Bug 210141

Summary:	XenD HTTP service serializes all requests
Product:	Red Hat Enterprise Linux 5	Reporter:	Daniel Berrangé <berrange>
Component:	xen	Assignee:	Daniel Berrangé <berrange>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	5.0	CC:	bjohnson, xen-maint
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	RHEA-2007-0635	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2007-11-07 17:06:46 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Daniel Berrangé 2006-10-10 13:07:37 UTC

Description of problem:
Libvirt talks to XenD over its HTTP service. Unfortunately the HTTP service
implementation is single-threaded, so all incoming requests are serialized. This
may not sound so bad until you consider that the 'VM Create' operation can take
anywhere from 5- 60 seconds to complete. During this time no other requests to
XenD will even be started. This means that *all* other applications using
libvirt will be blocked / hang  until the create operation completes. 

Version-Release number of selected component (if applicable):
xen-3.0.2-44

How reproducible:
Frequently

Steps to Reproduce:
1. Make a long running request to XenD (eg, a VM Create operation)
2. Attempt to make another unrelated request (eg list domains) at the same time
3.
  
Actual results:
The list domains request isn't processed until the create operation finishes

Expected results:
The requests are processed in parallel

Additional info:
I posted a prototype patch upstream to make XenD multi-threaded

http://lists.xensource.com/archives/html/xen-devel/2006-10/msg00264.html

Comment 1 Brian Stein 2006-10-25 17:23:41 UTC

We'd like this as a Beta2 blocker, but this isn't required.

Comment 2 RHEL Program Management 2006-10-25 17:25:13 UTC

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux release.  Product Management has requested further review
of this request by Red Hat Engineering.  This request is not yet committed for
inclusion in release.

Comment 5 Daniel Berrangé 2006-10-26 15:54:41 UTC

It has been posted upstream twice now, but no feedback has been forthcoming yet.

http://lists.xensource.com/archives/html/xen-devel/2006-10/msg01176.html

Comment 8 Daniel Berrangé 2007-03-27 16:26:38 UTC

Merged upstream in 12776:c287052a0a654a74153f176fbd8159cb1d75211b

http://xenbits.xensource.com/xen-unstable.hg?rev/c287052a0a65

Comment 10 Daniel Berrangé 2007-06-16 00:28:50 UTC

This is built into xen-3.0.3-29.el5 in dist-5E-qu-candidate. To test try the
following:

 1. Create a guest VM with 1 GB of RAM
 2. Crete a second guest VM 'B'
 3. Open two console windows
 4. In one run  'virsh save [guest A] /var/lib/xen/test.save
 5. At the same time as this is running, also run 'virsh dumpxml [guest B]' many
times over.

Prior to thsi fix, step 4 would 'hang' until step 3 completed. With this fix,
you should be able to run  step 4 without seeing any hang.

Comment 13 errata-xmlrpc 2007-11-07 17:06:46 UTC

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHEA-2007-0635.html