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Configuring Cassandra
---------------------

For running Cassandra on a single node, the default configuration file present at ``./conf/cassandra.yaml`` is enough, 
you shouldn't 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.