Bug 1575758

Summary:	Cinder's image volume cache sync lock prevents parallel image downloading
Product:	Red Hat OpenStack	Reporter:	Alan Bishop <abishop>
Component:	openstack-cinder	Assignee:	Alan Bishop <abishop>
Status:	CLOSED ERRATA	QA Contact:	Avi Avraham <aavraham>
Severity:	medium	Docs Contact:	Kim Nylander <knylande>
Priority:	medium
Version:	10.0 (Newton)	CC:	aavraham, abishop, cschwede, eharney, knylande, nchandek, srevivo
Target Milestone:	zstream	Keywords:	Triaged, ZStream
Target Release:	8.0 (Liberty)
Hardware:	All
OS:	All
Whiteboard:
Fixed In Version:	openstack-cinder-7.0.3-15.el7ost	Doc Type:	Bug Fix
Doc Text:	Cinder uses a synchronization lock to prevent duplicate entries in the volume image cache. Prior to this update, the scope of the lock was too broad and caused simultaneous requests to create a volume from an image to compete for the lock, even when the image cache was not enabled. With this update, the synchronization lock has been updated to minimize the scope of the lock, and to take effect only when the volume image cache is enabled. As a result, simultaneous requests to create a volume from an image run in parallel when the volume image cache is disabled. When the volume image cache is enabled, locking is minimized to ensure only a single entry is created in the cache.	Story Points:	---
Clone Of:	1575720	Environment:
Last Closed:	2018-07-05 12:28:34 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1555188, 1572220, 1575130, 1575720
Bug Blocks:

Description Alan Bishop 2018-05-07 20:05:43 UTC

+++ This bug was initially created as a clone of Bug #1575720 +++

+++ This bug was initially created as a clone of Bug #1575130 +++

+++ This bug was initially created as a clone of Bug #1572220 +++

+++ This bug was initially created as a clone of Bug #1555188 +++

A synchronization lock was added to fix a problem that allowed multiple redundant entries in the image volume cache [1],[2].

[1] https://bugs.launchpad.net/cinder/+bug/1649636
[2] https://review.openstack.org/446590

Unfortunately, the scope of the lock is too broad and impacts performance in a couple of scenarios.

1) When the cache is not enabled, simultaneous attempts to download the image from glance are serialized.
2) Even when the volume image is cached, simultaneous requests to create a volume from the image are serialized.

The scope of the lock needs to be reduced to only serialize the portion of the process that results in an entry being added to the cache.

--- Additional comment from Alan Bishop on 2018-04-26 08:39:02 EDT ---

Patch has merged upstream, and needs to be backported to OSP.

--- Additional comment from Red Hat Bugzilla Rules Engine on 2018-04-26 08:39:08 EDT ---

This bugzilla has been removed from the Target Release until it has been release planned with 3-acks provided.

--- Additional comment from Jon Schlueter on 2018-05-02 12:15:29 EDT ---

raising needinfo? to rhos-flags@ asking for acks to get POST Bug to have proper acks and release flag before it lands.  If it doesn't have necessary bits or can't be acked bug might need to be moved off of POST until it's clear what is needed to move the bug forward.

--- Additional comment from Alan Bishop on 2018-05-04 16:13:51 EDT ---

The upstream patch merged in time to be included in the latest OSP-13 puddle.

--- Additional comment from Red Hat Bugzilla Rules Engine on 2018-05-04 16:14:01 EDT ---

This bugzilla has been removed from the Target Release until it has been release planned with 3-acks provided.

Comment 8 errata-xmlrpc 2018-07-05 12:28:34 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:2131