Bird upgrade kills all sessions for minutes.

[Maximilian Wilhelm]

Anno domini 2016 Ondrej Zajicek scripsit:

> On Tue, Oct 11, 2016 at 11:03:08AM +0200, Alexander Morlang wrote:

Hi,

> This behavior is mostly defined by appropriate OS distribution package
> tools and package configuration, not by BIRD itself.
[...]
> I don't really see that there is any significant difference between
> stop/upgrade/start and upgrade/restart as the time for the upgrade BIRD
> itself is insignificant. But perhaps there is some issue in package
> system that stops BIRD before upgrade of multiple packages.

The difference is between "stop/upgrade( lots of stuff)/start" and
"upgrade( lots of stuff)/stop/start" where "lots of stuff" can take a
rather long time depending what packages are update parallel to BIRD.

> > In our careful evaluation, we think, using the -R parameter of dh_installinit could ease our suffering, resulting in following patch:

> I do not think that this option will help in a general case. The option
> is supposed to be used when BGP graceful restart extensions is enabled on
> both sides and BIRD is recovering from graceful restart. It does not help
> in other cases (e.g., BGP router w/o graceful restart, OSPF router) and
> should not be used when GR recovery is not active (e.g., initial start,
> regular restart).

There seems to be a misunderstanding here :)

The -R is an option to dh_installinit, which has a fundamental effect
on how the debian script stop/start a deamon:

  -R, --restart-after-upgrade
      Do not stop the init script until after the package upgrade has
      been completed. This is different than the default behavior, which
      stops the script in the prerm, and starts it again in the postinst.

      This can be useful for daemons that should not have a possibly long
      downtime during upgrade. But you should make sure that the daemon
      will not get confused by the package being upgraded while it's
      running before using this option.


This seems to be a very good idea, indeed :)

Best
Max
-- 
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daß man den nächsten auch noch machen kann.