How to take Thread Dump for Java Application in Kubernetes.

Get the container id of the pod.

$ kubectl get po <pod-id>  -o=jsonpath='{.status.containerStatuses[0].containerID}{"\n"}' | awk '{print substr($0, 10, 12);}'

Note	In my case there is only one container, if there are mulitple container, you can use selectors.

If you don’t have jstack or jcmd. you can use following steps to take thread dump.

Now get PIDs of Java Application in host machine.
```
$ docker top <container-id>
```
On host machine run below command to take thread dump.
```
$ kill -3 <pid>
```
Tip
By default thread dump is redirected to standard out which in our case is docker standard out which can be access using docker logs -f <container-id>

Now execute jstack or jcmd to take thread dump

$ jcmd <PID> /tmp/Thread.print or jstack <PID> > /tmp/Thread.print

Exit from the contrainer and then copy the thread dump using below command.
```
$ docker cp <container-id>:/tmp/Thread.print .
```