Apache Cassandra

Apache Cassandra is a NoSQL multi-master database with linear scalability and no single point of failure.

Installation

Configuration

systemd unit

Logging to journald

The package logs to /var/log/cassandra/system.log by default. To instead log to journald you will need to edit the unit and set the service to run in the foreground by adding -f to the ExecStart line, and set Type to simple as the process will no longer fork.

This can be also done using a systemd drop-in file:

/etc/systemd/system/cassandra.service.d/override.conf

[Service]
Type=simple
ExecStart=
ExecStart=/usr/bin/cassandra -p /run/cassandra/cassandra.pid -f

If Cassandra was running, you will need to drain, and then restart Cassandra.

$ nodetool drain

cassandra.yaml

There is copious amounts of documentation in the default cassandra.yaml. When installed via the cassandra^AUR package, it is located in /etc/cassandra/cassandra.yaml

Basic configuration items to change

Setting the name of the cluster. This needs to be consistent for all nodes that you intend to have in this cluster.

cluster_name: 'Test Cluster'

Set the directory where cassandra will write too, below is the default that will be used if unset. If possible set this to a disk used only for storing cassandra data

data_file_directories:
    - /var/lib/cassandra/data

For the first node (the seed node) make sure to include its IP address in the seeds, and atleast 1 other node. for all other nodes, try and set a broad range of nodes in the cluster. If a node cannot connect to one of the seeds listed in this configuration at startup - it will fail to start.

seed_provider:
    - class_name: org.apache.cassandra.locator.SimpleSeedProvider
      parameters:
          - seeds: "192.168.1.53, 192.168.1.52"

set this based on what type of disk cassandra is using to store data on ssd or spinning

disk_optimization_strategy: ssd|spinning

This is the address Cassandra will listen for client connections on

listen_address: 192.168.1.51

This is the address this node will advertise itself as, ensure both your clients and nodes can reach this node on this address

broadcast_address: 192.168.1.51

This is the address used for thrift connections, set to 0.0.0.0 it will listen on all interfaces, which is fine as long as its firewalled for security

rpc_address: 0.0.0.0

Troubleshooting

If Cassandra fails to run as a service, try running Cassandra

$ cassandra

If you receive the following error:

Improperly specified VM option 'ThreadPriorityPolicy=42'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

Cassandra runs on Java 8 and starting with Cassandra 4.0.2, also on Java 11. You will need to install the proper Java and override the default JVM with a systemd drop-in file:

/etc/systemd/system/cassandra.service.d/override.conf

[Service]
Environment=JAVA_HOME=/usr/lib/jvm/java-8-openjdk

If this file already exists, simply add the Environment line into the [Service] block.