDefault()
+ public void IdFormat_W3CIsDefaultForNet5()
  {
  Activity activity = new Activity("activity1");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal(PlatformDetection.IsNetCore ? ActivityIdFormat.W3C : ActivityIdFormat.Hierarchical, activity.IdFormat);
  }
 
  [Fact]
@@ -617,6 +592,20 @@ public void IdFormat_W3CWhenDefaultIsW3C()
  }).Dispose();
  }
 
+ [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ public void IdFormat_WithTheEnvironmentSwitch()
+ {
+ var psi = new ProcessStartInfo();
+ psi.Environment.Add("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL", "true");
+
+ RemoteExecutor.Invoke(() =>
+ {
+ Activity activity = new Activity("activity15");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }, new RemoteInvokeOptions() { StartInfo = psi }).Dispose();
+ }
+
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
  public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  {
@@ -633,13 +622,23 @@ public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  }
 
  [Fact]
- public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ public void IdFormat_ZeroTraceIdAndSpanIdWithW3CFormat()
  {
  Activity activity = new Activity("activity");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
- Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
- Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+
+ if (PlatformDetection.IsNetCore)
+ {
+ Assert.Equal(ActivityIdFormat.W3C, activity.IdFormat);
+ Assert.NotEqual("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.NotEqual("0000000000000000", activity.SpanId.ToHexString());
+ }
+ else
+ {
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
  }
 
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/ActivityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Diagnostics.Tests
+{
+ public class ActivityTests : IDisposable
+ {
+ [Fact]
+ public void ActivityIdNonHierarchicalOverflow()
+ {
+ // find out Activity Id length on this platform in this AppDomain
+ Activity testActivity = new Activity("activity")
+ .Start();
+ var expectedIdLength = testActivity.Id.Length;
+ testActivity.Stop();
+
+ // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
+ // it causes overflow during Id generation, and new root Id is generated for the new Activity
+ var parentId = '|' + new string('a', 1022) + '.';
+
+ var activity = new Activity("activity")
+ .SetParentId(parentId)
+ .Start();
+
+ Assert.Equal(parentId, activity.ParentId);
+
+ // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
+ Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
+ Assert.DoesNotContain('#', activity.Id);
+ }
+
+ [Fact]
+ public void IdGenerationInternalParent()
+ {
+ var parent = new Activity("parent");
+ parent.Start();
+ var child1 = new Activity("child1");
+ var child2 = new Activity("child2");
+ //start 2 children in different execution contexts
+ Task.Run(() => child1.Start()).Wait();
+ Task.Run(() => child2.Start()).Wait();
+
+ // In Debug builds of System.Diagnostics.DiagnosticSource, the child operation Id will be constructed as follows
+ // "|parent.RootId.<child.OperationName.Replace(., -)>-childCount.".
+ // This is for debugging purposes to know which operation the child Id is comming from.
+ //
+ // In Release builds of System.Diagnostics.DiagnosticSource, it will not contain the operation name to keep it simple and it will be as
+ // "|parent.RootId.childCount.".
+
+ string child1DebugString = $"|{parent.RootId}.{child1.OperationName}-1.";
+ string child2DebugString = $"|{parent.RootId}.{child2.OperationName}-2.";
+ string child1ReleaseString = $"|{parent.RootId}.1.";
+ string child2ReleaseString = $"|{parent.RootId}.2.";
+
+ AssertExtensions.AtLeastOneEquals(child1DebugString, child1ReleaseString, child1.Id);
+ AssertExtensions.AtLeastOneEquals(child2DebugString, child2ReleaseString, child2.Id);
+
+ Assert.Equal(parent.RootId, child1.RootId);
+ Assert.Equal(parent.RootId, child2.RootId);
+ child1.Stop();
+ child2.Stop();
+ var child3 = new Activity("child3");
+ child3.Start();
+
+ string child3DebugString = $"|{parent.RootId}.{child3.OperationName}-3.";
+ string child3ReleaseString = $"|{parent.RootId}.3.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, child3.Id);
+
+ var grandChild = new Activity("grandChild");
+ grandChild.Start();
+
+ child3DebugString = $"{child3.Id}{grandChild.OperationName}-1.";
+ child3ReleaseString = $"{child3.Id}1.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, grandChild.Id);
+ }
+
+ [Fact]
+ public void IdFormat_HierarchicalIsDefault()
+ {
+ Activity activity = new Activity("activity1");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }
+
+ [Fact]
+ public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ {
+ Activity activity = new Activity("activity");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
+
+ public void Dispose()
+ {
+ Activity.Current = null;
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/System.Diagnostics.DiagnosticSource.Switches.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+ <TestRuntime>true</TestRuntime>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="ActivityTests.cs" />
+ </ItemGroup>
+</Project>

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+ "configProperties": {
+ "System.Diagnostics.DefaultActivityIdFormatIsHierarchial": true
+ }
+}

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -219,7 +219,7 @@
  <Compile Include="misc\GDI\DeviceContextType.cs" />
  <Compile Include="misc\GDI\WindowsGraphics.cs" />
  <Compile Include="misc\GDI\WindowsRegion.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
  Link="Common\Interop\Windows\Interop.Libraries.cs" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -403,7 +403,6 @@
  <Compile Include="$(MSBuildThisFileDirectory)System\LazyOfTTMetadata.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimization.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimizationAttribute.cs" />
- <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalDataStoreSlot.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\MarshalByRefObject.cs" />
@@ -1083,6 +1082,9 @@
  <Compile Include="$(CommonPath)SkipLocalsInit.cs">
  <Link>Common\SkipLocalsInit.cs</Link>
  </Compile>
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Compile Include="$(CommonPath)System\HResults.cs">
  <Link>Common\System\HResults.cs</Link>
  </Compile>

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -791,7 +791,7 @@
  <Compile Include="System\Xml\Xsl\Xslt\XsltLoader.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XsltQilFactory.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XslVisitor.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="System\Xml\Core\LocalAppContextSwitches.cs" />
  <Compile Include="$(CommonPath)System\CSharpHelpers.cs" />

src/libraries/System.Private.CoreLib/src/System/LocalAppContextSwitches.Common.cs → src/libraries/Common/src/System/LocalAppContextSwitches.Common.cs

@@ -11,6 +11,11 @@ namespace System
  // every framework assembly that implements any compatibility quirks.
  internal static partial class LocalAppContextSwitches
  {
+ // Returns value of given switch using provided cache.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static bool GetSwitchValue(string switchName, ref bool switchValue) =>
+ AppContext.TryGetSwitch(switchName, out switchValue);
+
  // Returns value of given switch using provided cache.
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
@@ -24,7 +29,6 @@ internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitc
 
  private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  {
-
  bool hasSwitch = AppContext.TryGetSwitch(switchName, out bool isSwitchEnabled);
  if (!hasSwitch)
  {

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -5,7 +5,6 @@
  <NoWarn>$(NoWarn);SA1205</NoWarn>
  <Nullable>enable</Nullable>
  <TargetFrameworks>$(NetCoreAppCurrent);netstandard1.1;netstandard1.3;net45;net46;netstandard2.0;$(NetFrameworkCurrent)</TargetFrameworks>
- <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
  <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
  </PropertyGroup>
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -20,6 +19,7 @@
  <DefineConstants Condition="'$(TargetFramework)' != 'netstandard1.1' and '$(TargetFramework)' != 'netstandard1.3'">$(DefineConstants);EVENTSOURCE_ENUMERATE_SUPPORT</DefineConstants>
  <DefineConstants Condition="$(TargetFramework.StartsWith('net4'))">$(DefineConstants);ALLOW_PARTIALLY_TRUSTED_CALLERS;ENABLE_HTTP_HANDLER</DefineConstants>
  <ExcludeFromPackage Condition="'$(TargetFramework)' == 'netstandard2.0'">true</ExcludeFromPackage>
+ <DefineConstants Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">$(DefineConstants);W3C_DEFAULT_ID_FORMAT</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
  <Compile Include="System\Diagnostics\DiagnosticSource.cs" />
@@ -48,6 +48,12 @@
  <Reference Include="System.Runtime.CompilerServices.Unsafe" />
  <None Include="ActivityUserGuide.md" />
  </ItemGroup>
+ <ItemGroup Condition=" '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+ <Compile Include="System\Diagnostics\LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
+ </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' != 'net45' And '$(TargetFramework)' != 'netstandard1.1'">
  <Compile Include="System\Diagnostics\Activity.Current.net46.cs" />
  </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -51,7 +51,7 @@ public partial class Activity : IDisposable
  private static ActivityIdFormat s_defaultIdFormat;
  /// <summary>
  /// Normally if the ParentID is defined, the format of that is used to determine the
- /// format used by the Activity. However if ForceDefaultFormat is set to true, the
+ /// format used by the Activity. However if ForceDefaultFormat is set to true, the
  /// ID format will always be the DefaultIdFormat even if the ParentID is define and is
  /// a different format.
  /// </summary>
@@ -735,7 +735,13 @@ public static ActivityIdFormat DefaultIdFormat
  get
  {
  if (s_defaultIdFormat == ActivityIdFormat.Unknown)
+ {
+#if W3C_DEFAULT_ID_FORMAT
+ s_defaultIdFormat = LocalAppContextSwitches.DefaultActivityIdFormatIsHierarchial ? ActivityIdFormat.Hierarchical : ActivityIdFormat.W3C;
+#else
  s_defaultIdFormat = ActivityIdFormat.Hierarchical;
+#endif // W3C_DEFAULT_ID_FORMAT
+ }
  return s_defaultIdFormat;
  }
  set

