Open Stack

Antoine Musso <hashar at free.fr> writes:

> Seems the bottleneck is 400 or so fetches against a single host (Zuul).
> Maybe you could use the Gerrit replication system to replicate the git
> repositories to some mirror hosts then have Zuul push its references to
> them.
>
> Since Zuul publish the git repository to fetch from (ZUUL_URL), Zuul
> could push the reference to a single mirror and give that mirror to the
> job.  One thing you would need is make sure the replication is properly
> working though.

We actually added the ability for Zuul to push to any location.  We
already know that having 400 hosts hit gerrit would just kill Gerrit, so
we pushed to our load-balanced farm of 4 git servers.  However, just
pushing all those refs to servers over ssh took an additional 20 seconds
for each change.  We could look into making ssh more efficient, but I
think that the separate merger solution is better because not only does
it help with the load for git fetches, but it can make zuul's queue
processing itself much faster and more responsive (it currently takes
zuul several minutes to process a gate reset for a very deep queue, and
it doesn't do anything else during that time but with this change, gate
resets should take seconds).

-Jim