Bug 773124

Summary:	race condition when adding distros
Product:	[Retired] Beaker	Reporter:	Dan Callaghan <dcallagh>
Component:	lab controller	Assignee:	Dan Callaghan <dcallagh>
Status:	CLOSED CURRENTRELEASE	QA Contact:
Severity:	high	Docs Contact:
Priority:	low
Version:	0.8	CC:	bpeck, dcallagh, mcsontos, rmancy, stl
Target Milestone:	---
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	752869	Environment:
Last Closed:	2012-04-26 07:16:32 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Bug Depends On:	752869
Bug Blocks:

Description Dan Callaghan 2012-01-11 01:00:16 UTC

+++ This bug was initially created as a clone of Bug #752869 +++

Description of problem:
If two lab controllers try to add the same new distro at the same time only one of them will succeed.

Comment 1 Dan Callaghan 2012-01-11 01:03:08 UTC

Bug 752869 was fixed in Beaker 0.8 with a workaround: the call to add a new distro was split into two separate calls, and the first (subject to the race) was permitted to fail.

The proper fix for this bug is to use MappedObject.lazy_create, and to make that method be race-free using nested transactions.

    session.begin_nested()
    try:
        item = cls(**kwargs)
        session.commit()
    except IntegrityError:
        session.rollback()
        item = cls.query.filter_by(**kwargs).one()