[openstack-dev] A simple way to improve nova scheduler

Boris Pavlovic boris at pavlovic.me
Fri Jul 19 14:52:55 UTC 2013


Hi all,



In Mirantis Alexey Ovtchinnikov and me are working on nova scheduler
improvements.

As far as we can see the problem, now scheduler has two major issues:


1) Scalability. Factors that contribute to bad scalability are these:

*) Each compute node every periodic task interval (60 sec by default)
updates resources state in DB.

*) On every boot request scheduler has to fetch information about all
compute nodes from DB.

2) Flexibility. Flexibility perishes due to problems with:

*) Addiing new complex resources (such as big lists of complex objects e.g.
required by PCI Passthrough
https://review.openstack.org/#/c/34644/5/nova/db/sqlalchemy/models.py)

*) Using different sources of data in Scheduler for example from cinder or
ceilometer.

(as required by Volume Affinity Filter
https://review.openstack.org/#/c/29343/)


We found a simple way to mitigate this issues by avoiding of DB usage for
host state storage.


A more detailed discussion of the problem state and one of a possible
solution can be found here:

https://docs.google.com/document/d/1_DRv7it_mwalEZzLy5WO92TJcummpmWL4NWsWf0UWiQ/edit#


Best regards,

Boris Pavlovic


Mirantis Inc.
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