Jfr print -events OldObjectSample pid16276.jfr The following example shows the command and an example of the output from a recording for an application with the pid 16276: When you have a recording, use the jfr tool located in the java-home/bin directory to print Old Object Sample events that contain information about potential memory leaks. $ jcmd pid JFR.dump filename=recording.jfr path-to-gc-roots=true An alternative way to get a recording is to dump it before the application runs out of memory using the jcmd tool, as shown in the following example: When the JVM runs out of memory and exits due to an OutMemoryError, a recording with the prefix hs_oom_pid is often, but not always, written to the directory in which the JVM was started. Start a recording when the application is started using the java command as shown in the following example: The overhead of Flight Recorder is very low, less than 1%, and it has been designed to be safe to have always on in production. To detect a memory leak, Flight Recorder must be running at the time that the leak occurs. Eventually, OutOfMemoryErrors may be seen. A typical symptom is that the application becomes slower after running for a long time due to frequent garbage collections. This information can be used to identify memory leaks.ĭetecting a slow memory leak can be hard. Here is a sample figure of a recording, which shows heap size issue:įlight Recorder records detailed information about the Java runtime and the Java application running in the Java runtime. To detect a memory leak focus on the Live Objects section of the page. Look at the Automated Analysis Results page. Once the recording is complete, the recording file (. Before starting a flight recording, make sure that the option Object Types + Allocation Stack Traces + Path to GC Root is selected from the Memory Leak Detection setting. Open JMC and start a Time fixed recording (profiling recording) for an hour. Open the MBean Browser tab and look for the GarbageCollectorAggregator MBean under. To inspect the live set, open JMC and connect to a JVM using the Java Management console (JMX). The live set is the amount of Java heap that is used after an old collection (all objects that are not live) and have been garbage collected. Watch if the live set of your application is increasing over time.

However, memory leaks can be detected early, even before such problems occur, by analyzing Java Flight recordings. Eventually, OutOfmemoryErrors may be seen. A typical symptom could be the application becoming slower after running for a long time due to frequent garbage collections. Detecting a slow memory leak can be hard.

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