On 9/28/2011 7:25 PM, Sam Hokin wrote:
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
Stuff in lots more 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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