The following steps can be followed for both our Java and Tomcat offerings on Linux App Service. Note that, if you are using a custom image, you could enable webSSH and collect dumps using jcmd, if present.
1. Go to the Kudu Site of the WebApp via Advanced Tools blade:
2. Click on SSH to ssh into the Application Container:
3. Get the PID of the Java Process (your application):
[There are multiple ways to get it. We can use ps -ef | grep java| grep -v grep command, or simply run jcmd]
4. Finally, execute the following command to collect the Thread Dump and save it as a file.
jcmd <PID of Java Process> Thread.print > /home/threaddump
Similarly, to collect the heap dump, run:
jcmd <PID of Java Process> GC.heap_dump /home/heapdump
The files under /home are only persistent by default. Consider collecting the dumps under /home or in the mounted location for External Storage (if using BYOS)