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/LocalAppContextSwitches.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ public static bool DefaultActivityIdFormatIsHierarchial { get; } = InitializeDefaultActivityIdFormat();
+
+ private static bool InitializeDefaultActivityIdFormat()
+ {
+ bool defaultActivityIdFormatIsHierarchial = false;
+
+ if (!LocalAppContextSwitches.GetSwitchValue("System.Diagnostics.DefaultActivityIdFormatIsHierarchial", ref defaultActivityIdFormatIsHierarchial))
+ {
+ string? switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL");
+ if (switchValue != null)
+ {
+ defaultActivityIdFormatIsHierarchial = IsTrueStringIgnoreCase(switchValue) || switchValue.Equals("1");
+ }
+ }
+
+ return defaultActivityIdFormatIsHierarchial;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static bool IsTrueStringIgnoreCase(string value)
+ {
+ return value.Length == 4 &&
+ (value[0] == 't' || value[0] == 'T') &&
+ (value[1] == 'r' || value[1] == 'R') &&
+ (value[2] == 'u' || value[2] == 'U') &&
+ (value[3] == 'e' || value[3] == 'E');
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -188,32 +188,6 @@ public void ActivityIdOverflow()
  Assert.Equal('#', activity.Id[activity.Id.Length - 1]);
  }
 
- /// <summary>
- /// Tests overflow in Id generation when parentId has a single (root) node
- /// </summary>
- [Fact]
- public void ActivityIdNonHierarchicalOverflow()
- {
- // find out Activity Id length on this platform in this AppDomain
- Activity testActivity = new Activity("activity")
- .Start();
- var expectedIdLength = testActivity.Id.Length;
- testActivity.Stop();
-
- // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
- // it causes overflow during Id generation, and new root Id is generated for the new Activity
- var parentId = '|' + new string('a', 1022) + '.';
-
- var activity = new Activity("activity")
- .SetParentId(parentId)
- .Start();
-
- Assert.Equal(parentId, activity.ParentId);
-
- // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
- Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
- Assert.DoesNotContain('#', activity.Id);
- }
 
  /// <summary>
  /// Tests activity start and stop
@@ -258,6 +232,7 @@ public void IdGenerationNoParent()
  public void IdGenerationInternalParent()
  {
  var parent = new Activity("parent");
+ parent.SetIdFormat(ActivityIdFormat.Hierarchical);
  parent.Start();
  var child1 = new Activity("child1");
  var child2 = new Activity("child2");
@@ -535,11 +510,11 @@ public void ActivitySpanIdTests()
  /****** WC3 Format tests *****/
 
  [Fact]
- public void IdFormat_HierarchicalIsDefault()
+ public void IdFormat_W3CIsDefaultForNet5()
  {
  Activity activity = new Activity("activity1");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal(PlatformDetection.IsNetCore ? ActivityIdFormat.W3C : ActivityIdFormat.Hierarchical, activity.IdFormat);
  }
 
  [Fact]
@@ -617,6 +592,20 @@ public void IdFormat_W3CWhenDefaultIsW3C()
  }).Dispose();
  }
 
+ [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ public void IdFormat_WithTheEnvironmentSwitch()
+ {
+ var psi = new ProcessStartInfo();
+ psi.Environment.Add("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL", "true");
+
+ RemoteExecutor.Invoke(() =>
+ {
+ Activity activity = new Activity("activity15");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }, new RemoteInvokeOptions() { StartInfo = psi }).Dispose();
+ }
+
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
  public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  {
@@ -633,13 +622,23 @@ public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  }
 
  [Fact]
- public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ public void IdFormat_ZeroTraceIdAndSpanIdWithW3CFormat()
  {
  Activity activity = new Activity("activity");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
- Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
- Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+
+ if (PlatformDetection.IsNetCore)
+ {
+ Assert.Equal(ActivityIdFormat.W3C, activity.IdFormat);
+ Assert.NotEqual("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.NotEqual("0000000000000000", activity.SpanId.ToHexString());
+ }
+ else
+ {
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
  }
 
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/ActivityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Diagnostics.Tests
+{
+ public class ActivityTests : IDisposable
+ {
+ [Fact]
+ public void ActivityIdNonHierarchicalOverflow()
+ {
+ // find out Activity Id length on this platform in this AppDomain
+ Activity testActivity = new Activity("activity")
+ .Start();
+ var expectedIdLength = testActivity.Id.Length;
+ testActivity.Stop();
+
+ // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
+ // it causes overflow during Id generation, and new root Id is generated for the new Activity
+ var parentId = '|' + new string('a', 1022) + '.';
+
+ var activity = new Activity("activity")
+ .SetParentId(parentId)
+ .Start();
+
+ Assert.Equal(parentId, activity.ParentId);
+
+ // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
+ Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
+ Assert.DoesNotContain('#', activity.Id);
+ }
+
+ [Fact]
+ public void IdGenerationInternalParent()
+ {
+ var parent = new Activity("parent");
+ parent.Start();
+ var child1 = new Activity("child1");
+ var child2 = new Activity("child2");
+ //start 2 children in different execution contexts
+ Task.Run(() => child1.Start()).Wait();
+ Task.Run(() => child2.Start()).Wait();
+
+ // In Debug builds of System.Diagnostics.DiagnosticSource, the child operation Id will be constructed as follows
+ // "|parent.RootId.<child.OperationName.Replace(., -)>-childCount.".
+ // This is for debugging purposes to know which operation the child Id is comming from.
+ //
+ // In Release builds of System.Diagnostics.DiagnosticSource, it will not contain the operation name to keep it simple and it will be as
+ // "|parent.RootId.childCount.".
+
+ string child1DebugString = $"|{parent.RootId}.{child1.OperationName}-1.";
+ string child2DebugString = $"|{parent.RootId}.{child2.OperationName}-2.";
+ string child1ReleaseString = $"|{parent.RootId}.1.";
+ string child2ReleaseString = $"|{parent.RootId}.2.";
+
+ AssertExtensions.AtLeastOneEquals(child1DebugString, child1ReleaseString, child1.Id);
+ AssertExtensions.AtLeastOneEquals(child2DebugString, child2ReleaseString, child2.Id);
+
+ Assert.Equal(parent.RootId, child1.RootId);
+ Assert.Equal(parent.RootId, child2.RootId);
+ child1.Stop();
+ child2.Stop();
+ var child3 = new Activity("child3");
+ child3.Start();
+
+ string child3DebugString = $"|{parent.RootId}.{child3.OperationName}-3.";
+ string child3ReleaseString = $"|{parent.RootId}.3.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, child3.Id);
+
+ var grandChild = new Activity("grandChild");
+ grandChild.Start();
+
+ child3DebugString = $"{child3.Id}{grandChild.OperationName}-1.";
+ child3ReleaseString = $"{child3.Id}1.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, grandChild.Id);
+ }
+
+ [Fact]
+ public void IdFormat_HierarchicalIsDefault()
+ {
+ Activity activity = new Activity("activity1");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }
+
+ [Fact]
+ public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ {
+ Activity activity = new Activity("activity");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
+
+ public void Dispose()
+ {
+ Activity.Current = null;
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/System.Diagnostics.DiagnosticSource.Switches.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+ <TestRuntime>true</TestRuntime>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="ActivityTests.cs" />
+ </ItemGroup>
+</Project>

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+ "configProperties": {
+ "System.Diagnostics.DefaultActivityIdFormatIsHierarchial": true
+ }
+}

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -219,7 +219,7 @@
  <Compile Include="misc\GDI\DeviceContextType.cs" />
  <Compile Include="misc\GDI\WindowsGraphics.cs" />
  <Compile Include="misc\GDI\WindowsRegion.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
  Link="Common\Interop\Windows\Interop.Libraries.cs" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -403,7 +403,6 @@
  <Compile Include="$(MSBuildThisFileDirectory)System\LazyOfTTMetadata.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimization.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimizationAttribute.cs" />
- <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalDataStoreSlot.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\MarshalByRefObject.cs" />
@@ -1083,6 +1082,9 @@
  <Compile Include="$(CommonPath)SkipLocalsInit.cs">
  <Link>Common\SkipLocalsInit.cs</Link>
  </Compile>
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Compile Include="$(CommonPath)System\HResults.cs">
  <Link>Common\System\HResults.cs</Link>
  </Compile>

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -791,7 +791,7 @@
  <Compile Include="System\Xml\Xsl\Xslt\XsltLoader.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XsltQilFactory.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XslVisitor.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="System\Xml\Core\LocalAppContextSwitches.cs" />
  <Compile Include="$(CommonPath)System\CSharpHelpers.cs" />

src/libraries/System.Private.CoreLib/src/System/LocalAppContextSwitches.Common.cs → src/libraries/Common/src/System/LocalAppContextSwitches.Common.cs

@@ -11,6 +11,11 @@ namespace System
  // every framework assembly that implements any compatibility quirks.
  internal static partial class LocalAppContextSwitches
  {
+ // Returns value of given switch using provided cache.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static bool GetSwitchValue(string switchName, ref bool switchValue) =>
+ AppContext.TryGetSwitch(switchName, out switchValue);
+
  // Returns value of given switch using provided cache.
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
@@ -24,7 +29,6 @@ internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitc
 
  private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  {
-
  bool hasSwitch = AppContext.TryGetSwitch(switchName, out bool isSwitchEnabled);
  if (!hasSwitch)
  {

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -5,7 +5,6 @@
  <NoWarn>$(NoWarn);SA1205</NoWarn>
  <Nullable>enable</Nullable>
  <TargetFrameworks>$(NetCoreAppCurrent);netstandard1.1;netstandard1.3;net45;net46;netstandard2.0;$(NetFrameworkCurrent)</TargetFrameworks>
- <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
  <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
  </PropertyGroup>
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -20,6 +19,7 @@
  <DefineConstants Condition="'$(TargetFramework)' != 'netstandard1.1' and '$(TargetFramework)' != 'netstandard1.3'">$(DefineConstants);EVENTSOURCE_ENUMERATE_SUPPORT</DefineConstants>
  <DefineConstants Condition="$(TargetFramework.StartsWith('net4'))">$(DefineConstants);ALLOW_PARTIALLY_TRUSTED_CALLERS;ENABLE_HTTP_HANDLER</DefineConstants>
  <ExcludeFromPackage Condition="'$(TargetFramework)' == 'netstandard2.0'">true</ExcludeFromPackage>
+ <DefineConstants Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">$(DefineConstants);W3C_DEFAULT_ID_FORMAT</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
  <Compile Include="System\Diagnostics\DiagnosticSource.cs" />
@@ -48,6 +48,12 @@
  <Reference Include="System.Runtime.CompilerServices.Unsafe" />
  <None Include="ActivityUserGuide.md" />
  </ItemGroup>
+ <ItemGroup Condition=" '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+ <Compile Include="System\Diagnostics\LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
+ </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' != 'net45' And '$(TargetFramework)' != 'netstandard1.1'">
  <Compile Include="System\Diagnostics\Activity.Current.net46.cs" />
  </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -51,7 +51,7 @@ public partial class Activity : IDisposable
  private static ActivityIdFormat s_defaultIdFormat;
  /// <summary>
  /// Normally if the ParentID is defined, the format of that is used to determine the
- /// format used by the Activity. However if ForceDefaultFormat is set to true, the
+ /// format used by the Activity. However if ForceDefaultFormat is set to true, the
  /// ID format will always be the DefaultIdFormat even if the ParentID is define and is
  /// a different format.
  /// </summary>
@@ -735,7 +735,13 @@ public static ActivityIdFormat DefaultIdFormat
  get
  {
  if (s_defaultIdFormat == ActivityIdFormat.Unknown)
+ {
+#if W3C_DEFAULT_ID_FORMAT
+ s_defaultIdFormat = LocalAppContextSwitches.DefaultActivityIdFormatIsHierarchial ? ActivityIdFormat.Hierarchical : ActivityIdFormat.W3C;
+#else
  s_defaultIdFormat = ActivityIdFormat.Hierarchical;
+#endif // W3C_DEFAULT_ID_FORMAT
+ }
  return s_defaultIdFormat;
  }
  set

