Hi, folks. I've got what I consider to be a fairly significant production implementation of Tomcat with, currently, 89
contexts in 30 hosts on two concurrent servers. Everything works fine ... except when it doesn't. As the number of
contexts and hosts have increased, there have been more and more JVM and/or Tomcat crashes, typically a couple per week
lately, on one or both servers. The error messages vary from nothing at all in catalina.out, to exceptions regarding
database connections, to exceptions about threads. Basically, I've been trying to find some good advice on
configuration in my situation and haven't been able to find much.
In a bit more detail, the deployment is as follows:
(2) Dell 1950 8-CPU servers running Fedora 14 Linux 2.6.35, one with 2 GB RAM
and one with 4 GB RAM
(2) Tomcat 7.0.16 instances, one on each server, running clustered contexts in
"distributable" mode, under Sun JDK 1.6.0
One server runs Apache HTTPD, using mod_proxy_ajp to connect to the two Tomcat
instances and manage balancing
The other server runs PostgreSQL, the database used by the apps, which connect
to it via JNDI/JDBC connection pooling
There are a few contexts that run on only one or the other server (namely, Softslate and Searchblox, which are not
serialized to support clustering). Most contexts, which run my app, run in parallel on both servers. I've implemented
clustering to maintain site availability when a Tomcat instance goes down.
I could post up all the various JVM and Tomcat parameters, but I'm really looking for any definitive list of tips for
things to try to improve stability. If anyone has written or seen a "how-to" document on multi-host, multi-context
deployments like this, please share! Thanks!!
P.S. One option I've considered is to run KVM and run each host in its own virtual OS. To me that's a ridiculous amount
of OS overhead to deal with occasional Tomcat outages, but it probably would be one solution, much more difficult to
maintain than a single Tomcat instance per server running all the hosts and contexts. If you've had experience running
multiple Tomcat instances in separate virtual machines, I'd be curious to hear how it went.
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