Enabling Cassandra logback debugging

In our pursuit for 100% centralized logging, I found myself recently settingup logback-gelf with Cassandra working. The intention was to point Cassandra’s logback config at our graylog2 install, but I had a mis-step somewhere during setup.

After beating my head against a wall for a while, I got in touch with DataStax support to see if they could advise me how to enable logback debugging in Cassandra. They obliged, I quickly found an error message pointing me in the right direction, and we are today happily using logback+GELF with our Cassandra install.

For anyone else wishing to enable logback debug mode, add the following line to your /etc/dse/cassandra/cassandra-env.sh:

JVM_OPTS="$JVM_OPTS -Dlogback.debug=true"

After that, debug output can be found in /var/log/cassandra/output.log.