Roll your own Continuous Integration System (C.I.S.): Basic Tomcat configuration - Memory

Roll your own Continuous Integration System (C.I.S.)

Content:

Abstract

Install Tomcat

Basic Tomcat configuration - Memory

Basic Tomcat configuration - JMX

Basic Tomcat configuration - Application Manager and permissions

Apache and uSVN

Installing Artifactory from WAR

Configure Artifactory and MySQL

Configuring Artifactory security and repositories

In previous post, you installed Tomcat and let it running in your computer. Now it is time for a first configuration. We are going to focus in three usual needs.

1) We need more memory, always.
2) We need to monitor our system, we will use built-in JMX server.
3) We need permissions to get the manager application run. That manager application will make it easier the deploy task in near future.

Enlarge your memory
In spite of the amount of memory your system has, Java limits some thresholds for its applications. Default size for Sun's JVM PermGen space are 64M, and this is little memory for Artifactory, Hudson or Sonar. I do not remember which gives the problem :P

Objectives:
- Avoid PermGen exceptions by classloaders or application leaks, at least, in development environment.
- Increase available memory, some of the applications we will install are really hungry. Our Continuous Integration System will do some compilations which take much memory and we will foresee that need.

• For any Linux Tomcat6: Open /usr/share/tomcat6/conf/tomcat6.conf (or $TOMCAT_HOME/conf/tomcat6.conf if you installed it in other folder).
• Check that JAVA_OPTS is not set, I mean, there is a "#" in front of every JAVA_OPTS= line or any JAVA_OPTS line exists. If it is really not set, add this line:
  
  JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 -XX:PermSize=256m -XX:MaxPermSize=256m"
  
  else, just merge available with new parameters, but if the system is just installed, it shouldn't exist.
   
• For Windows Tomcat6: Easier to find, Start->All programs->Apache Tomcat 6.0->Configure Tomcat. Then click "Java" tab.

•  Check if any of next parameters are set, I mean, if that line exists. No "#" possibility. If the parameter exists, replace with new value, else simply add.
• -Djava.awt.headless=true 
• -Dfile.encoding=UTF-8 
• -XX:PermSize=256m 
• -XX:MaxPermSize=256m

What have I added?:
All these are system parameters, they do not do anything by themselves, but that information is available for all applications and JVM. This way, when an application or the JVM itself is running, they can read system parameters and change their behavior.

java.awt.headless=true:
Headless mode is a system configuration in which the display device, keyboard, or mouse is lacking. Sounds unexpected, but actually you can perform different operations in this mode, even with graphic data.
http://java.sun.com/developer/technicalArticles/J2SE/Desktop/headless/

-Dfile.encoding=UTF-8:
You are specifying the default encoding for this JVM. From now on, if anything different is said, your applications will read and write and String will be built using that internal encoding.
By specifying this, you do not have to speculate with customer OS-dependent configuration.

-XX:PermSize=256m and -XX:MaxPermSize=256m modifies structure and behavior of JVM memory. I owe you a better explanation.


More options:
http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html

Tomcat6 performance guide:
http://tomcat.apache.org/articles/performance.pdf