Open Stack

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On 22/10/14 02:26, Maru Newby wrote:
> We merged caching support for the metadata agent in juno, and
> backported to icehouse.  It was enabled by default in juno, but
> disabled by default in icehouse to satisfy the stable maint
> requirement of not changing functional behavior.
> 
> While performance of the agent was improved with caching enabled,
> it regressed a reported 8x when caching was disabled [1].  This
> means that by default, the caching backport severely impacts
> icehouse Neutron's performance.

If I correctly follow the degradation scenario, it's caused by
unneeded tokens requested from keystone each time a request hits
neutron metadata agent. This should be already fixed as [1] (included
in the latest 2014.1.3 release).

[1]: https://review.openstack.org/#/c/118996/

> 
> So, what is the way forward?  We definitely need to document the
> problem for both icehouse and juno.  Is documentation enough?  Or
> can we enable caching by default in icehouse?  Or remove the
> backport entirely.

If I'm correct, the issue is already solved in the latest Icehouse
release, so there seems to be no need to document the regression for
2014.1.2. But yeah, sure we could put it in its release notes just in
case.

> 
> There is also a proposal to replace the metadata agent’s use of the
> neutron client in favor of rpc [2].  There were comments on an old
> bug suggesting we didn’t want to do this [3], but assuming that we
> want this change in Kilo, is backporting even a possibility given
> that it implies a behavioral change to be useful?

We probably wouldn't consider backporting it to stable branches
because it touches RPC API, and we usually avoid it there. Anyway, it
shouldn't be an issue at all (as per my comment above).

> 
> Thanks,
> 
> 
> Maru
> 
> 
> 
> 1: https://bugs.launchpad.net/cloud-archive/+bug/1361357 2:
> https://review.openstack.org/#/c/121782 3:
> https://bugs.launchpad.net/neutron/+bug/1092043
> 
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