problem when tomcat is unreachable... 2004-01-26 - By Joe Hung
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Here is the setup. We have one http(2.0.43)+mod_jk(v1.2.5) load-balancing to
two jboss-tomcat workers (tomcat version 4.1.24).
Everything works fine under normal condition. However, when we try to simulate
a "network unreachable" scenerio to the first worker, we start to see long
pauses in the web application before it fails to the 2nd worker. After some
research, we found that, in mod_jk, there is a loop of 4 blocking connect()
trying to establish the connection to the first worker before it fails over.
Since each connect() takes 15 seconds to timeout (on solaris), it takes about 1
minute for mod_jk to fail over. Apparently that is not acceptable in real
deployment.
So we've modified the connect() to use a non-blocking connect() and specify the
select() timeout to a low value (say, 3 seconds) and change the looping to only
once. That solved our problem.
I really think this fix (configurable connect() timeout) should be checked in
to handle network unreachable problem.
opinions? suggestions?
cheers,
-joe
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