Fixes issue when monitoring a process launched via the same command line

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM

[dramos020]

Fixesdotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will now output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

[ghost]

Tagging subscribers to this area: @tarekgh, @tommcdon, @pjanotti
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Fixes dotnet/diagnostics#3366. A NullReferenceException was being thrown and caught because the CommandHandler in MetricsEventSource was being referenced before being initialized. Now custom metrics are displayed when trying to monitor a process in the same command line. Here is example output for a simple application with a custom meter that displays random values:

• Running dotnet-counters monitor --counters System.Runtime,demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [System.Runtime]
  % Time in GC since last GC (%) 0
  Allocation Rate (B / 1 sec) 16,072
  CPU Usage (%) 0
  Exception Count (Count / 1 sec) 0
  GC Committed Bytes (MB) 0
  GC Fragmentation (%) 0
  GC Heap Size (MB) 0.462
  Gen 0 GC Count (Count / 1 sec) 0
  Gen 0 Size (B) 0
  Gen 1 GC Count (Count / 1 sec) 0
  Gen 1 Size (B) 0
  Gen 2 GC Count (Count / 1 sec) 0
  Gen 2 Size (B) 0
  IL Bytes Jitted (B) 47,239
  LOH Size (B) 0
  Monitor Lock Contention Count (Count / 1 sec) 0
  Number of Active Timers 0
  Number of Assemblies Loaded 13
  Number of Methods Jitted 438
  POH (Pinned Object Heap) Size (B) 0
  ThreadPool Completed Work Item Count (Count / 1 sec) 0
  ThreadPool Queue Length 0
  ThreadPool Thread Count 0
  Time spent in JIT (ms / 1 sec) 10.01
  Working Set (MB) 25.793
  [demo_meter]
  random (Count / 1 sec)
  instance=app -793.95
  

• Running dotnet-counters monitor --counters demo_meter -- countersbug.exe will output:

  Press p to pause, r to resume, q to quit.
  Status: Running
  [demo_meter]
  random (Count / 1 sec)
  instance=app 799.513
  

Author:	dramos020
Assignees:	-
Labels:	area-System.Diagnostics.Tracing
Milestone:	-

[noahfalk]

Can you include the callstack where the NullReferenceException occurs? A lot of the changes were swapping the Log property to a local parent field so does that also mean the static Log property was not initialized at that point? I want to understand what constraints we are working within :)

[davmason]

@noahfalk we're trying to grab the original exception but running in to technical difficulties.

The reason it fails is if you start a session before the runtime starts, you see the following scenario

• MetricsEventSource static construct runs to initialize the Log object
• It calls the base EventSource constructor, which sees a session is open and calls the OnEventCommand for MetricsEventSource from inside the EventSource constructor
• Now we are calling in to MetricsEventSource before the static constructor has fully run and Log is assigned to so any call to Log will have a null reference

[noahfalk]

Got it. What if we did something like this?

1. When MetricsEventSource needs to access the command handler it can use a property and implement the property like this:

privateCommandHandlerHandler{get{if(_handler==null){Interlocked.CompareExchange(ref_handler,newCommandHandler(this),null);}returnhandler;}

2. When CommandHandler needs to access the MetricsEventSource it can do that through a property that was initialized in the CommandHandler constructor:

publicCommandHandler(MetricsEventSource parent){Parent=parent;}publicMetricsEventSourceParent{get;}// some code that needs to use parentParent.Error("Something bad happened");

[davmason]

Works for me

[dramos020]

Just made the changes that were suggested. @noahfalk@davmason

[davmason]

LGTM