jvm-diagnostics

jvm-diagnostics provides helpful utilities and wrappers for getting diagnostics or profiling data from the running JVM.

Total Safepoint Time

The JvmDiagnostics class provides access to the JVM total safepoint time value without using reflection hacks that fail in newer java releases.

Usage

Optional<SafepointTimeAccessor> maybeSafepointAccessor = JvmDiagnostics.totalSafepointTime();
if (maybeSafepointAccessor.isPresent()) {
    SafepointTimeAccessor safepointAccessor = maybeSafepointAccessor.get();
    long safepointMillis = maybeSafepointAccessor.safepointTimeMilliseconds();
    return safepointMillis;
}
return -1L;

JFR Streaming Wrappers

The EventStreams and RecordingStreams classes provide runtime wrappers around the JFR Streaming APIs introduced in Java 14. These wrappers allow you to leverage JFR Streaming when deploying on runtimes that support it, while maintaining language or runtime compatibility with older JVMs in your codebase.

The implementation uses reflection to delegate to the streaming API classes when the runtime supports it. This is detected by factory methods in EventStreams and RecordingStreams, which will return an Optional containing an object shaped like jdk.jfr.consumer.EventStream or jdk.jfr.consumer.RecordingStream, respectively, or will return an Optional.empty() when the runtime does not support JFR Streaming.

Usage

EventStreams provides a wrapper around jdk.jfr.consumer.EventStream. To hook into the JFR repository of the current JVM (assuming there is one):

Optional<EventStreamSupport> maybeSupport = EventStreams.openRepository();
if (maybeSupport.isPresent()) {
    EventStreamSupport eventStream = maybeSupport.get();
    eventStream.onEvent("jdk.GarbageCollection", (event) -> {
        System.out.println("JVM Garbage Collection Event");
    });
    eventStream.startAsync();
}

RecordingStreams provides a similar wrapper around jdk.jfr.consumer.RecordingStream, which can be used to create a JFR recording for the current JVM. Example:

Optional<RecordingStreamSupport> maybeSupport = RecordingStreams.newRecordingStream();
if (maybeSupport.isPresent()) {
    RecordingStreamSupport recordingStream = recordingStreamSupport.get();
    recordingStream.enable("jdk.GarbageCollection");
    recordingStream.onEvent("jdk.GarbageCollection", (event) -> {
        System.out.println("JVM Garbage Collection Event");
    });
    recordingStream.startAsync();
}

See the JDK documentation on EventStream and RecordingStream for more information.