Avoiding JVM delays caused by random number generation

The library used for random number generation in Oracle’s JVM relies on /dev/random by default for UNIX platforms. This can potentially block the WebLogic Server process because on some operating systems /dev/random waits for a certain amount of “noise” to be generated on the host machine before returning a result.

Although /dev/random is more secure, it’s recommended to use /dev/urandom if the default JVM configuration delays WebLogic Server startup. To determine if your operating system exhibits this behaviour, try displaying a portion of the file from a shell prompt: head -n 1 /dev/random

If the command returns immediately, you can use /dev/random as the default generator for JVM. If the command does not return immediately, use these steps to configure the JVM to use /dev/urandom:

  1. Open the $JAVA_HOME/jre/lib/security/java.security file in a text editor.
  2. Change the line “securerandom.source=file:/dev/random” to read: securerandom.source=file:/dev/./urandom
  3. Save your change and exit the text editor.

And because there’s a bug in JDK when you use /dev/urandom you have to set it up as /dev/./urandom

You can also set up system property “java.security.egd” which will override the securerandom.source setting.