Bug#915379: anacron.service: should probably use KillMode=process
On Wed, Nov 11, 2020 at 09:34:16AM +0000, Tomas Janousek wrote:
> On Mon, Dec 03, 2018 at 01:42:58PM -0500, Boyuan Yang wrote:
> > I chose KillMode=mixed intentionally. Here's the reason: we want to stop
> > anacron service elegantly and not to abruptly kill any process inside the
> > control group. Anacron is accepting SIGUSR1 and interprets it as the request
> > to exit gracefully; it will wait till all its jobs to finish before it exits
> > by itself.
>
> Unfortunately this isn't entirely true.
>
> Anacron does wait for jobs to finish, but if any job invokes exim4's
> /usr/sbin/sendmail to send its result to the user, that sendmail forks the
> setuid /usr/sbin/exim4¹ to process the queue in the background and deliver the
> mail. Anacron doesn't wait for this forked process, and systemd kills it
> immediately, resulting in the mail not being delivered until the queue gets
> processed by something else.
Worse. If the receiving side does post-DATA checking of the message, and
systemd sends SIGKILL to the exim process on the sending side, the
receiving side might continue delivery without the sending side noticing
the confirmation (it's already dead by then). During the next exim queue
run, the message will be delivered a second time.
In this case, 5 seconds of extra wait would probably not be enough.
Greetings
Marc
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