How can a java program find itself has experienced a long GC pause?

what is gc pause
minor gc taking long time
total time for which application threads were stopped
maxgcpausemillis
kafka gc pause
possible too long jvm pause
java 8 gc tuning
java stop-the world pause

I am writing a program that can have long GC pauses, however the SLA said I shouldn't have too many of them. And it needs to report if it finds any.

How can I make it monitor itself? I don't want to parse GC logs.

JMX exposes LastGcInfo, but I don't know when to query it.

It is not good idea to let application handle GC relate monitoring in user code space. Sometime application is in the state (close to OOM), where it won't be able to execute user code and monitoring can remain broken.

If you want to do this anyways (at your risk), you can hook the listeners to GC like this and inspect GC duration.

for (GarbageCollectorMXBean gcBean : ManagementFactory.getGarbageCollectorMXBeans()) {
    NotificationEmitter emitter = (NotificationEmitter) gcBean;
    emitter.addNotificationListener(new CustomNotificationListener(), null, null);
}

and

class CustomNotificationListener implements javax.management.NotificationListener {
        @Override
        public void handleNotification(Notification notification, Object handback) {
            // hook your logic here.
          String notifType = notification.getType();
          if (notifType.equals(GarbageCollectionNotificationInfo.GARBAGE_COLLECTION_NOTIFICATION)) {
              // retrieve the garbage collection notification information
              CompositeData cd = (CompositeData) notification.getUserData();
              GarbageCollectionNotificationInfo info = GarbageCollectionNotificationInfo.from(cd);
              System.out.println(info.getGcInfo().getDuration());
          }
        }
}

Garbage collection pauses, This article is about tuning GC for java applications using large heaps If CMS is enabled JVM will experience following types of pauses: good), but may increase pause length by increasing T. You should find balance for your application. Rather than trying to answer this myself, let me refer to Clement  I'm working with java GC implementations for a long time. Advises in this article are from my practical experience. GC economics for 2GiB heap and 10GiB heap are totally different, keep it in mind

Measure of "Suspension Time", Garbage collection is necessary, but it can be a performance killer if not done well. Take these Join the DZone community and get the full member experience. Join For Free. Long GC pauses are undesirable for applications. It affects If you find your processes are swapping, then do one of the following:. That will give you nice aggregated output on exactly how much time has been spent in GC during the lifetime of your JVM. Enable garbage collection logs. As documented, you can use -verbose:gc, -XX:+PrintGCDetails and -XX:+PrintGCTimeStamps flags. -Xloggc flag can be used to direct those to a file.

Before jumping straight to a paid Java APM application or ad-hoc implementations, take a look at Glowroot.

It is free and opensource, providing you the possibility to monitor a bunch of metrics, including GC collection time, Heap usage. It is also possible to send e-mails with alerts to you and your collaborators.

Little overhead will be noticed. I've been using it for a while for applications with little or no budget at all.

Give it a try(here is a demo), then pick an APM that suits your needs better.

The Impact of Garbage Collection on application performance, While running into a long GC pause isn't rare, this particular pause Also, prior to Java 9, GC logging had not been thread-safe, meaning the logs GC threads to accumulate kernel time, but it will if the system itself is short on memory. can help improve the performance and stability of our applications. 1 Answer 1. Before a GC can be performed, it has to get every thread to a safe point (it doesn't just stop every thread immediately). If you have long running JNI calls or system calls, it can take a long time to reach a safe point.

How to Tame Java GC Pauses? Surviving 16GiB Heap and Greater , Understanding Java Garbage Collection Logging: What Are GC Logs Once the object is no longer referenced from inside our code the memory can be The Java Virtual Machine runs the Garbage Collector in the background to find we had a young generation garbage collection event [GC pause (G1  3 Garbage Collector Implementation. One strength of the Java SE platform is that it shields the developer from the complexity of memory allocation and garbage collection. However, when garbage collection is the principal bottleneck, it's useful to understand some aspects of the implementation.

How to Reduce Long GC Pauses, One such way is to carefully track what your users are experiencing and improve based on that. We do apply this technique ourselves and have again spent some 43 JVMs (14%) faced a maximum GC pause longer than 16 seconds Did you know that GC stops 20% of Java applications regularly for  This issue is that in most runtimes that have a GC, allocating objects is a quick operation, but at some point in time the GC will need to clean up all the garbage and to do this is has to pause the entire runtime (except if you happen to be using Azul’s pauseless GC for Java). The GC needs to pause the entire runtime so that it can move around objects as part of it’s compaction phase. If these objects were being referenced by code that was simultaneously executing then all sorts of bad

Want to Know What's in a GC Pause? Go Look at the GC Log!, Before Java made garbage collection mainstream, programmers had little choice but to If the heap is fragmented, when a program tries to create an object, it will have a long search to find a chunk of free so there are no global pauses; instead, each thread will experience tiny delays. Collection itself is done by copying. Shenandoah is the low pause time garbage collector that reduces GC pause times by performing more garbage collection work concurrently with the running Java program. Shenandoah does the bulk of GC work concurrently, including the concurrent compaction, which means its pause times are no longer directly proportional to the size of the heap.

Comments
  • Have you considered using any APM-like application? Forcing an application to monitor itself and report on errors/events might not be a good choice on a scaling infrastructure.
  • How many are "too many of them"?
  • Well, the SLA didn't mention GC I believe. But my leader said I am responsible for GC pauses.
  • Good. So that means that you are not obligated your monitoring in a way that won't work. My advice to use one of the alternative ways to measure / monitor response time.