`jstack` - print Java thread stack traces for a running Java process

jstack [-l] [-e] pid

Options you will use

-l: Long listing: locked ownable synchronizers (java.util.concurrent locks).
-e: Extended thread information.
-m: Mixed mode (Java and native frames). Removed from jstack in JDK 9: use jhsdb jstack --mixed.

Examples

$ sudo -u appuser jstack -l 1210 > dump1.txt

Same content as jcmd 1210 Thread.print -l.

$ grep -A1 'java.lang.Thread.State' dump1.txt | sort | uniq -c | sort -rn

Cluster threads by state and top frame.

Gotchas

Take three dumps about ten seconds apart: threads that are identical in all three are stuck; threads that move are merely busy.
A deadlock is reported explicitly at the end: "Found one Java-level deadlock:".

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