Jahia and entropy

Question

When a node is added in the JCR, a random UUID is generated. This randomness is usually generated by the operating system but it can be not efficient to generate these UUIDs fast enough. This problem usually occurs with VMs and containers.

Solution

To check the available entropy, you can:

• Under Linux:
  • execute the command *cat /proc/sys/kernel/random/entropy_avail* . If the result is below 1000 you might encounter some performance problems
  • execute the command *cat /dev/random | rngtest -c 1000* . It should take only a few seconds to give a result and you should only have a few "failures".

To improve this entropy you can either:

• Modify the file TOMCAT_HOME/bin/setenv.sh and add the parameter -Djava.security.egd=file:/dev/urandom to the environment variable CATALINA_OPTS
• Install the simple entropy daemon *haveged*: http://www.issihosts.com/haveged/