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Bug 995041

Summary:	timeout duration for waiting for a client response is too long (when flushing commands)
Product:	Red Hat Enterprise Linux 6	Reporter:	Yonit Halperin <yhalperi>
Component:	spice-server	Assignee:	Yonit Halperin <yhalperi>
Status:	CLOSED ERRATA	QA Contact:	Desktop QE <desktop-qa-list>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	6.4	CC:	acathrow, cfergeau, dblechte, mkenneth, mkrcmari, uril
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	spice-server-0.12.4-3.el6	Doc Type:	Bug Fix
Doc Text:	Cause: Sometimes, when the queue of messages to send to the client (aka pipe) is full, the server waits for messages to be sent to the client (such that the pipe is not full). The server does not wait forever, but uses a timeout. This timeout (DISPLAY_CLIENT_TIMEOUT) was set to 150 seconds. Consequence: When the client is unresponsive, the server waits that long timeout period. Also sometimes this caused other problems. Fix: Reduce the timeout to 30 seconds Result: The server now waits only 30 seconds for unresponsive clients.	Story Points:	---
Clone Of:
Clones:	1016182 (view as bug list)		Environment:
Last Closed:	2013-11-21 07:42:28 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:
Bug Blocks:	1016182

Description Yonit Halperin 2013-08-08 12:57:30 UTC

Description of problem:

When we have to read all the pending commands from the driver's ring (red_worker.c flush_display_commands), we might need to wait for messages to be sent to the client, in case the the pipe to the client is full.
The wait timeout period was set by mistake to 150 seconds.
In case of bugs like 994175, or 977998, where the client is unresponsive, after the wait timeout expires, the server display channel disconnects from the client, and the server continues.
However, the long timeout triggers bug 994211, which can explain some of the server errors encountered in bug 964136.
Reducing the timeout to a more reasonable period (e.g. 30 seconds), will disconnect the display channel, and the server should continue normally, without
hitting bug 994211.


Steps to Reproduce:
Not 100% reproducible.
You can try disconnecting the client implicitly, by turning the client machine to sleep mode, or by disconnecting the network cable. Try to do the disconnection while there are ongoing changes made to the display.

Comment 1 Uri Lublin 2013-08-14 10:23:09 UTC

Upstream Patch:
http://cgit.freedesktop.org/spice/spice/commit/?id=6ced0f698507de02a67cfcd25b7ab07e8c423fad

Comment 2 Uri Lublin 2013-08-14 14:17:01 UTC

To test:
1. Connect remote-viewer to a VM.
2. Do something on the VM (e.g run a video).
3. Suspend the client (or disconnect its ethernet cable)
4. Measure the time till disconnection.
5. See if the server has errors.

Comment 4 Uri Lublin 2013-09-04 11:53:33 UTC

(In reply to Uri Lublin from comment #2)
> To test:
> 1. Connect remote-viewer to a VM.
> 2. Do something on the VM (e.g run a video).
> 3. Suspend the client (or disconnect its ethernet cable)
> 4. Measure the time till disconnection.

Most times, only the display channel is being disconnected.
When that happens a warning is logged on the server side, such as:
 SpiceWorker-Warning **  red_worker.c:9738:flush_display_commands: update timeout

> 5. See if the server has errors.


Also, note that this is not 100% reproducible (for me it was less than 10%), and may depend on what the guest is running.

Comment 6 errata-xmlrpc 2013-11-21 07:42:28 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.

http://rhn.redhat.com/errata/RHBA-2013-1571.html