[openstack-dev] [Nova][Scheduler] Policy Based Scheduler and Solver Scheduler

Khanh-Toan Tran khanh-toan.tran at cloudwatt.com
Wed Jan 29 12:25:14 UTC 2014

Dear all,

As promised in the Scheduler/Gantt meeting, here is our analysis on the
connection between Policy Based Scheduler and Solver Scheduler:


This document briefs the mechanism of the two schedulers and the
possibility of cooperation. It is my personal point of view only.

In a nutshell, Policy Based Scheduler allows admin to define policies for
different physical resources (an aggregate, an availability-zone, or all
infrastructure) or different (classes of) users. Admin can modify
(add/remove/modify) any policy in runtime, and the modification effect is
only in the target (e.g. the aggregate, the users) that the policy is
defined to. Solver Scheduler solves the placement of groups of instances
simultaneously by putting all the known information into a integer linear
system and uses Integer Program solver to solve the latter. Thus relation
between VMs and between VMs-computes are all accounted for.

If working together, Policy Based Scheduler can supply the filters and
weighers following the policies rules defined for different computes.
These filters and weighers can be converted into constraints & cost
function for Solver Scheduler to solve. More detailed will be found in the

I look forward for comments and hope that we can work it out.

Best regards,

Khanh-Toan TRAN

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