Open Stack

Hi,

First, sorry for cross-posting on both dev and operator MLs but I also 
would like to get operators feedback.

So, I was reviewing the scheduler ComputeFilter and I was wondering why 
the logic should be in a filter.
We indeed already have a check on the service information each time that 
a request is coming in, which is done by 
HostManager.get_all_host_states() - basically called by 
FilterScheduler._schedule()

Instead, I think it is error-prone to leave that logic in a filter 
because it can easily be accidentally removed from the list of filters. 
Besides, the semantics of the filter is not well known and operators 
could not understand that it is filtering on a Service RPC status, not 
the real compute node behind it.

In order to keep a possibility for operators to explicitely ask the 
FilterScheduler to also filter on disabled hosts, I propose to add a 
config option which would be self-explicit.

So, I made a quick POC for showing how we could move the logic to 
HostManager [1]. Feel free to review it and share your thoughts both on 
the change and here, because I want to make sure that we get a consensus 
on the removal before really submitting anything.


[1] https://review.openstack.org/#/c/162180/

-Sylvain