Open Stack

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Hi all,

I want to make sure that everyone is present and prepared to discuss the
one outstanding spec for Kilo: https://review.openstack.org/#/c/138444/

In the words of Jay Pipes, we are at an impasse: Jay and I prefer an
approach in which the scheduler loads up the information about the
compute nodes when it starts up, and then relies on the compute nodes to
update their status whenever an instance is create/destroyed/resized.
Sylvain prefers instead to have the hosts query that information for
every call to _get_all_host_states(), adding the instance information to
the Host object as an InstanceList attribute. I might be a little off in
my summary of the two positions, but they largely reflect the preference
for solving this issue.

IMO, the former approach is a lot closer to the ideal end result for an
independent scheduler service, whereas the latter is closer to the
current design, and would be less disruptive code-wise. The former *may*
increase the probability of race conditions in which two schedulers
simultaneously try to consume resources on the same host, but there are
several possible ways we can reduce that probability.

So please read up on that spec, and come to the meeting tomorrow
prepared to discuss it.

BTW, the latter approach is very similar to an earlier version of the
spec: https://review.openstack.org/#/c/138444/8/ . We seem to be going
in circles!

- -- 

- -- Ed Leafe
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