https://issues.apache.org/bugzilla/show_bug.cgi?id=47011
Summary: mod_proxy/mod_proxy_balancer hot-standby
BalancerMembers not taking over immediately
Product: Apache httpd-2
Version: 2.2.8
Platform: PC
OS/Version: Linux
Status: NEW
Severity: regression
Priority: P2
Component: mod_proxy_balancer
AssignedTo: bugs@httpd.apache.org
ReportedBy: mwhite...@materialogic.com
After upgrading from Apache 2.2.6 to Apache 2.2.8 or greater, 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 2.2.8)
- 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 2.2.8, 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 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.
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>
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