Extend JPS re-implementation to J9 family

internal-api/src/main/java/datadog/trace/util/PidHelper.java

@@ -69,23 +69,56 @@ private static String findPid() {
  return pid;
  }
 
- private static String getOSTempDir() {
- // See
- // https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-gettemppatha#remarks
- // and
- // the JDK OS-specific implementations of os::get_temp_directory(), i.e.
- // https://github.com/openjdk/jdk/blob/f50bd0d9ec65a6b9596805d0131aaefc1bb913f3/src/hotspot/os/bsd/os_bsd.cpp#L886-L904
- if (Platform.isLinux()) {
- return "/tmp/";
- } else if (Platform.isWindows()) {
- return Stream.of(System.getenv("TMP"), System.getenv("TEMP"), System.getenv("USERPROFILE"))
- .filter(String::isEmpty)
- .findFirst()
- .orElse("C:\\Windows");
- } else if (Platform.isMac()) {
- return System.getenv("TMPDIR");
+ private static String getTempDir() {
+ if (!Platform.isJ9()) {
+ // See
+ // https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-gettemppatha#remarks
+ // and
+ // the JDK OS-specific implementations of os::get_temp_directory(), i.e.
+ // https://github.com/openjdk/jdk/blob/f50bd0d9ec65a6b9596805d0131aaefc1bb913f3/src/hotspot/os/bsd/os_bsd.cpp#L886-L904
+ if (Platform.isLinux()) {
+ return "/tmp";
+ } else if (Platform.isWindows()) {
+ return Stream.of(System.getenv("TMP"), System.getenv("TEMP"), System.getenv("USERPROFILE"))
+ .filter(String::isEmpty)
+ .findFirst()
+ .orElse("C:\\Windows");
+ } else if (Platform.isMac()) {
+ return System.getenv("TMPDIR");
+ } else {
+ return System.getProperty("java.io.tmpdir");
+ }
+ } else {
+ try {
+ https: // github.com/eclipse-openj9/openj9/blob/196082df056a990756a5571bfac29585fbbfbb42/jcl/src/java.base/share/classes/openj9/internal/tools/attach/target/IPC.java#L351
+ return (String)
+ Class.forName("openj9.internal.tools.attach.target.IPC")
+ .getDeclaredMethod("getTmpDir")
+ .invoke(null);
+ } catch (Throwable t) {
+ // Fall back to constants based on J9 source code, may not have perfect coverage
+ String tmpDir = System.getProperty("java.io.tmpdir");
+ if (tmpDir != null && !tmpDir.isEmpty()) {
+ return tmpDir;
+ } else if (Platform.isWindows()) {
+ return "C:\\Documents";
+ } else {
+ return "/tmp";
+ }
+ }
+ }
+ }
+
+ private static Path getJavaProcessesDir() {
+ if (Platform.isJ9()) {
+ // J9 uses a different temporary directory AND subdirectory for storing jps / attach-related
+ // info
+ // https://github.com/eclipse-openj9/openj9/blob/196082df056a990756a5571bfac29585fbbfbb42/jcl/src/java.base/share/classes/openj9/internal/tools/attach/target/CommonDirectory.java#L94
+ return Paths.get(getTempDir(), ".com_ibm_tools_attach");
  } else {
- return System.getProperty("java.io.tmpdir");
+ // Emulating the hotspot way to enumerate the JVM processes using the perfdata file
+ // https://github.com/openjdk/jdk/blob/d7cb933b89839b692f5562aeeb92076cd25a99f6/src/hotspot/share/runtime/perfMemory.cpp#L244
+ return Paths.get(getTempDir(), "hsperfdata_" + System.getProperty("user.name"));
  }
  }
 
@@ -98,14 +131,27 @@ public static Set<String> getJavaPids() {
 
  // Some JDKs don't have jvmstat available as a module, attempt to read from the hsperfdata
  // directory instead
- try (Stream<Path> stream =
- // Emulating the hotspot way to enumerate the JVM processes using the perfdata file
- // https://github.com/openjdk/jdk/blob/d7cb933b89839b692f5562aeeb92076cd25a99f6/src/hotspot/share/runtime/perfMemory.cpp#L244
- Files.list(Paths.get(getOSTempDir(), "hsperfdata_" + System.getProperty("user.name")))) {
+ try (Stream<Path> stream = Files.list(getJavaProcessesDir())) {
  return stream
- .filter(file -> !Files.isDirectory(file))
  .map(Path::getFileName)
  .map(Path::toString)
+ .filter(
+ (name) -> {
+ // On J9, additional metadata files are present alongside files named $PID.
+ // Additionally, the contents of the ps dir are files with process ID files for
+ // Hotspot,
+ // but they are directories for J9.
+ // This also makes sense as defensive programming.
+ if (name.isEmpty()) {
+ return false;
+ }
+ for (int i = 0; i < name.length(); i++) {
+ if (!Character.isDigit(name.charAt(i))) {
+ return false;
+ }
+ }
+ return true;
+ })
  .collect(Collectors.toSet());
  } catch (IOException e) {
  log.debug("Unable to obtain Java PIDs via hsperfdata", e);