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/LocalAppContextSwitches.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ public static bool DefaultActivityIdFormatIsHierarchial { get; } = InitializeDefaultActivityIdFormat();
+
+ private static bool InitializeDefaultActivityIdFormat()
+ {
+ bool defaultActivityIdFormatIsHierarchial = false;
+
+ if (!LocalAppContextSwitches.GetSwitchValue("System.Diagnostics.DefaultActivityIdFormatIsHierarchial", ref defaultActivityIdFormatIsHierarchial))
+ {
+ string? switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL");
+ if (switchValue != null)
+ {
+ defaultActivityIdFormatIsHierarchial = IsTrueStringIgnoreCase(switchValue) || switchValue.Equals("1");
+ }
+ }
+
+ return defaultActivityIdFormatIsHierarchial;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static bool IsTrueStringIgnoreCase(string value)
+ {
+ return value.Length == 4 &&
+ (value[0] == 't' || value[0] == 'T') &&
+ (value[1] == 'r' || value[1] == 'R') &&
+ (value[2] == 'u' || value[2] == 'U') &&
+ (value[3] == 'e' || value[3] == 'E');
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -188,32 +188,6 @@ public void ActivityIdOverflow()
  Assert.Equal('#', activity.Id[activity.Id.Length - 1]);
  }
 
- /// <summary>
- /// Tests overflow in Id generation when parentId has a single (root) node
- /// </summary>
- [Fact]
- public void ActivityIdNonHierarchicalOverflow()
- {
- // find out Activity Id length on this platform in this AppDomain
- Activity testActivity = new Activity("activity")
- .Start();
- var expectedIdLength = testActivity.Id.Length;
- testActivity.Stop();
-
- // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
- // it causes overflow during Id generation, and new root Id is generated for the new Activity
- var parentId = '|' + new string('a', 1022) + '.';
-
- var activity = new Activity("activity")
- .SetParentId(parentId)
- .Start();
-
- Assert.Equal(parentId, activity.ParentId);
-
- // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
- Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
- Assert.DoesNotContain('#', activity.Id);
- }
 
  /// <summary>
  /// Tests activity start and stop
@@ -258,6 +232,7 @@ public void IdGenerationNoParent()
  public void IdGenerationInternalParent()
  {
  var parent = new Activity("parent");
+ parent.SetIdFormat(ActivityIdFormat.Hierarchical);
  parent.Start();
  var child1 = new Activity("child1");
  var child2 = new Activity("child2");
@@ -535,11 +510,11 @@ public void ActivitySpanIdTests()
  /****** WC3 Format tests *****/
 
  [Fact]
- public void IdFormat_HierarchicalIsDefault()
+ public void IdFormat_W3CIsDefaultForNet5()
  {
  Activity activity = new Activity("activity1");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal(PlatformDetection.IsNetCore ? ActivityIdFormat.W3C : ActivityIdFormat.Hierarchical, activity.IdFormat);
  }
 
  [Fact]
@@ -617,6 +592,20 @@ public void IdFormat_W3CWhenDefaultIsW3C()
  }).Dispose();
  }
 
+ [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ public void IdFormat_WithTheEnvironmentSwitch()
+ {
+ var psi = new ProcessStartInfo();
+ psi.Environment.Add("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL", "true");
+
+ RemoteExecutor.Invoke(() =>
+ {
+ Activity activity = new Activity("activity15");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }, new RemoteInvokeOptions() { StartInfo = psi }).Dispose();
+ }
+
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
  public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  {
@@ -633,13 +622,23 @@ public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  }
 
  [Fact]
- public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ public void IdFormat_ZeroTraceIdAndSpanIdWithW3CFormat()
  {
  Activity activity = new Activity("activity");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
- Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
- Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+
+ if (PlatformDetection.IsNetCore)
+ {
+ Assert.Equal(ActivityIdFormat.W3C, activity.IdFormat);
+ Assert.NotEqual("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.NotEqual("0000000000000000", activity.SpanId.ToHexString());
+ }
+ else
+ {
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
  }
 
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/ActivityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Diagnostics.Tests
+{
+ public class ActivityTests : IDisposable
+ {
+ [Fact]
+ public void ActivityIdNonHierarchicalOverflow()
+ {
+ // find out Activity Id length on this platform in this AppDomain
+ Activity testActivity = new Activity("activity")
+ .Start();
+ var expectedIdLength = testActivity.Id.Length;
+ testActivity.Stop();
+
+ // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
+ // it causes overflow during Id generation, and new root Id is generated for the new Activity
+ var parentId = '|' + new string('a', 1022) + '.';
+
+ var activity = new Activity("activity")
+ .SetParentId(parentId)
+ .Start();
+
+ Assert.Equal(parentId, activity.ParentId);
+
+ // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
+ Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
+ Assert.DoesNotContain('#', activity.Id);
+ }
+
+ [Fact]
+ public void IdGenerationInternalParent()
+ {
+ var parent = new Activity("parent");
+ parent.Start();
+ var child1 = new Activity("child1");
+ var child2 = new Activity("child2");
+ //start 2 children in different execution contexts
+ Task.Run(() => child1.Start()).Wait();
+ Task.Run(() => child2.Start()).Wait();
+
+ // In Debug builds of System.Diagnostics.DiagnosticSource, the child operation Id will be constructed as follows
+ // "|parent.RootId.<child.OperationName.Replace(., -)>-childCount.".
+ // This is for debugging purposes to know which operation the child Id is comming from.
+ //
+ // In Release builds of System.Diagnostics.DiagnosticSource, it will not contain the operation name to keep it simple and it will be as
+ // "|parent.RootId.childCount.".
+
+ string child1DebugString = $"|{parent.RootId}.{child1.OperationName}-1.";
+ string child2DebugString = $"|{parent.RootId}.{child2.OperationName}-2.";
+ string child1ReleaseString = $"|{parent.RootId}.1.";
+ string child2ReleaseString = $"|{parent.RootId}.2.";
+
+ AssertExtensions.AtLeastOneEquals(child1DebugString, child1ReleaseString, child1.Id);
+ AssertExtensions.AtLeastOneEquals(child2DebugString, child2ReleaseString, child2.Id);
+
+ Assert.Equal(parent.RootId, child1.RootId);
+ Assert.Equal(parent.RootId, child2.RootId);
+ child1.Stop();
+ child2.Stop();
+ var child3 = new Activity("child3");
+ child3.Start();
+
+ string child3DebugString = $"|{parent.RootId}.{child3.OperationName}-3.";
+ string child3ReleaseString = $"|{parent.RootId}.3.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, child3.Id);
+
+ var grandChild = new Activity("grandChild");
+ grandChild.Start();
+
+ child3DebugString = $"{child3.Id}{grandChild.OperationName}-1.";
+ child3ReleaseString = $"{child3.Id}1.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, grandChild.Id);
+ }
+
+ [Fact]
+ public void IdFormat_HierarchicalIsDefault()
+ {
+ Activity activity = new Activity("activity1");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }
+
+ [Fact]
+ public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ {
+ Activity activity = new Activity("activity");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
+
+ public void Dispose()
+ {
+ Activity.Current = null;
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/System.Diagnostics.DiagnosticSource.Switches.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+ <TestRuntime>true</TestRuntime>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="ActivityTests.cs" />
+ </ItemGroup>
+</Project>

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+ "configProperties": {
+ "System.Diagnostics.DefaultActivityIdFormatIsHierarchial": true
+ }
+}

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -219,7 +219,7 @@
  <Compile Include="misc\GDI\DeviceContextType.cs" />
  <Compile Include="misc\GDI\WindowsGraphics.cs" />
  <Compile Include="misc\GDI\WindowsRegion.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
  Link="Common\Interop\Windows\Interop.Libraries.cs" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -403,7 +403,6 @@
  <Compile Include="$(MSBuildThisFileDirectory)System\LazyOfTTMetadata.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimization.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimizationAttribute.cs" />
- <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalDataStoreSlot.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\MarshalByRefObject.cs" />
@@ -1083,6 +1082,9 @@
  <Compile Include="$(CommonPath)SkipLocalsInit.cs">
  <Link>Common\SkipLocalsInit.cs</Link>
  </Compile>
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Compile Include="$(CommonPath)System\HResults.cs">
  <Link>Common\System\HResults.cs</Link>
  </Compile>

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -791,7 +791,7 @@
  <Compile Include="System\Xml\Xsl\Xslt\XsltLoader.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XsltQilFactory.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XslVisitor.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="System\Xml\Core\LocalAppContextSwitches.cs" />
  <Compile Include="$(CommonPath)System\CSharpHelpers.cs" />

src/libraries/System.Private.CoreLib/src/System/LocalAppContextSwitches.Common.cs → src/libraries/Common/src/System/LocalAppContextSwitches.Common.cs

