How to debug a deadlocked process written in golang

Issue

I have a process written in golang that runs as a daemon.

After a few days it stops producing output with no apparent reason. I think it might be an internal deadlock. If I do a strace -p <PID> I can see the line

futex(0x9aaba0, FUTEX_WAIT, 0, NULL

and apparently that call never ends. I would like to use the already running process (since I don’t know how/when to trigger the bug again) to debug the problem.

How can I see what goroutines are running and where they? How can I dump from the process whatever other information might be useful to debug the problem?

Solution

You can send any go program a QUIT signal, and it will exit with a full stack trace, showing the state of all goroutines, and how they are blocked.

As for strace, go programs are always multithreaded, so you always need to add the -f option

Answered By – JimB

Answer Checked By – Willingham (GoLangFix Volunteer)

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