Tomcat

Tomcat configuration

Starting Tomcat as a service in linux

Session Clustering

Terracotta Sessions for Tomcat (Website)

• Drop-in clustering, no need to code to any API
• Real time monitoring of session contents
• High-avaliability and failover
• Automatic management of object identity (no need to keep foreign keys as class attributes)
• Will cluster objects that are not serializable, a requirement for session replication in most Servlet container
• Terracotta configurator to assist in the configuration of Terracotta

• Large sessions
• Deep session graphs with small changes
• Sessions containing non-serializable objects
• Servlet code that doesn?t call HTTPSession.setAttribute when the session state changes

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Tomcat on Linux:
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GLIBC 2.2 / Linux 2.4 users should define an environment variable:
export LD_ASSUME_KERNEL=2.2.5

Memory

More on Memory (from http://www.olat.org/docu/4.X/tomcatApache.html)

Tomcat VM parameters and Operating System issues
The following virtual machine parameters should be used when starting tomcat:
    *
      -Xss256k: specify the stack size. Default is 0.5 MB which is way to much and consumes a lot of memory. This is the memory used for each thread. If you have the Instant Messaging component enabled for every logged in user four threads will be created which can result in a very high memory usage. Please note that this is stack memory and is consumed in addition to the memory you specify with the -Xms and -Xmx flags!
    *
      -Xms768m -Xmx768m: specify the amount of memory tomcat can use as a maximum. With about 200 concurrent users (Userbase 7500 users) OLAT usually requires about 300 MB. This configuration example is for a very large site. Note that in addition to the memory specified here the VM uses for every thread an additional amount of memory specified by the -Xss option.
    *
      -Djava.awt.headless=trueIf you run OLAT on a Unix/Linux box with no graphics environment started (e.g. KDE, Gnome) classes using image frame buffers will not work and throw an exception. By enabling the headless mode the jvm emulates an graphics environment.
Example configuration from the tomcat5/bin/catalina.sh file:
CATALINA_OPTS="-server -Xss256k -Xms768m -Xmx768m -Djava.net.preferIPv4Stack=true -Djava.awt.headless=true"

Source

Proxy Apache

Apache's ProxyPass directive implements what is known as an "inverse proxy," where one server sits in front of another and "hides" the back server's content by accepting requests, massaging the URL, passing it to the back server, waiting for a response, and handing it back to the client. This technique has many uses: in-house corporate servers with no direct Internet access can serve limited content to the outside world by masquerading behind a public server with a ProxyPass directive; load-balanced and fault tolerant "server farms" can serve clients through a massively cached front end box; and so forth.

There are actually two directives:

ProxyPass /visiblepath http://backserver:port/path...

This intercepts incoming client requests beginning with /visiblepath (interpreted as a Location, not a Directory), strips that part off, prepends http://backserver:port/path... instead, goes to backserver:port to satisy the request, then returns the result to the client as though it had come from Apache's own document tree.

ProxyPassReverse /visiblepath http://backserver:port/path...

This matching directive watches in the other direction! URL Redirects from backserver:port, and other responses containing a URL in the header, are automatically back-translated to begin with /visiblepath instead, so the "illusion" is preserved.