websockify has a zombie problem

[NeilW]

There doesn't appear to be anything in the python version of websockify that reaps zombie processes. Certainly it leaves a load in the process list when I run it up on Ubuntu.

It looks like the SIGCHLD signal has to be ignored completely:

signal.signal(signal.SIGCHLD, signal.SIG_IGN)

or there needs to be a reap loop in the do_SIGCHLD procedure using something like:

os.waitpid(-1, os.WNOHANG)

to replicate what the ignore does automatically.

HTH

NeilW

[kanaka]

Heh, I just noticed this last night. It was going to take me a while to find the correct way to reap without blocking so thank you for the solution!

Commit: 0a2f850

[NeilW]

Does the version in noVNC update directly from this commit?

[kanaka]

Commit ec2b614 in noVNC.

[kanaka]

It's not automatic but I do pull changes back and forth for shared code. If git submodule support was more automatic (i.e. by default on clone/pull) I would just use that.

[NeilW]

BTW: the reaper really needs to be in a loop to catch the odd occasion where you get a SIGCHLD while you're in the signal handler and end up with a couple of processes in the wait queue. Had a couple of them today.

The try block is to catch the case where there are no child processes - which should never happen of course...

def top_SIGCHLD(self, sig, stack):
    # Reap zombies after calling child SIGCHLD handler
    self.do_SIGCHLD(sig, stack)
    self.vmsg("Got SIGCHLD, reaping zombies")
    try:
        result = os.waitpid(-1, os.WNOHANG)
        while result[0]:
            self.vmsg("Reaped child process %s" % result[0])
            result = os.waitpid(-1, os.WNOHANG)
    except (OSError):
        pass

[kanaka]

Heh, that certainly wasn't obvious from the waitpid man page. Got to love the subtleties of POSIX.

websockify: 6954e46

noVNC: 215ae8e