@@ -11,6 +11,11 @@ namespace System
  // every framework assembly that implements any compatibility quirks.
  internal static partial class LocalAppContextSwitches
  {
+ // Returns value of given switch using provided cache.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static bool GetSwitchValue(string switchName, ref bool switchValue) =>
+ AppContext.TryGetSwitch(switchName, out switchValue);
+
  // Returns value of given switch using provided cache.
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
@@ -24,7 +29,6 @@ internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitc
 
  private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  {
-
  bool hasSwitch = AppContext.TryGetSwitch(switchName, out bool isSwitchEnabled);
  if (!hasSwitch)
  {

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -5,7 +5,6 @@
  <NoWarn>$(NoWarn);SA1205</NoWarn>
  <Nullable>enable</Nullable>
  <TargetFrameworks>$(NetCoreAppCurrent);netstandard1.1;netstandard1.3;net45;net46;netstandard2.0;$(NetFrameworkCurrent)</TargetFrameworks>
- <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
  <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
  </PropertyGroup>
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -20,6 +19,7 @@
  <DefineConstants Condition="'$(TargetFramework)' != 'netstandard1.1' and '$(TargetFramework)' != 'netstandard1.3'">$(DefineConstants);EVENTSOURCE_ENUMERATE_SUPPORT</DefineConstants>
  <DefineConstants Condition="$(TargetFramework.StartsWith('net4'))">$(DefineConstants);ALLOW_PARTIALLY_TRUSTED_CALLERS;ENABLE_HTTP_HANDLER</DefineConstants>
  <ExcludeFromPackage Condition="'$(TargetFramework)' == 'netstandard2.0'">true</ExcludeFromPackage>
+ <DefineConstants Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">$(DefineConstants);W3C_DEFAULT_ID_FORMAT</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
  <Compile Include="System\Diagnostics\DiagnosticSource.cs" />
@@ -48,6 +48,12 @@
  <Reference Include="System.Runtime.CompilerServices.Unsafe" />
  <None Include="ActivityUserGuide.md" />
  </ItemGroup>
+ <ItemGroup Condition=" '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+ <Compile Include="System\Diagnostics\LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
+ </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' != 'net45' And '$(TargetFramework)' != 'netstandard1.1'">
  <Compile Include="System\Diagnostics\Activity.Current.net46.cs" />
  </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -51,7 +51,7 @@ public partial class Activity : IDisposable
  private static ActivityIdFormat s_defaultIdFormat;
  /// <summary>
  /// Normally if the ParentID is defined, the format of that is used to determine the
- /// format used by the Activity. However if ForceDefaultFormat is set to true, the
+ /// format used by the Activity. However if ForceDefaultFormat is set to true, the
  /// ID format will always be the DefaultIdFormat even if the ParentID is define and is
  /// a different format.
  /// </summary>
@@ -735,7 +735,13 @@ public static ActivityIdFormat DefaultIdFormat
  get
  {
  if (s_defaultIdFormat == ActivityIdFormat.Unknown)
+ {
+#if W3C_DEFAULT_ID_FORMAT
+ s_defaultIdFormat = LocalAppContextSwitches.DefaultActivityIdFormatIsHierarchial ? ActivityIdFormat.Hierarchical : ActivityIdFormat.W3C;
+#else
  s_defaultIdFormat = ActivityIdFormat.Hierarchical;
+#endif // W3C_DEFAULT_ID_FORMAT
+ }
  return s_defaultIdFormat;
  }
  set

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/LocalAppContextSwitches.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ public static bool DefaultActivityIdFormatIsHierarchial { get; } = InitializeDefaultActivityIdFormat();
+
+ private static bool InitializeDefaultActivityIdFormat()
+ {
+ bool defaultActivityIdFormatIsHierarchial = false;
+
+ if (!LocalAppContextSwitches.GetSwitchValue("System.Diagnostics.DefaultActivityIdFormatIsHierarchial", ref defaultActivityIdFormatIsHierarchial))
+ {
+ string? switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL");
+ if (switchValue != null)
+ {
+ defaultActivityIdFormatIsHierarchial = IsTrueStringIgnoreCase(switchValue) || switchValue.Equals("1");
+ }
+ }
+
+ return defaultActivityIdFormatIsHierarchial;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static bool IsTrueStringIgnoreCase(string value)
+ {
+ return value.Length == 4 &&
+ (value[0] == 't' || value[0] == 'T') &&
+ (value[1] == 'r' || value[1] == 'R') &&
+ (value[2] == 'u' || value[2] == 'U') &&
+ (value[3] == 'e' || value[3] == 'E');
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -188,32 +188,6 @@ public void ActivityIdOverflow()
  Assert.Equal('#', activity.Id[activity.Id.Length - 1]);
  }
 
- /// <summary>
- /// Tests overflow in Id generation when parentId has a single (root) node
- /// </summary>
- [Fact]
- public void ActivityIdNonHierarchicalOverflow()
- {
- // find out Activity Id length on this platform in this AppDomain
- Activity testActivity = new Activity("activity")
- .Start();
- var expectedIdLength = testActivity.Id.Length;
- testActivity.Stop();
-
- // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
- // it causes overflow during Id generation, and new root Id is generated for the new Activity
- var parentId = '|' + new string('a', 1022) + '.';
-
- var activity = new Activity("activity")
- .SetParentId(parentId)
- .Start();
-
- Assert.Equal(parentId, activity.ParentId);
-
- // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
- Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
- Assert.DoesNotContain('#', activity.Id);
- }
 
  /// <summary>
  /// Tests activity start and stop
@@ -258,6 +232,7 @@ public void IdGenerationNoParent()
  public void IdGenerationInternalParent()
  {
  var parent = new Activity("parent");
+ parent.SetIdFormat(ActivityIdFormat.Hierarchical);
  parent.Start();
  var child1 = new Activity("child1");
  var child2 = new Activity("child2");
@@ -535,11 +510,11 @@ public void ActivitySpanIdTests()
  /****** WC3 Format tests *****/
 
  [Fact]
- public void IdFormat_HierarchicalIsDefault()
+ public void IdFormat_W3CIsDefaultForNet5()
  {
  Activity activity = new Activity("activity1");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal(PlatformDetection.IsNetCore ? ActivityIdFormat.W3C : ActivityIdFormat.Hierarchical, activity.IdFormat);
  }
 
  [Fact]
@@ -617,6 +592,20 @@ public void IdFormat_W3CWhenDefaultIsW3C()
  }).Dispose();
  }
 
+ [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ public void IdFormat_WithTheEnvironmentSwitch()
+ {
+ var psi = new ProcessStartInfo();
+ psi.Environment.Add("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL", "true");
+
+ RemoteExecutor.Invoke(() =>
+ {
+ Activity activity = new Activity("activity15");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }, new RemoteInvokeOptions() { StartInfo = psi }).Dispose();
+ }
+
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
  public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  {
@@ -633,13 +622,23 @@ public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  }
 
  [Fact]
- public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ public void IdFormat_ZeroTraceIdAndSpanIdWithW3CFormat()
  {
  Activity activity = new Activity("activity");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
- Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
- Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+
+ if (PlatformDetection.IsNetCore)
+ {
+ Assert.Equal(ActivityIdFormat.W3C, activity.IdFormat);
+ Assert.NotEqual("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.NotEqual("0000000000000000", activity.SpanId.ToHexString());
+ }
+ else
+ {
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
  }
 
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/ActivityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Diagnostics.Tests
+{
+ public class ActivityTests : IDisposable
+ {
+ [Fact]
+ public void ActivityIdNonHierarchicalOverflow()
+ {
+ // find out Activity Id length on this platform in this AppDomain
+ Activity testActivity = new Activity("activity")
+ .Start();
+ var expectedIdLength = testActivity.Id.Length;
+ testActivity.Stop();
+
+ // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
+ // it causes overflow during Id generation, and new root Id is generated for the new Activity
+ var parentId = '|' + new string('a', 1022) + '.';
+
+ var activity = new Activity("activity")
+ .SetParentId(parentId)
+ .Start();
+
+ Assert.Equal(parentId, activity.ParentId);
+
+ // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
+ Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
+ Assert.DoesNotContain('#', activity.Id);
+ }
+
+ [Fact]
+ public void IdGenerationInternalParent()
+ {
+ var parent = new Activity("parent");
+ parent.Start();
+ var child1 = new Activity("child1");
+ var child2 = new Activity("child2");
+ //start 2 children in different execution contexts
+ Task.Run(() => child1.Start()).Wait();
+ Task.Run(() => child2.Start()).Wait();
+
+ // In Debug builds of System.Diagnostics.DiagnosticSource, the child operation Id will be constructed as follows
+ // "|parent.RootId.<child.OperationName.Replace(., -)>-childCount.".
+ // This is for debugging purposes to know which operation the child Id is comming from.
+ //
+ // In Release builds of System.Diagnostics.DiagnosticSource, it will not contain the operation name to keep it simple and it will be as
+ // "|parent.RootId.childCount.".
+
+ string child1DebugString = $"|{parent.RootId}.{child1.OperationName}-1.";
+ string child2DebugString = $"|{parent.RootId}.{child2.OperationName}-2.";
+ string child1ReleaseString = $"|{parent.RootId}.1.";
+ string child2ReleaseString = $"|{parent.RootId}.2.";
+
+ AssertExtensions.AtLeastOneEquals(child1DebugString, child1ReleaseString, child1.Id);
+ AssertExtensions.AtLeastOneEquals(child2DebugString, child2ReleaseString, child2.Id);
+
+ Assert.Equal(parent.RootId, child1.RootId);
+ Assert.Equal(parent.RootId, child2.RootId);
+ child1.Stop();
+ child2.Stop();
+ var child3 = new Activity("child3");
+ child3.Start();
+
+ string child3DebugString = $"|{parent.RootId}.{child3.OperationName}-3.";
+ string child3ReleaseString = $"|{parent.RootId}.3.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, child3.Id);
+
+ var grandChild = new Activity("grandChild");
+ grandChild.Start();
+
+ child3DebugString = $"{child3.Id}{grandChild.OperationName}-1.";
+ child3ReleaseString = $"{child3.Id}1.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, grandChild.Id);
+ }
+
+ [Fact]
+ public void IdFormat_HierarchicalIsDefault()
+ {
+ Activity activity = new Activity("activity1");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }
+
+ [Fact]
+ public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ {
+ Activity activity = new Activity("activity");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
+
+ public void Dispose()
+ {
+ Activity.Current = null;
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/System.Diagnostics.DiagnosticSource.Switches.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+ <TestRuntime>true</TestRuntime>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="ActivityTests.cs" />
+ </ItemGroup>
+</Project>

