Configuring Cassandra

For running Cassandra on a single node, the steps above are enough, you don’t really need to change any configuration. However, when you deploy a cluster of nodes, or use clients that are not on the same host, then there are some parameters that must be changed.

The Cassandra configuration files can be found in the conf directory of tarballs. For packages, the configuration files will be located in /etc/cassandra.

Main runtime properties

Most of configuration in Cassandra is done via yaml properties that can be set in cassandra.yaml. At a minimum you should consider setting the following properties:

  • cluster_name: the name of your cluster.
  • seeds: a comma separated list of the IP addresses of your cluster seeds.
  • storage_port: you don’t necessarily need to change this but make sure that there are no firewalls blocking this port.
  • listen_address: the IP address of your node, this is what allows other nodes to communicate with this node so it is important that you change it. Alternatively, you can set listen_interface to tell Cassandra which interface to use, and consecutively which address to use. Set only one, not both.
  • native_transport_port: as for storage_port, make sure this port is not blocked by firewalls as clients will communicate with Cassandra on this port.

Changing the location of directories

The following yaml properties control the location of directories:

  • data_file_directories: one or more directories where data files are located.
  • commitlog_directory: the directory where commitlog files are located.
  • saved_caches_directory: the directory where saved caches are located.
  • hints_directory: the directory where hints are located.

For performance reasons, if you have multiple disks, consider putting commitlog and data files on different disks.

Environment variables

JVM-level settings such as heap size can be set in cassandra-env.sh. You can add any additional JVM command line argument to the JVM_OPTS environment variable; when Cassandra starts these arguments will be passed to the JVM.

Logging

The logger in use is logback. You can change logging properties by editing logback.xml. By default it will log at INFO level into a file called system.log and at debug level into a file called debug.log. When running in the foreground, it will also log at INFO level to the console.