Bird upgrade kills all sessions for minutes.

[Ondrej Zajicek]

On Tue, Oct 11, 2016 at 11:03:08AM +0200, Alexander Morlang wrote:
> Hi,
> 
> When we upgrade the installed packages on the Hosts, the upgrade process stops bird, does upgrades and starts bird again.

> Usually, i would expect an upgrade and a restart of the daemon after the upgrade, which would keep the time in which the host is offline rather short.

> Following questions arise:

> * is this behavior intended, or is it a unintended side effect?

> * did you consider this type of setups, when you implemented the upgrade process this disruptive?

> * Can you consider to fix it, easing the upgrade process in this type of setups?

Hi

This behavior is mostly defined by appropriate OS distribution package
tools and package configuration, not by BIRD itself.

Strictly speaking, we mainly release source packages, so binary
distribution packages are out of our scope (although we also release
an updated versions of OS distribution binary BIRD packages).

I will discuss this issue with people responsible for BIRD Debian
packages to see if there is a way to make BIRD upgrades less disruptive.

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.


> 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).

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."