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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.

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.

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?

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