Bug 1302391

Summary: Nonoptimal failover strategy can lead to RPC timeout
Product: Red Hat OpenStack Reporter: Marian Krcmarik <mkrcmari>
Component: python-oslo-messagingAssignee: Victor Stinner <vstinner>
Status: CLOSED ERRATA QA Contact: Marian Krcmarik <mkrcmari>
Severity: urgent Docs Contact:
Priority: urgent    
Version: 8.0 (Liberty)CC: apevec, fdinitto, hguemar, jschluet, lhh, michele, oblaut, yeylon
Target Milestone: gaKeywords: AutomationBlocker, TestBlocker
Target Release: 8.0 (Liberty)   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: python-oslo-messaging-2.5.0-5.el7ost Doc Type: Bug Fix
Doc Text:
Oslo Messaging used the "shuffle" strategy to select a RabbitMQ host from the list of RabbitMQ servers. When a node of the cluster running RabbitMQ was restarted, each OpenStack service connected to this server reconnected to a new RabbitMQ server. Unfortunately, this strategy does not handle dead RabbitMQ servers correctly; it can try to connect to the same dead server multiple times in a row. The strategy also leads to increased reconnection time, and sometimes it may lead to RPC operations timing out because no guarantee is provided on how long the reconnection process will take. With this update, Oslo Messaging uses the "round-robin" strategy to select a RabbitMQ host. This strategy provides the least achievable reconnection time and avoids RPC timeout when a node is restarted. It also guarantees that if K of N RabbitMQ hosts are alive, it will take at most N - K + 1 attempts to successfully reconnect to the RabbitMQ cluster.
 Story Points: ---
Clone Of:
: 1311597 (view as bug list) Environment:
Last Closed: 2016-04-07 21:26:22 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:
Bug Depends On:    
Bug Blocks: 1311597    
Attachments:
Description Flags
nova-compute log none

Description Marian Krcmarik 2016-01-27 17:27:46 UTC 
Created attachment 1118849 [details]
nova-compute log

Description of problem:
I can hit the problems described in https://bugs.launchpad.net/oslo.messaging/+bug/1519851 (sometimes I believe I can see multiples unsuccessful tries to reconnect to different AMQP servers (even 11 times) on my RHOS8 setup. It take sometimes even several minutes to get reconnected after failover of a controller in HA (3 controllers setup) - see attached debug log from nova-compute.
I tested the patch from upstream bug and It seemed to help speed up, I would suggest to backport the patch which seems to be simple.

Version-Release number of selected component (if applicable):
python-oslo-messaging-2.5.0-1.el7ost.noarch

How reproducible:
Often

Steps to Reproduce:
1. Restartd one of the controller in HA OS setup.
2. Look at the nova-compute log for example and look for successful reconnection to different AQMP server

Actual results:
It takes sometimes several minutes while the OS is not operational.

Expected results:
It should take singificantly lower time.


Additional info:
Comment 2 Flavio Percoco 2016-02-10 15:47:34 UTC 
I think it's safe to backport this patch. I've proposed it upstream and I'll do the backport downstream after some feedback is provided on the upstream patch.
Comment 9 errata-xmlrpc 2016-04-07 21:26:22 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://rhn.redhat.com/errata/RHEA-2016-0603.html