[erlang-questions] Strange interaction between Docker and Erlangs ports (exit_status lost)

Mikael Pettersson mikpelinux@REDACTED
Fri Dec 18 09:15:30 CET 2015

Lukas Larsson writes:
 > On Thu, Dec 17, 2015 at 9:16 PM, Lukas Larsson <garazdawi@REDACTED> wrote:
 > >
 > > On Thu, Dec 17, 2015 at 8:59 PM, Alexey Lebedeff <binarin@REDACTED>
 > > wrote:
 > >>
 > >> So the assumption about no extra SIGCHLD is wrong and needs to be fixed.
 > >> Are you willing to do this? Or I could give it a try.
 > >>
 > >
 > > It may actually already be fixed in master. I just did a complete rewrite
 > > of the spawn driver to be released in 19.0 and if i remember correctly it
 > > should not have this problem.
 > >
 > Looking a bit more on the internet i found this:
 > https://blog.phusion.nl/2015/01/20/docker-and-the-pid-1-zombie-reaping-problem/
 > which seems to describe exactly the problem that you are experiencing. The
 > erlang vm is not built to run as the pid 1 process, even with my new
 > changes in the master branch this will still be a problem as instead of
 > missing out on exit_status messages you will have a system full of zombie
 > processes.

To my old Unix eye it seems quite broken to suddenly run random stuff
as PID 1 with the unexpected SIGCHLDs that entails.  So to me it looks
like a nasty bug in docker itself.  Sure, the Erlang VM could try to work
around it, but frankly it shouldn't have to.

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