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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 44736] mod_proxy_balancer looses it's mind on reloads.
Date Thu, 04 Aug 2011 20:57:04 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=44736

Robert Egglestone <r.egglestone@auckland.ac.nz> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|WONTFIX                     |

--- Comment #8 from Robert Egglestone <r.egglestone@auckland.ac.nz> 2011-08-04 20:57:04
UTC ---
The comment on the WONTFIX above suggests that the issue has been
misinterpreted.

The issue is not that local changes via balancer-manager are being lost, this
behaviour is understood.

The issue is that by making change to the configuration file (no changes to
balancer manager), and then doing a graceful restart, the routes can become
offset in a way that no longer matches the configured servers.

For example, if I have this:

<Proxy balancer://balancer1/>
  BalancerMember http://host1 route=host1
  BalancerMember http://host2 route=host2
  BalancerMember http://host3 route=host3
</Proxy>

... and I comment out host1, then do a graceful restart, I may end up with
Apache behaving like this ...

http://host2 route=host1
http://host3 route=host2


Some observed notes:

+ Problems appear when new balancer blocks are added or removed, or balancer 
members are added or removed.

+ The route names can even cross from one balancer configuration block to
another!

+ It doesn't always happen, we see it on active systems.

+ A subsequent graceful restart usually fixes the routes.

+ When it does happen, it happens consistently - we have multiple httpd servers
polling Subversion for configuration changes, then checking them out and doing
a graceful restart. In this situation, all of our httpd servers tend to develop
the same route problems at the same time.


This issue has various impacts on applications. In the worst case we saw it
cause all traffic for a balancer to be directed to a single balancer member,
which couldn't handle the load.

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