Cassandra : Unable to lock JVM memory (ENOMEM)

Overview:

This article will describe one of the errors you might notice in Upsource logs. 

Symptoms: 

Upsource continuously shows "Indexing in progress" for some (all) revisions or Apache Cassandra database gets restarted on a regular basis. Going through Upsource logs you find this error: 

Unable to lock JVM memory (ENOMEM). This can result in part of the JVM being swapped out, especially with mmapped I/O enabled. Increase RLIMIT_MEMLOCK or run Cassandra as root.

Solution:

Insufficient resource limits may result in this kind of error. To prevent that, we recommend to set:

• maximum open files to 100000
• memory locking and address space limit to unlimited.
• number of processes to 32768

You can do it by adding the following lines to the /etc/security/limits.conf file:

* - memlock unlimited

* - nofile 100000

* - nproc 32768

* - as unlimited