Configuring Cassandra

The Cassandra configuration files location varies, depending on the type of installation:

  • docker: /etc/cassandra directory

  • tarball: conf directory within the tarball install location

  • package: /etc/cassandra directory

Cassandra’s default configuration file, cassandra.yaml, is sufficient to explore a simple single-node cluster. However, anything beyond running a single-node cluster locally requires additional configuration to various Cassandra configuration files. Some examples that require non-default configuration are deploying a multi-node cluster or using clients that are not running on a cluster node.

  • cassandra.yaml: the main configuration file for Cassandra

  • cassandra-env.sh: environment variables can be set

  • cassandra-rackdc.properties OR cassandra-topology.properties: set rack and datacenter information for a cluster

  • logback.xml: logging configuration including logging levels

  • jvm-*: a number of JVM configuration files for both the server and clients

  • commitlog_archiving.properties: set archiving parameters for the commitlog

The sample configuration files can also be found in ./conf:

  • cqlshrc.sample: how the CQL shell, cqlsh, can be configured

Main runtime properties

Configuring Cassandra is done by setting yaml properties in the cassandra.yaml file. At a minimum you should consider setting the following properties:

  • cluster_name: Set the name of your cluster.

  • seeds: A comma separated list of the IP addresses of your cluster seed nodes.

  • storage_port: Check that you don’t have the default port of 7000 blocked by a firewall.

  • listen_address: The listen address is the IP address of a node that allows it to communicate with other nodes in the cluster. Set to localhost by default. Alternatively, you can set listen_interface to tell Cassandra which interface to use, and consecutively which address to use. Set one property, not both.

  • native_transport_port: Check that you don’t have the default port of 9042 blocked by a firewall, so that clients like cqlsh can 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, like SSTables 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 default logger is logback. By default it will log:

  • INFO level in system.log

  • DEBUG level in debug.log

When running in the foreground, it will also log at INFO level to the console. You can change logging properties by editing logback.xml or by running the nodetool setlogginglevel command.