How to get a heap dump from Kubernetes k8s pod?

Question

Please provide a simple step by step guide to looking into java heap dump from a Kubernetes pod.

Solution

1. Log in to the K8S and exec into the Pods where your java application is running.

kubectl exec -it herle-deployment-pod-5757d89d85-wrpc9 bash

2. get the process id (top command)

3. Create java heap dump

jmap -dump:live,format=b,file=<file_name>.bin <process_id>

Example:

jmap -dump:live,format=b,file=application_heap_dump.bin 1

4. Copy the heap dump from pod to your local machine.

kubectl cp <pod_name>:<heap_file> <your local destination directory>

Example:

kubectl cp herle-deployment-pod-5757d89d85-wrpc9:/tmp/application_heap_dump.bin /Users/amritharajherle/Desktop/application_heap_dump.bin

5. Use any memory leak analysis tool. I'm using the Eclipse's Memory Analyzer plugin.

• Open the heap dump file

• select leak suspect report

• You can check the number of objects and retained heap space. Also some possible leak suspects.

Comments

[Vineeth NG]

i am getting below error "jmap": executable file not found in $PATH": unknown command terminated with exit code 126.

[vinayhudli]

A side note: better to run jmap without "live" to prevent GC from running before heap dump

[Ankireddy Polu]

kill -3 JAVA_PID Note the process ID number of the Java process (e.g. using top, a grep on ps -axw, etc.) and send a QUIT signal to the process with the kill -QUIT or kill -3 command 1. For example:

[Gustavo Alexandre]

jmap does not exist in adoptopenjdk/openjdk8:alpine-slim java image, however it mostly likey jcmd would be there use this command jcmd 2960 GC.heap_dump c:/temp/heapdump.hprof

[Admin]

Please remove /tmp from example you provided in p.4. or add /tmp in p.3

[chandu ram]

Getting jmap not found error. Using the jdk. openjdk version "11.0.13" 2021-10-19 LTS OpenJDK Runtime Environment 21.10-(Zulu-11.52+13-linux-musl-x64)-Microsoft-Azure-restric‌​ted (build 11.0.13+8-LTS) OpenJDK 64-Bit Server VM 21.10-(Zulu-11.52+13-linux-musl-x64)-Microsoft-Azure-restric‌​ted (build 11.0.13+8-LTS, mixed mode)

[Natan Yellin]

@VineethNG if you don't have jmap present in the image then you can use either ephemeral containers or something like robusta.dev (disclaimer: I'm the maintainer). See home.robusta.dev/java for the latter