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+ "configProperties": {
+ "System.Diagnostics.DefaultActivityIdFormatIsHierarchial": true
+ }
+}

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -219,7 +219,7 @@
  <Compile Include="misc\GDI\DeviceContextType.cs" />
  <Compile Include="misc\GDI\WindowsGraphics.cs" />
  <Compile Include="misc\GDI\WindowsRegion.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
  Link="Common\Interop\Windows\Interop.Libraries.cs" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -403,7 +403,6 @@
  <Compile Include="$(MSBuildThisFileDirectory)System\LazyOfTTMetadata.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimization.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimizationAttribute.cs" />
- <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalDataStoreSlot.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\MarshalByRefObject.cs" />
@@ -1083,6 +1082,9 @@
  <Compile Include="$(CommonPath)SkipLocalsInit.cs">
  <Link>Common\SkipLocalsInit.cs</Link>
  </Compile>
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Compile Include="$(CommonPath)System\HResults.cs">
  <Link>Common\System\HResults.cs</Link>
  </Compile>

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -791,7 +791,7 @@
  <Compile Include="System\Xml\Xsl\Xslt\XsltLoader.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XsltQilFactory.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XslVisitor.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="System\Xml\Core\LocalAppContextSwitches.cs" />
  <Compile Include="$(CommonPath)System\CSharpHelpers.cs" />

src/libraries/System.Private.CoreLib/src/System/LocalAppContextSwitches.Common.cs → src/libraries/Common/src/System/LocalAppContextSwitches.Common.cs

@@ -11,6 +11,11 @@ namespace System
  // every framework assembly that implements any compatibility quirks.
  internal static partial class LocalAppContextSwitches
  {
+ // Returns value of given switch using provided cache.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static bool GetSwitchValue(string switchName, ref bool switchValue) =>
+ AppContext.TryGetSwitch(switchName, out switchValue);
+
  // Returns value of given switch using provided cache.
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
@@ -24,7 +29,6 @@ internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitc
 
  private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  {
-
  bool hasSwitch = AppContext.TryGetSwitch(switchName, out bool isSwitchEnabled);
  if (!hasSwitch)
  {

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -5,7 +5,6 @@
  <NoWarn>$(NoWarn);SA1205</NoWarn>
  <Nullable>enable</Nullable>
  <TargetFrameworks>$(NetCoreAppCurrent);netstandard1.1;netstandard1.3;net45;net46;netstandard2.0;$(NetFrameworkCurrent)</TargetFrameworks>
- <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
  <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
  </PropertyGroup>
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -20,6 +19,7 @@
  <DefineConstants Condition="'$(TargetFramework)' != 'netstandard1.1' and '$(TargetFramework)' != 'netstandard1.3'">$(DefineConstants);EVENTSOURCE_ENUMERATE_SUPPORT</DefineConstants>
  <DefineConstants Condition="$(TargetFramework.StartsWith('net4'))">$(DefineConstants);ALLOW_PARTIALLY_TRUSTED_CALLERS;ENABLE_HTTP_HANDLER</DefineConstants>
  <ExcludeFromPackage Condition="'$(TargetFramework)' == 'netstandard2.0'">true</ExcludeFromPackage>
+ <DefineConstants Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">$(DefineConstants);W3C_DEFAULT_ID_FORMAT</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
  <Compile Include="System\Diagnostics\DiagnosticSource.cs" />
@@ -48,6 +48,12 @@
  <Reference Include="System.Runtime.CompilerServices.Unsafe" />
  <None Include="ActivityUserGuide.md" />
  </ItemGroup>
+ <ItemGroup Condition=" '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+ <Compile Include="System\Diagnostics\LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
+ </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' != 'net45' And '$(TargetFramework)' != 'netstandard1.1'">
  <Compile Include="System\Diagnostics\Activity.Current.net46.cs" />
  </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -51,7 +51,7 @@ public partial class Activity : IDisposable
  private static ActivityIdFormat s_defaultIdFormat;
  /// <summary>
  /// Normally if the ParentID is defined, the format of that is used to determine the
- /// format used by the Activity. However if ForceDefaultFormat is set to true, the
+ /// format used by the Activity. However if ForceDefaultFormat is set to true, the
  /// ID format will always be the DefaultIdFormat even if the ParentID is define and is
  /// a different format.
  /// </summary>
@@ -735,7 +735,13 @@ public static ActivityIdFormat DefaultIdFormat
  get
  {
  if (s_defaultIdFormat == ActivityIdFormat.Unknown)
+ {
+#if W3C_DEFAULT_ID_FORMAT
+ s_defaultIdFormat = LocalAppContextSwitches.DefaultActivityIdFormatIsHierarchial ? ActivityIdFormat.Hierarchical : ActivityIdFormat.W3C;
+#else
  s_defaultIdFormat = ActivityIdFormat.Hierarchical;
+#endif // W3C_DEFAULT_ID_FORMAT
+ }
  return s_defaultIdFormat;
  }
  set

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/LocalAppContextSwitches.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ public static bool DefaultActivityIdFormatIsHierarchial { get; } = InitializeDefaultActivityIdFormat();
+
+ private static bool InitializeDefaultActivityIdFormat()
+ {
+ bool defaultActivityIdFormatIsHierarchial = false;
+
+ if (!LocalAppContextSwitches.GetSwitchValue("System.Diagnostics.DefaultActivityIdFormatIsHierarchial", ref defaultActivityIdFormatIsHierarchial))
+ {
+ string? switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL");
+ if (switchValue != null)
+ {
+ defaultActivityIdFormatIsHierarchial = IsTrueStringIgnoreCase(switchValue) || switchValue.Equals("1");
+ }
+ }
+
+ return defaultActivityIdFormatIsHierarchial;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static bool IsTrueStringIgnoreCase(string value)
+ {
+ return value.Length == 4 &&
+ (value[0] == 't' || value[0] == 'T') &&
+ (value[1] == 'r' || value[1] == 'R') &&
+ (value[2] == 'u' || value[2] == 'U') &&
+ (value[3] == 'e' || value[3] == 'E');
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -188,32 +188,6 @@ public void ActivityIdOverflow()
  Assert.Equal('#', activity.Id[activity.Id.Length - 1]);
  }
 
- /// <summary>
- /// Tests overflow in Id generation when parentId has a single (root) node
- /// </summary>
- [Fact]
- public void ActivityIdNonHierarchicalOverflow()
- {
- // find out Activity Id length on this platform in this AppDomain
- Activity testActivity = new Activity("activity")
- .Start();
- var expectedIdLength = testActivity.Id.Length;
- testActivity.Stop();
-
- // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
- // it causes overflow during Id generation, and new root Id is generated for the new Activity
- var parentId = '|' + new string('a', 1022) + '.';
-
- var activity = new Activity("activity")
- .SetParentId(parentId)
- .Start();
-
- Assert.Equal(parentId, activity.ParentId);
-
- // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
- Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
- Assert.DoesNotContain('#', activity.Id);
- }
 
  /// <summary>
  /// Tests activity start and stop
@@ -258,6 +232,7 @@ public void IdGenerationNoParent()
  public void IdGenerationInternalParent()
  {
  var parent = new Activity("parent");
+ parent.SetIdFormat(ActivityIdFormat.Hierarchical);
  parent.Start();
  var child1 = new Activity("child1");
  var child2 = new Activity("child2");
@@ -535,11 +510,11 @@ public void ActivitySpanIdTests()
  /****** WC3 Format tests *****/
 
  [Fact]
- public void IdFormat_HierarchicalIsDefault()
+ public void IdFormat_W3CIsDefaultForNet5()
  {
  Activity activity = new Activity("activity1");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal(PlatformDetection.IsNetCore ? ActivityIdFormat.W3C : ActivityIdFormat.Hierarchical, activity.IdFormat);
  }
 
  [Fact]
@@ -617,6 +592,20 @@ public void IdFormat_W3CWhenDefaultIsW3C()
  }).Dispose();
  }
 
+ [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ public void IdFormat_WithTheEnvironmentSwitch()
+ {
+ var psi = new ProcessStartInfo();
+ psi.Environment.Add("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL", "true");
+
+ RemoteExecutor.Invoke(() =>
+ {
+ Activity activity = new Activity("activity15");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }, new RemoteInvokeOptions() { StartInfo = psi }).Dispose();
+ }
+
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
  public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  {
@@ -633,13 +622,23 @@ public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  }
 
  [Fact]
- public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ public void IdFormat_ZeroTraceIdAndSpanIdWithW3CFormat()
  {
  Activity activity = new Activity("activity");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
- Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
- Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+
+ if (PlatformDetection.IsNetCore)
+ {
+ Assert.Equal(ActivityIdFormat.W3C, activity.IdFormat);
+ Assert.NotEqual("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.NotEqual("0000000000000000", activity.SpanId.ToHexString());
+ }
+ else
+ {
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
  }
 
