In this tutorial we are going to understand in detail about Tomcat Performance Tuning in Production Server.

If you used Tomcat server for your production, then this article gives you some aspects to improve the performance of the Tomcat Server. In generally my assumption is that latest release of Tomcat gives the better performance and stability when compared to Old version. The following steps are used to improve the performance of the tomcat server,

Step 1 – Increase JVM heap memory

If you had used tomcat, definitely you would have heard about “Permgen Space” error. Simply said “OutOfMemoryError”. Mostly this error will occur in the production environment. The reason for this error is tomcat has very small memory for the running process, this error can be resolved by doing some changes in the Tomcat configuration file named “catalina.bat(In windows)/catalina.sh(In Linux)”. The changes to be made is to increase the JVM heap memory.

That is , the JVM does not invoke the garbage collector often, so the server can focus more in serving web requests and the requests are completed faster. The file(catalina.sh) to be changed is located at “\tomcat server folder\bin\catalina.sh” and the configuration to be made in this file is given below,

JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8
-server -Xms1024m -Xmx1024m
-XX:NewSize=512m -XX:MaxNewSize=512m -XX:PermSize=512m
-XX:MaxPermSize=512m -XX:+DisableExplicitGC"

-Xms – Specifies the initial heap memory -Xmx – Specifies the maximum heap memory The changes will gets activated, Once you restart the Tomcat Server. Next we shall see how to handle the memory leak,

Step 2 – Resolve JRE memory leaks

Another main reason for the performance lack is memory leak, as I said before always use the latest tomcat server to get better performance and scalability. Now the phrase becomes true. This error can be resolved if we use the latest tomcat server version 6.0.26 and above. Since it contains a listener to handle the JRE and permgen memory leak. The listener used here is,

<listener classname="org.apache.catalina.core.JreMemoryLeakPreventionListener">
</listener>

You can find the above listener class configuration in the server.xml file which resides in “tomcat project folder/conf/server.xml”. Next we shall see how to tune the connector attribute “maxThreads”.

Step 3 – Thread pool setting

Thread pool specifies the number of web request load that comes in, So this part should be handled carefully in order to get the better performance. This can be accomplished by tuning the connector attribute “maxThreads”. The value of the maxThreads should be based on the volume of the traffic. If the value is low, then there will not be enough threads to handle all of the requests, so it undergoes in to the wait state and comes back only when an another request thread gets freed. If we set maxThreads value too high means then the Tomcat startup time will take longer. So its up to us, Put a right value in the maxThreads.

<connector port="8080" address="localhost" maxthreads="250" maxhttpheadersize="8192" emptysessionpath="true" protocol="HTTP/1.1" enablelookups="false" redirectport="8181" acceptcount="100" connectiontimeout="20000" disableuploadtimeout="true">
</connector>

In the preceding configuration, maxThreads value is given as “250”. This specifies the maximum number of simultaneous requests that can be handled by the server. If not specified, the default value of this attribute “200”. Any further simultaneous requests will receive “connection refused” errors until the another request gets freed. The error looks like the below,

org.apache.tomcat.util.threads.ThreadPool logFull SEVERE: All threads (250) are
currently busy, waiting. Increase maxThreads (250) or check the servlet status

If the application results in the above error, Always investigate whether the above error caused by a single request that takes too long. The reason is, Sometimes if the database connection is not released means, it will not allow to process additional request.

Note: If the number of request exceeds “750” means, Instead of setting the value “750” in the

maxThreads attribute, Its better to go for the “Tomcat Clustering” with multiple tomcat instances. That is, In the case of “1000” request, set “maxThreads=500” for the two instances of tomcat, Instead of a single Tomcat with maxThreads=1000.

Step 4 – Compression

Tomcat has an option to compress the mime-types by doing some configuration in the server.xml file. This compression should be done in the connector like the below,

<connector port="8080" protocol="HTTP/1.1" connectiontimeout="20000" redirectport="8181" compression="500" compressablemimetype="text/html,text/xml,text/plain,application/octet-stream">
</connector>

In the preceding configuration, the files will be compressed when the number of bytes is >= 500. If the files not to be compressed by the size means, Set the attribute compression=”on”. Otherwise the default the setting in Tomcat is “off”. Next we shall see, How to tune the database.

Step 5- Database performance tuning

Tomcats performance gets lacked while waiting for the database queries to get executed. Nowadays most of the application uses Relational databases, which may contains “NamedQueries”. If so, by default the tomcat will load the named queries initially, this may increase the performance. Another important thing is, always ensure that all the database connections are closed properly. Also setting the correct value in the database connection pool is very essential.

I mean the values in maxIdle, maxActive, and maxWait attributes of the Resource element. Since the configuration depends on the application requirements, I cannot specify the right values in this article. You can find the correct values by invoking the performance testing for the database.

Step 6 – Tomcat Native Library

Tomcat native library, “Apache Portable Runtime(APR)” provides superior scalability, performance and better integration with the native server technologies and gives optimal performance in the production environment. The installation steps is explained in the article Tomcat Native Library – (APR) Installation.

Step 7 – Other options

Some of the other options are,

• Enable the web browser cache, so that the static content which resides in the webapps folder loads faster, By doing this the performance is greatly increased.
• Tomcat server should be automatically restarted, whenever the machine starts.
• Normally HTTPS request is slow when compared to the HTTP request. But what ever if you want some good security for the application means, we should prefer HTTPS instead of HTTP.