If you're seeing an error in your /opt/Contrast/contrast-error.log that's similar to the example below, you might be bumping up against the thread limit set by your operating system.
SEVERE: Servlet.service() for servlet [spring] in context with path [/Contrast] threw exception [Request processing failed; nested exception is java.util.concurrent.ExecutionException: java.lang.OutOfMemoryError: unable to create new native thread] with root cause java.lang.OutOfMemoryError: unable to create new native thread at java.lang.Thread.start0(Native Method) at java.lang.Thread.start(Thread.java:714)
To address this issue, increase the number of threads that the Contrast user can start in your /etc/security/limits.d/90-nproc.conf file.
Note: To modify a system configuration file, you must have root access or the ability to sudo. Consult your System Administrator for additional details.
You can add the line
<contrast-username> soft nproc unlimited to the end of the file and restart the contrast-server using the command
sudo service contrast-server restart.