[Koha-bugs] [Bug 35111] Background jobs worker crashes on SIGPIPE when database connection lost in Ubuntu 22.04

[bugzilla-daemon at bugs.koha-community.org]

https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=35111

--- Comment #15 from David Cook <dcook at prosentient.com.au> ---
As you can see, the SIGPIPE happens before a child process is forked. 

And since we're at line 137 we know that we've received a message from
RabbitMQ. Since the DB job is stuck in "New" and no worker can pick up the
message from RabbitMQ after this, we know that the message has been ACKed via
$conn->ack( { frame => $frame } );

So it's not the connection with RabbitMQ.

And since the stacktrace shows the SIGPIPE when the database connection is
checked to see if it's connected, I think it's pretty clear that it's the
SIGPIPE from the broken database connection causing the problem.

The restart of the database causing a consistently reproducible SIGPIPE also
shows it's the database connection in the parent process that is producing the
SIGPIPE.

In https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=35111#c7 I do some
software version comparisons which demonstrate that it is likely related to the
C client libraries. 

I will admit that I don't have 100% proof that it's the C client libraries
having different behaviours, but I think it's a pretty good hypothesis. 

--

Another thing to keep in mind is that daemons typically ignore SIGPIPE. This is
why we have no issues with the Starman daemon for instance. It's a good
practice in general, so there's no harm in adding it into this daemon. (We may
want to look at other daemons at some point as well.)

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