Re: [systemd-devel] Alias for SMTP providers [ie. mutually exclusive service alternatives]
On Tue, Jun 15, 2021 at 5:13 AM Kenneth Porter wrote: > > What happens if I list multiple services in a Wants= and After= clause that > are mutually exclusive (eg. sendmail/postfix/exim? How can I say "This unit > needs to send mail" without knowing which is enabled? Unfortunately "need to send mail" is not well defined.. a) does it need to talk to smtp/smpts/submission ports ? then your smtp daemon needs to socket activate properly b) Needs to execute the sendmail binary ? your sendmail command must queue your messages for "later", Otherwise your service must start after any of this services but not want any of them, bad news is it will race anyway and your app still shouldn't care about what daemon or not is handling the email so goto a) ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] Alias for SMTP providers [ie. mutually exclusive service alternatives]
--On Wednesday, June 16, 2021 11:46 AM +0300 Mantas Mikulėnas wrote: What does "needs to send mail" even mean? That /usr/sbin/sendmail can be called to queue a message? That you can talk to localhost:25? A well behaving MTA actually make /usr/sbin/sendmail work without the main mail daemon to be up. The mail is then only enqueued, but not dispatched, but that'll be done once the service is fully up. Hmm, I was going to post the same at first, but it doesn't really work in reverse -- if you want to send mail on shutdown and if the goal of After=postfix is "run my ExecStop before postfix gets stopped", then ability to queue doesn't help all that much. This isn't that intractable. The objective is to allow the message to escape the box to the next hop before shutdown. (On startup there's no issue.) So I can issue a queue flush in the ExitStop and then poll the queue for empty until a timeout (say, 5 seconds) is reached to allow the queue to drain. Admittedly this won't work on a system that's getting flooded with mail from other sources. On a lightly-loaded system, just sleeping for 2-5 seconds is enough to let the message escape. My current workflow for a reboot is to mail myself the result of uptime and then start a ping from another box to monitor when it comes back up. So I'm trying to script away from that to just looking at that server's mail folder. My bigger concern is how to use one Unit file to handle different MTAs. ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] Alias for SMTP providers [ie. mutually exclusive service alternatives]
On Wed, Jun 16, 2021 at 10:43 AM Lennart Poettering wrote: > On Di, 15.06.21 02:03, Kenneth Porter (sh...@sewingwitch.com) wrote: > > > What happens if I list multiple services in a Wants= and After= clause > that > > are mutually exclusive (eg. sendmail/postfix/exim? How can I say "This > unit > > needs to send mail" without knowing which is enabled? > > What does "needs to send mail" even mean? That /usr/sbin/sendmail can > be called to queue a message? That you can talk to localhost:25? > > A well behaving MTA actually make /usr/sbin/sendmail work without the > main mail daemon to be up. The mail is then only enqueued, but not > dispatched, but that'll be done once the service is fully up. > Hmm, I was going to post the same at first, but it doesn't really work in reverse -- if you want to send mail on shutdown and if the goal of After=postfix is "run my ExecStop before postfix gets stopped", then ability to queue doesn't help all that much. -- Mantas Mikulėnas ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] Alias for SMTP providers [ie. mutually exclusive service alternatives]
On Di, 15.06.21 02:03, Kenneth Porter (sh...@sewingwitch.com) wrote: > What happens if I list multiple services in a Wants= and After= clause that > are mutually exclusive (eg. sendmail/postfix/exim? How can I say "This unit > needs to send mail" without knowing which is enabled? What does "needs to send mail" even mean? That /usr/sbin/sendmail can be called to queue a message? That you can talk to localhost:25? A well behaving MTA actually make /usr/sbin/sendmail work without the main mail daemon to be up. The mail is then only enqueued, but not dispatched, but that'll be done once the service is fully up. A well behaving MTA would also support socket activation, so that the port 25 is already bound while the daemon tarts up. This means that no ordering for regular services is necessary. Anyway, we do not provide any generic target for this, but your distro might add that. Lennart -- Lennart Poettering, Berlin ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
Re: [systemd-devel] Alias for SMTP providers [ie. mutually exclusive service alternatives]
What happens if I list multiple services in a Wants= and After= clause that are mutually exclusive (eg. sendmail/postfix/exim? How can I say "This unit needs to send mail" without knowing which is enabled? ___ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