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/ActivityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Diagnostics.Tests
+{
+ public class ActivityTests : IDisposable
+ {
+ [Fact]
+ public void ActivityIdNonHierarchicalOverflow()
+ {
+ // find out Activity Id length on this platform in this AppDomain
+ Activity testActivity = new Activity("activity")
+ .Start();
+ var expectedIdLength = testActivity.Id.Length;
+ testActivity.Stop();
+
+ // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
+ // it causes overflow during Id generation, and new root Id is generated for the new Activity
+ var parentId = '|' + new string('a', 1022) + '.';
+
+ var activity = new Activity("activity")
+ .SetParentId(parentId)
+ .Start();
+
+ Assert.Equal(parentId, activity.ParentId);
+
+ // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
+ Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
+ Assert.DoesNotContain('#', activity.Id);
+ }
+
+ [Fact]
+ public void IdGenerationInternalParent()
+ {
+ var parent = new Activity("parent");
+ parent.Start();
+ var child1 = new Activity("child1");
+ var child2 = new Activity("child2");
+ //start 2 children in different execution contexts
+ Task.Run(() => child1.Start()).Wait();
+ Task.Run(() => child2.Start()).Wait();
+
+ // In Debug builds of System.Diagnostics.DiagnosticSource, the child operation Id will be constructed as follows
+ // "|parent.RootId.<child.OperationName.Replace(., -)>-childCount.".
+ // This is for debugging purposes to know which operation the child Id is comming from.
+ //
+ // In Release builds of System.Diagnostics.DiagnosticSource, it will not contain the operation name to keep it simple and it will be as
+ // "|parent.RootId.childCount.".
+
+ string child1DebugString = $"|{parent.RootId}.{child1.OperationName}-1.";
+ string child2DebugString = $"|{parent.RootId}.{child2.OperationName}-2.";
+ string child1ReleaseString = $"|{parent.RootId}.1.";
+ string child2ReleaseString = $"|{parent.RootId}.2.";
+
+ AssertExtensions.AtLeastOneEquals(child1DebugString, child1ReleaseString, child1.Id);
+ AssertExtensions.AtLeastOneEquals(child2DebugString, child2ReleaseString, child2.Id);
+
+ Assert.Equal(parent.RootId, child1.RootId);
+ Assert.Equal(parent.RootId, child2.RootId);
+ child1.Stop();
+ child2.Stop();
+ var child3 = new Activity("child3");
+ child3.Start();
+
+ string child3DebugString = $"|{parent.RootId}.{child3.OperationName}-3.";
+ string child3ReleaseString = $"|{parent.RootId}.3.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, child3.Id);
+
+ var grandChild = new Activity("grandChild");
+ grandChild.Start();
+
+ child3DebugString = $"{child3.Id}{grandChild.OperationName}-1.";
+ child3ReleaseString = $"{child3.Id}1.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, grandChild.Id);
+ }
+
+ [Fact]
+ public void IdFormat_HierarchicalIsDefault()
+ {
+ Activity activity = new Activity("activity1");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }
+
+ [Fact]
+ public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ {
+ Activity activity = new Activity("activity");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
+
+ public void Dispose()
+ {
+ Activity.Current = null;
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/System.Diagnostics.DiagnosticSource.Switches.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+ <TestRuntime>true</TestRuntime>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="ActivityTests.cs" />
+ </ItemGroup>
+</Project>

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+ "configProperties": {
+ "System.Diagnostics.DefaultActivityIdFormatIsHierarchial": true
+ }
+}

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -219,7 +219,7 @@
  <Compile Include="misc\GDI\DeviceContextType.cs" />
  <Compile Include="misc\GDI\WindowsGraphics.cs" />
  <Compile Include="misc\GDI\WindowsRegion.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
  Link="Common\Interop\Windows\Interop.Libraries.cs" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -403,7 +403,6 @@
  <Compile Include="$(MSBuildThisFileDirectory)System\LazyOfTTMetadata.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimization.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimizationAttribute.cs" />
- <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalDataStoreSlot.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\MarshalByRefObject.cs" />
@@ -1083,6 +1082,9 @@
  <Compile Include="$(CommonPath)SkipLocalsInit.cs">
  <Link>Common\SkipLocalsInit.cs</Link>
  </Compile>
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Compile Include="$(CommonPath)System\HResults.cs">
  <Link>Common\System\HResults.cs</Link>
  </Compile>

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -791,7 +791,7 @@
  <Compile Include="System\Xml\Xsl\Xslt\XsltLoader.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XsltQilFactory.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XslVisitor.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="System\Xml\Core\LocalAppContextSwitches.cs" />
  <Compile Include="$(CommonPath)System\CSharpHelpers.cs" />

src/libraries/System.Private.CoreLib/src/System/LocalAppContextSwitches.Common.cs → src/libraries/Common/src/System/LocalAppContextSwitches.Common.cs

@@ -11,6 +11,11 @@ namespace System
  // every framework assembly that implements any compatibility quirks.
  internal static partial class LocalAppContextSwitches
  {
+ // Returns value of given switch using provided cache.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static bool GetSwitchValue(string switchName, ref bool switchValue) =>
+ AppContext.TryGetSwitch(switchName, out switchValue);
+
  // Returns value of given switch using provided cache.
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
@@ -24,7 +29,6 @@ internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitc
 
  private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  {
-
  bool hasSwitch = AppContext.TryGetSwitch(switchName, out bool isSwitchEnabled);
  if (!hasSwitch)
  {

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -5,7 +5,6 @@
  <NoWarn>$(NoWarn);SA1205</NoWarn>
  <Nullable>enable</Nullable>
  <TargetFrameworks>$(NetCoreAppCurrent);netstandard1.1;netstandard1.3;net45;net46;netstandard2.0;$(NetFrameworkCurrent)</TargetFrameworks>
- <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
  <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
  </PropertyGroup>
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -20,6 +19,7 @@
  <DefineConstants Condition="'$(TargetFramework)' != 'netstandard1.1' and '$(TargetFramework)' != 'netstandard1.3'">$(DefineConstants);EVENTSOURCE_ENUMERATE_SUPPORT</DefineConstants>
  <DefineConstants Condition="$(TargetFramework.StartsWith('net4'))">$(DefineConstants);ALLOW_PARTIALLY_TRUSTED_CALLERS;ENABLE_HTTP_HANDLER</DefineConstants>
  <ExcludeFromPackage Condition="'$(TargetFramework)' == 'netstandard2.0'">true</ExcludeFromPackage>
+ <DefineConstants Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">$(DefineConstants);W3C_DEFAULT_ID_FORMAT</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
  <Compile Include="System\Diagnostics\DiagnosticSource.cs" />
@@ -48,6 +48,12 @@
  <Reference Include="System.Runtime.CompilerServices.Unsafe" />
  <None Include="ActivityUserGuide.md" />
  </ItemGroup>
+ <ItemGroup Condition=" '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+ <Compile Include="System\Diagnostics\LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
+ </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' != 'net45' And '$(TargetFramework)' != 'netstandard1.1'">
  <Compile Include="System\Diagnostics\Activity.Current.net46.cs" />
  </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -51,7 +51,7 @@ public partial class Activity : IDisposable
  private static ActivityIdFormat s_defaultIdFormat;
  /// <summary>
  /// Normally if the ParentID is defined, the format of that is used to determine the
- /// format used by the Activity. However if ForceDefaultFormat is set to true, the
+ /// format used by the Activity. However if ForceDefaultFormat is set to true, the
  /// ID format will always be the DefaultIdFormat even if the ParentID is define and is
  /// a different format.
  /// </summary>
@@ -735,7 +735,13 @@ public static ActivityIdFormat DefaultIdFormat
  get
  {
  if (s_defaultIdFormat == ActivityIdFormat.Unknown)
+ {
+#if W3C_DEFAULT_ID_FORMAT
+ s_defaultIdFormat = LocalAppContextSwitches.DefaultActivityIdFormatIsHierarchial ? ActivityIdFormat.Hierarchical : ActivityIdFormat.W3C;
+#else
  s_defaultIdFormat = ActivityIdFormat.Hierarchical;
+#endif // W3C_DEFAULT_ID_FORMAT
+ }
  return s_defaultIdFormat;
  }
  set

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/LocalAppContextSwitches.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ public static bool DefaultActivityIdFormatIsHierarchial { get; } = InitializeDefaultActivityIdFormat();
+
+ private static bool InitializeDefaultActivityIdFormat()
+ {
+ bool defaultActivityIdFormatIsHierarchial = false;
+
+ if (!LocalAppContextSwitches.GetSwitchValue("System.Diagnostics.DefaultActivityIdFormatIsHierarchial", ref defaultActivityIdFormatIsHierarchial))
+ {
+ string? switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL");
+ if (switchValue != null)
+ {
+ defaultActivityIdFormatIsHierarchial = IsTrueStringIgnoreCase(switchValue) || switchValue.Equals("1");
+ }
+ }
+
+ return defaultActivityIdFormatIsHierarchial;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static bool IsTrueStringIgnoreCase(string value)
+ {
+ return value.Length == 4 &&
+ (value[0] == 't' || value[0] == 'T') &&
+ (value[1] == 'r' || value[1] == 'R') &&
+ (value[2] == 'u' || value[2] == 'U') &&
+ (value[3] == 'e' || value[3] == 'E');
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -188,32 +188,6 @@ public void ActivityIdOverflow()
  Assert.Equal('#', activity.Id[activity.Id.Length - 1]);
  }
 
- /// <summary>
- /// Tests overflow in Id generation when parentId has a single (root) node
- /// </summary>
- [Fact]
- public void ActivityIdNonHierarchicalOverflow()
- {
- // find out Activity Id length on this platform in this AppDomain
- Activity testActivity = new Activity("activity")
- .Start();
- var expectedIdLength = testActivity.Id.Length;
- testActivity.Stop();
-
- // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
- // it causes overflow during Id generation, and new root Id is generated for the new Activity
- var parentId = '|' + new string('a', 1022) + '.';
-
- var activity = new Activity("activity")
- .SetParentId(parentId)
- .Start();
-
- Assert.Equal(parentId, activity.ParentId);
-
- // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
- Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
- Assert.DoesNotContain('#', activity.Id);
- }
 
  /// <summary>
  /// Tests activity start and stop
@@ -258,6 +232,7 @@ public void IdGenerationNoParent()
  public void IdGenerationInternalParent()
  {
  var parent = new Activity("parent");
+ parent.SetIdFormat(ActivityIdFormat.Hierarchical);
  parent.Start();
  var child1 = new Activity("child1");
  var child2 = new Activity("child2");
@@ -535,11 +510,11 @@ public void ActivitySpanIdTests()
  /****** WC3 Format tests *****/
 
  [Fact]
- public void IdFormat_HierarchicalIsDefault()
+ public void IdFormat_W3CIsDefaultForNet5()
  {
  Activity activity = new Activity("activity1");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal(PlatformDetection.IsNetCore ? ActivityIdFormat.W3C : ActivityIdFormat.Hierarchical, activity.IdFormat);
  }
 
