After upgrading from Apache 2.2.6 to Apache 2.2.9, when gracefully shutting
down one of our Embedded Tomcats on our application
server, we notice a temporary outage (503) from our proxy balancer before the
Hot Standby (status=+H) takes over.
Layout:
- Application proxy server (Apache 2.2.9)
- Proxies requests via mod_proxy/mod_proxy_balancer/mod_proxy_ajp to
application server
- Application server (Java)
- Runs master Java application server with Embedded Tomcat (Tomcat/5.5.17)
on port 8009
- Runs slave Java application server with Embedded Tomcat (Tomcat/5.5.17) on
port 8008
When the application proxy server was Apache 2.2.6, we were able to gracefully
shutdown the master Tomcat server (calling
embedded.stop()), and the Hot Standby (status=+H) BalancerMember would
immediately start serving requests. After the upgrade to
2.2.9, we see "HTTP/1.1 503 This application is not currently available" while
the active BalancerMember is shutting down before the
Hot Standby takes over (~ 1 second). These errors appear in both the Tomcat
access log and the Apache access log.
I have recompiled and tested Apache versions 2.2.6, 2.2.8, 2.2.9 and 2.2.11 to
verify that this problem exists at some point after
version 2.2.6. I still had the problem when switching the BalancerMember
protocol from ajp:// to http://, so I think this rules out
AJP-specific issues. I was unable to reproduce the problem using Apache
servers as the BalancerMembers, so I'm speculating this has
something to do with the interaction with Tomcat.
Please let me know what other information would be helpful in resolving this
issue.
Proxy conf:
=================================
ProxyPassMatch /(.+/)?application.server$
balancer://production_server
<Proxy balancer://production_server/>
BalancerMember ajp://server.domain.tld:8009/ lbset=1 retry=10
loadfactor=100
BalancerMember ajp://server.domain.tld:8008/ lbset=2 retry=10
status=+H
ProxySet lbmethod=bytraffic
</Proxy>
=================================
Thanks,
Michael
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