Improve the feedback when NoValidHost is raised by the Scheduler

Registered by Ed Leafe on 2015-05-29

Currently when the scheduler cannot find a host to place a newly-requested instance, there is only partial information about why the placement failed, and this is scattered among various logs, making it difficult to find. Improving this situation has been identified as a priority task for the Liberty release.

Note: there was some prior work related to this (https://blueprints.launchpad.net/nova/+spec/internal-scheduler), but it had a different focus, and has been abandoned.

Blueprint information

Status:
Complete
Approver:
John Garbutt
Priority:
Medium
Drafter:
Ed Leafe
Direction:
Approved
Assignee:
Ed Leafe
Definition:
Approved
Series goal:
Accepted for liberty
Implementation:
Implemented
Milestone target:
milestone icon 12.0.0
Started by
John Garbutt on 2015-06-23
Completed by
John Garbutt on 2015-08-28

Whiteboard

Gerrit topic: https://review.openstack.org/#q,topic:bp/no-valid-host-reporting,n,z

Addressed by: https://review.openstack.org/187739
    Improve reporting when Scheduler returns NoValidHost

Addressed by: https://review.openstack.org/192184
    Add logging when filtering returns nothing.

Addressed by: https://review.openstack.org/194204
    Add a Distinct Exception for Exceeding Max Retries

Addressed by: https://review.openstack.org/194780
    Make NoValidHost exceptions clearer

(?)

Work Items

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