  [Fact]
@@ -617,6 +592,20 @@ public void IdFormat_W3CWhenDefaultIsW3C()
  }).Dispose();
  }
 
+ [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ public void IdFormat_WithTheEnvironmentSwitch()
+ {
+ var psi = new ProcessStartInfo();
+ psi.Environment.Add("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL", "true");
+
+ RemoteExecutor.Invoke(() =>
+ {
+ Activity activity = new Activity("activity15");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }, new RemoteInvokeOptions() { StartInfo = psi }).Dispose();
+ }
+
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
  public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  {
@@ -633,13 +622,23 @@ public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  }
 
  [Fact]
- public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ public void IdFormat_ZeroTraceIdAndSpanIdWithW3CFormat()
  {
  Activity activity = new Activity("activity");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
- Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
- Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+
+ if (PlatformDetection.IsNetCore)
+ {
+ Assert.Equal(ActivityIdFormat.W3C, activity.IdFormat);
+ Assert.NotEqual("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.NotEqual("0000000000000000", activity.SpanId.ToHexString());
+ }
+ else
+ {
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
  }
 
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/ActivityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Diagnostics.Tests
+{
+ public class ActivityTests : IDisposable
+ {
+ [Fact]
+ public void ActivityIdNonHierarchicalOverflow()
+ {
+ // find out Activity Id length on this platform in this AppDomain
+ Activity testActivity = new Activity("activity")
+ .Start();
+ var expectedIdLength = testActivity.Id.Length;
+ testActivity.Stop();
+
+ // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
+ // it causes overflow during Id generation, and new root Id is generated for the new Activity
+ var parentId = '|' + new string('a', 1022) + '.';
+
+ var activity = new Activity("activity")
+ .SetParentId(parentId)
+ .Start();
+
+ Assert.Equal(parentId, activity.ParentId);
+
+ // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
+ Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
+ Assert.DoesNotContain('#', activity.Id);
+ }
+
+ [Fact]
+ public void IdGenerationInternalParent()
+ {
+ var parent = new Activity("parent");
+ parent.Start();
+ var child1 = new Activity("child1");
+ var child2 = new Activity("child2");
+ //start 2 children in different execution contexts
+ Task.Run(() => child1.Start()).Wait();
+ Task.Run(() => child2.Start()).Wait();
+
+ // In Debug builds of System.Diagnostics.DiagnosticSource, the child operation Id will be constructed as follows
+ // "|parent.RootId.<child.OperationName.Replace(., -)>-childCount.".
+ // This is for debugging purposes to know which operation the child Id is comming from.
+ //
+ // In Release builds of System.Diagnostics.DiagnosticSource, it will not contain the operation name to keep it simple and it will be as
+ // "|parent.RootId.childCount.".
+
+ string child1DebugString = $"|{parent.RootId}.{child1.OperationName}-1.";
+ string child2DebugString = $"|{parent.RootId}.{child2.OperationName}-2.";
+ string child1ReleaseString = $"|{parent.RootId}.1.";
+ string child2ReleaseString = $"|{parent.RootId}.2.";
+
+ AssertExtensions.AtLeastOneEquals(child1DebugString, child1ReleaseString, child1.Id);
+ AssertExtensions.AtLeastOneEquals(child2DebugString, child2ReleaseString, child2.Id);
+
+ Assert.Equal(parent.RootId, child1.RootId);
+ Assert.Equal(parent.RootId, child2.RootId);
+ child1.Stop();
+ child2.Stop();
+ var child3 = new Activity("child3");
+ child3.Start();
+
+ string child3DebugString = $"|{parent.RootId}.{child3.OperationName}-3.";
+ string child3ReleaseString = $"|{parent.RootId}.3.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, child3.Id);
+
+ var grandChild = new Activity("grandChild");
+ grandChild.Start();
+
+ child3DebugString = $"{child3.Id}{grandChild.OperationName}-1.";
+ child3ReleaseString = $"{child3.Id}1.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, grandChild.Id);
+ }
+
+ [Fact]
+ public void IdFormat_HierarchicalIsDefault()
+ {
+ Activity activity = new Activity("activity1");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }
+
+ [Fact]
+ public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ {
+ Activity activity = new Activity("activity");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
+
+ public void Dispose()
+ {
+ Activity.Current = null;
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/System.Diagnostics.DiagnosticSource.Switches.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+ <TestRuntime>true</TestRuntime>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="ActivityTests.cs" />
+ </ItemGroup>
+</Project>

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+ "configProperties": {
+ "System.Diagnostics.DefaultActivityIdFormatIsHierarchial": true
+ }
+}

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -219,7 +219,7 @@
  <Compile Include="misc\GDI\DeviceContextType.cs" />
  <Compile Include="misc\GDI\WindowsGraphics.cs" />
  <Compile Include="misc\GDI\WindowsRegion.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
  Link="Common\Interop\Windows\Interop.Libraries.cs" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -403,7 +403,6 @@
  <Compile Include="$(MSBuildThisFileDirectory)System\LazyOfTTMetadata.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimization.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimizationAttribute.cs" />
- <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalDataStoreSlot.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\MarshalByRefObject.cs" />
@@ -1083,6 +1082,9 @@
  <Compile Include="$(CommonPath)SkipLocalsInit.cs">
  <Link>Common\SkipLocalsInit.cs</Link>
  </Compile>
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Compile Include="$(CommonPath)System\HResults.cs">
  <Link>Common\System\HResults.cs</Link>
  </Compile>

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -791,7 +791,7 @@
  <Compile Include="System\Xml\Xsl\Xslt\XsltLoader.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XsltQilFactory.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XslVisitor.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="System\Xml\Core\LocalAppContextSwitches.cs" />
  <Compile Include="$(CommonPath)System\CSharpHelpers.cs" />

src/libraries/System.Private.CoreLib/src/System/LocalAppContextSwitches.Common.cs → src/libraries/Common/src/System/LocalAppContextSwitches.Common.cs

@@ -11,6 +11,11 @@ namespace System
  // every framework assembly that implements any compatibility quirks.
  internal static partial class LocalAppContextSwitches
  {
+ // Returns value of given switch using provided cache.
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ internal static bool GetSwitchValue(string switchName, ref bool switchValue) =>
+ AppContext.TryGetSwitch(switchName, out switchValue);
+
  // Returns value of given switch using provided cache.
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitchValue)
@@ -24,7 +29,6 @@ internal static bool GetCachedSwitchValue(string switchName, ref int cachedSwitc
 
  private static bool GetCachedSwitchValueInternal(string switchName, ref int cachedSwitchValue)
  {
-
  bool hasSwitch = AppContext.TryGetSwitch(switchName, out bool isSwitchEnabled);
  if (!hasSwitch)
  {

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -5,7 +5,6 @@
  <NoWarn>$(NoWarn);SA1205</NoWarn>
  <Nullable>enable</Nullable>
  <TargetFrameworks>$(NetCoreAppCurrent);netstandard1.1;netstandard1.3;net45;net46;netstandard2.0;$(NetFrameworkCurrent)</TargetFrameworks>
- <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
  <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
  </PropertyGroup>
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -20,6 +19,7 @@
  <DefineConstants Condition="'$(TargetFramework)' != 'netstandard1.1' and '$(TargetFramework)' != 'netstandard1.3'">$(DefineConstants);EVENTSOURCE_ENUMERATE_SUPPORT</DefineConstants>
  <DefineConstants Condition="$(TargetFramework.StartsWith('net4'))">$(DefineConstants);ALLOW_PARTIALLY_TRUSTED_CALLERS;ENABLE_HTTP_HANDLER</DefineConstants>
  <ExcludeFromPackage Condition="'$(TargetFramework)' == 'netstandard2.0'">true</ExcludeFromPackage>
+ <DefineConstants Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">$(DefineConstants);W3C_DEFAULT_ID_FORMAT</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
  <Compile Include="System\Diagnostics\DiagnosticSource.cs" />
@@ -48,6 +48,12 @@
  <Reference Include="System.Runtime.CompilerServices.Unsafe" />
  <None Include="ActivityUserGuide.md" />
  </ItemGroup>
+ <ItemGroup Condition=" '$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+ <Compile Include="System\Diagnostics\LocalAppContextSwitches.cs" />
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
+ </ItemGroup>
  <ItemGroup Condition="'$(TargetFramework)' != 'net45' And '$(TargetFramework)' != 'netstandard1.1'">
  <Compile Include="System\Diagnostics\Activity.Current.net46.cs" />
  </ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -51,7 +51,7 @@ public partial class Activity : IDisposable
  private static ActivityIdFormat s_defaultIdFormat;
  /// <summary>
  /// Normally if the ParentID is defined, the format of that is used to determine the
- /// format used by the Activity. However if ForceDefaultFormat is set to true, the
+ /// format used by the Activity. However if ForceDefaultFormat is set to true, the
  /// ID format will always be the DefaultIdFormat even if the ParentID is define and is
  /// a different format.
  /// </summary>
@@ -735,7 +735,13 @@ public static ActivityIdFormat DefaultIdFormat
  get
  {
  if (s_defaultIdFormat == ActivityIdFormat.Unknown)
+ {
+#if W3C_DEFAULT_ID_FORMAT
+ s_defaultIdFormat = LocalAppContextSwitches.DefaultActivityIdFormatIsHierarchial ? ActivityIdFormat.Hierarchical : ActivityIdFormat.W3C;
+#else
  s_defaultIdFormat = ActivityIdFormat.Hierarchical;
+#endif // W3C_DEFAULT_ID_FORMAT
+ }
  return s_defaultIdFormat;
  }
  set

