[pve-devel] [RFC cluster] pmxcfs startup: order before MTAs

[Stoiko Ivanov <s.ivanov@proxmox.com>]

currently pmxcfs and the running mta (postfix in most cases I assume)
have no ordering between them - resulting in the mta starting before
pmxcfs.

This can be problematic in case of a mail for 'root' being in the
mailq: postfix tries to deliver the mail - pvemailforward tries to
look up the destination address in /etc/pve/user.cfg and gets a
connection refused since pmxcfs is not running yet.

reported via our community-forum:
https://forum.proxmox.com/threads/.108893/

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
sending as RFC, since while thinking about this issue and discussing it
off-list (thx @Fiona!) the following alternative approaches were/are
considered:
* letting pvemailforward.pl exit with an error-code - sadly does not work
  as the only difference is that postfix generates a bounce for the mail
  and in (the most-common) case of root being the sender that bounce is
  also undeliverable, and thus dropped
* the fix through systemd-ordering does work for this case - but seems
  not quite fitting (after all pmxcfs and postfix can happily exist w/o
  the other - only delivering mail to root does not work) - also
  the issue also happens if pmxcfs is not available for other reasons
* an alternative approach would be to retry fetching the information from
  pmxcfs a few times (afair postfix' command-timeout is 1000s for this),
  e.g. like we do in the installer when looking for the correct ISO.

 debian/pve-cluster.service | 1 +
 1 file changed, 1 insertion(+)

diff --git a/debian/pve-cluster.service b/debian/pve-cluster.service
index 4327055..fb706be 100644
--- a/debian/pve-cluster.service
+++ b/debian/pve-cluster.service
@@ -5,6 +5,7 @@ Wants=corosync.service
 Wants=rrdcached.service
 Before=corosync.service
 Before=cron.service
+Before=postfix.service exim4.service sendmail.service qmail.service
 After=network.target
 After=sys-fs-fuse-connections.mount
 After=time-sync.target
-- 
2.30.2