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/LocalAppContextSwitches.cs

@@ -0,0 +1,39 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System
+{
+ internal static partial class LocalAppContextSwitches
+ {
+ public static bool DefaultActivityIdFormatIsHierarchial { get; } = InitializeDefaultActivityIdFormat();
+
+ private static bool InitializeDefaultActivityIdFormat()
+ {
+ bool defaultActivityIdFormatIsHierarchial = false;
+
+ if (!LocalAppContextSwitches.GetSwitchValue("System.Diagnostics.DefaultActivityIdFormatIsHierarchial", ref defaultActivityIdFormatIsHierarchial))
+ {
+ string? switchValue = Environment.GetEnvironmentVariable("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL");
+ if (switchValue != null)
+ {
+ defaultActivityIdFormatIsHierarchial = IsTrueStringIgnoreCase(switchValue) || switchValue.Equals("1");
+ }
+ }
+
+ return defaultActivityIdFormatIsHierarchial;
+ }
+
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ private static bool IsTrueStringIgnoreCase(string value)
+ {
+ return value.Length == 4 &&
+ (value[0] == 't' || value[0] == 'T') &&
+ (value[1] == 'r' || value[1] == 'R') &&
+ (value[2] == 'u' || value[2] == 'U') &&
+ (value[3] == 'e' || value[3] == 'E');
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -188,32 +188,6 @@ public void ActivityIdOverflow()
  Assert.Equal('#', activity.Id[activity.Id.Length - 1]);
  }
 
- /// <summary>
- /// Tests overflow in Id generation when parentId has a single (root) node
- /// </summary>
- [Fact]
- public void ActivityIdNonHierarchicalOverflow()
- {
- // find out Activity Id length on this platform in this AppDomain
- Activity testActivity = new Activity("activity")
- .Start();
- var expectedIdLength = testActivity.Id.Length;
- testActivity.Stop();
-
- // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
- // it causes overflow during Id generation, and new root Id is generated for the new Activity
- var parentId = '|' + new string('a', 1022) + '.';
-
- var activity = new Activity("activity")
- .SetParentId(parentId)
- .Start();
-
- Assert.Equal(parentId, activity.ParentId);
-
- // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
- Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
- Assert.DoesNotContain('#', activity.Id);
- }
 
  /// <summary>
  /// Tests activity start and stop
@@ -258,6 +232,7 @@ public void IdGenerationNoParent()
  public void IdGenerationInternalParent()
  {
  var parent = new Activity("parent");
+ parent.SetIdFormat(ActivityIdFormat.Hierarchical);
  parent.Start();
  var child1 = new Activity("child1");
  var child2 = new Activity("child2");
@@ -535,11 +510,11 @@ public void ActivitySpanIdTests()
  /****** WC3 Format tests *****/
 
  [Fact]
- public void IdFormat_HierarchicalIsDefault()
+ public void IdFormat_W3CIsDefaultForNet5()
  {
  Activity activity = new Activity("activity1");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal(PlatformDetection.IsNetCore ? ActivityIdFormat.W3C : ActivityIdFormat.Hierarchical, activity.IdFormat);
  }
 
  [Fact]
@@ -617,6 +592,20 @@ public void IdFormat_W3CWhenDefaultIsW3C()
  }).Dispose();
  }
 
+ [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ public void IdFormat_WithTheEnvironmentSwitch()
+ {
+ var psi = new ProcessStartInfo();
+ psi.Environment.Add("DOTNET_SYSTEM_DIAGNOSTICS_DEFAULTACTIVITYIDFORMATISHIERARCHIAL", "true");
+
+ RemoteExecutor.Invoke(() =>
+ {
+ Activity activity = new Activity("activity15");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }, new RemoteInvokeOptions() { StartInfo = psi }).Dispose();
+ }
+
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
  public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  {
@@ -633,13 +622,23 @@ public void IdFormat_HierarchicalWhenDefaultIsW3CButHierarchicalParentId()
  }
 
  [Fact]
- public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ public void IdFormat_ZeroTraceIdAndSpanIdWithW3CFormat()
  {
  Activity activity = new Activity("activity");
  activity.Start();
- Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
- Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
- Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+
+ if (PlatformDetection.IsNetCore)
+ {
+ Assert.Equal(ActivityIdFormat.W3C, activity.IdFormat);
+ Assert.NotEqual("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.NotEqual("0000000000000000", activity.SpanId.ToHexString());
+ }
+ else
+ {
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
  }
 
  [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/ActivityTests.cs

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading.Tasks;
+using Xunit;
+
+namespace System.Diagnostics.Tests
+{
+ public class ActivityTests : IDisposable
+ {
+ [Fact]
+ public void ActivityIdNonHierarchicalOverflow()
+ {
+ // find out Activity Id length on this platform in this AppDomain
+ Activity testActivity = new Activity("activity")
+ .Start();
+ var expectedIdLength = testActivity.Id.Length;
+ testActivity.Stop();
+
+ // check that if parentId '|aaa...a' 1024 bytes long is set with single node (no dots or underscores in the Id)
+ // it causes overflow during Id generation, and new root Id is generated for the new Activity
+ var parentId = '|' + new string('a', 1022) + '.';
+
+ var activity = new Activity("activity")
+ .SetParentId(parentId)
+ .Start();
+
+ Assert.Equal(parentId, activity.ParentId);
+
+ // With probability 1/MaxLong, Activity.Id length may be expectedIdLength + 1
+ Assert.InRange(activity.Id.Length, expectedIdLength, expectedIdLength + 1);
+ Assert.DoesNotContain('#', activity.Id);
+ }
+
+ [Fact]
+ public void IdGenerationInternalParent()
+ {
+ var parent = new Activity("parent");
+ parent.Start();
+ var child1 = new Activity("child1");
+ var child2 = new Activity("child2");
+ //start 2 children in different execution contexts
+ Task.Run(() => child1.Start()).Wait();
+ Task.Run(() => child2.Start()).Wait();
+
+ // In Debug builds of System.Diagnostics.DiagnosticSource, the child operation Id will be constructed as follows
+ // "|parent.RootId.<child.OperationName.Replace(., -)>-childCount.".
+ // This is for debugging purposes to know which operation the child Id is comming from.
+ //
+ // In Release builds of System.Diagnostics.DiagnosticSource, it will not contain the operation name to keep it simple and it will be as
+ // "|parent.RootId.childCount.".
+
+ string child1DebugString = $"|{parent.RootId}.{child1.OperationName}-1.";
+ string child2DebugString = $"|{parent.RootId}.{child2.OperationName}-2.";
+ string child1ReleaseString = $"|{parent.RootId}.1.";
+ string child2ReleaseString = $"|{parent.RootId}.2.";
+
+ AssertExtensions.AtLeastOneEquals(child1DebugString, child1ReleaseString, child1.Id);
+ AssertExtensions.AtLeastOneEquals(child2DebugString, child2ReleaseString, child2.Id);
+
+ Assert.Equal(parent.RootId, child1.RootId);
+ Assert.Equal(parent.RootId, child2.RootId);
+ child1.Stop();
+ child2.Stop();
+ var child3 = new Activity("child3");
+ child3.Start();
+
+ string child3DebugString = $"|{parent.RootId}.{child3.OperationName}-3.";
+ string child3ReleaseString = $"|{parent.RootId}.3.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, child3.Id);
+
+ var grandChild = new Activity("grandChild");
+ grandChild.Start();
+
+ child3DebugString = $"{child3.Id}{grandChild.OperationName}-1.";
+ child3ReleaseString = $"{child3.Id}1.";
+
+ AssertExtensions.AtLeastOneEquals(child3DebugString, child3ReleaseString, grandChild.Id);
+ }
+
+ [Fact]
+ public void IdFormat_HierarchicalIsDefault()
+ {
+ Activity activity = new Activity("activity1");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ }
+
+ [Fact]
+ public void IdFormat_ZeroTraceIdAndSpanIdWithHierarchicalFormat()
+ {
+ Activity activity = new Activity("activity");
+ activity.Start();
+ Assert.Equal(ActivityIdFormat.Hierarchical, activity.IdFormat);
+ Assert.Equal("00000000000000000000000000000000", activity.TraceId.ToHexString());
+ Assert.Equal("0000000000000000", activity.SpanId.ToHexString());
+ }
+
+ public void Dispose()
+ {
+ Activity.Current = null;
+ }
+ }
+}

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/System.Diagnostics.DiagnosticSource.Switches.Tests.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+ <PropertyGroup>
+ <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+ <TestRuntime>true</TestRuntime>
+ </PropertyGroup>
+ <ItemGroup>
+ <Compile Include="ActivityTests.cs" />
+ </ItemGroup>
+</Project>

src/libraries/System.Diagnostics.DiagnosticSource/tests/TestWithConfigSwitches/runtimeconfig.template.json

@@ -0,0 +1,5 @@
+{
+ "configProperties": {
+ "System.Diagnostics.DefaultActivityIdFormatIsHierarchial": true
+ }
+}

src/libraries/System.Drawing.Common/src/System.Drawing.Common.csproj

@@ -219,7 +219,7 @@
  <Compile Include="misc\GDI\DeviceContextType.cs" />
  <Compile Include="misc\GDI\WindowsGraphics.cs" />
  <Compile Include="misc\GDI\WindowsRegion.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
  Link="Common\Interop\Windows\Interop.Libraries.cs" />

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -403,7 +403,6 @@
  <Compile Include="$(MSBuildThisFileDirectory)System\LazyOfTTMetadata.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimization.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LoaderOptimizationAttribute.cs" />
- <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalAppContextSwitches.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\LocalDataStoreSlot.cs" />
  <Compile Include="$(MSBuildThisFileDirectory)System\MarshalByRefObject.cs" />
@@ -1083,6 +1082,9 @@
  <Compile Include="$(CommonPath)SkipLocalsInit.cs">
  <Link>Common\SkipLocalsInit.cs</Link>
  </Compile>
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs">
+ <Link>Common\System\LocalAppContextSwitches.Common.cs</Link>
+ </Compile>
  <Compile Include="$(CommonPath)System\HResults.cs">
  <Link>Common\System\HResults.cs</Link>
  </Compile>

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -791,7 +791,7 @@
  <Compile Include="System\Xml\Xsl\Xslt\XsltLoader.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XsltQilFactory.cs" />
  <Compile Include="System\Xml\Xsl\Xslt\XslVisitor.cs" />
- <Compile Include="$(CoreLibSharedDir)System\LocalAppContextSwitches.Common.cs"
+ <Compile Include="$(CommonPath)System\LocalAppContextSwitches.Common.cs"
  Link="System\LocalAppContextSwitches.Common.cs" />
  <Compile Include="System\Xml\Core\LocalAppContextSwitches.cs" />
  <Compile Include="$(CommonPath)System\CSharpHelpers.cs" />