This repository contains Dockerfiles for Cassandra images for general usage and OpenShift. Currently only CentOS based image is available. The CentOS image is then available on Docker Hub as centos/cassandra-3-centos7.
This container image provides a containerized packaging of the Cassandra daemon and client application. The cassandra server daemon accepts connections from clients and provides access to content from Cassandra databases on behalf of the clients. You can find more information on the Cassandra project from the project Web site (https://cassandra.apache.org/).
For this, we will assume that you are using the centos/cassandra-3-centos7 image.
If you want to set only the mandatory environment variables and store the database
in the /home/user/database directory on the host filesystem, execute the following command:
$ docker run -d -e CASSANDRA_ADMIN_PASSWORD=<password> -v /home/user/database:/var/opt/rh/sclo-cassandra3/lib/cassandra:Z centos/cassandra-3-centos7The image recognizes the following environment variables that you can set during
initialization by passing -e VAR=VALUE to the Docker run command.
| Variable name | Description |
|---|---|
| CASSANDRA_ADMIN_PASSWORD | Password for the admin user |
The following environment variables influence the Cassandra configuration file. They are all optional.
| Variable name | Description | Default |
|---|---|---|
| CASSANDRA_CLUSTER_NAME | The name of the cluster. | 'Test Cluster' |
| CASSANDRA_DISK_OPTIMIZATION_STRATEGY | The strategy for optimizing disk reads. | ssd |
| CASSANDRA_ENDPOINT_SNITCH | Cassandra uses the snitch to locate nodes and route requests. | SimpleSnitch |
| CASSANDRA_NUM_TOKENS | Defines the number of tokens randomly assigned to this node. | 256 |
| CASSANDRA_RPC_ADDRESS | The listen address for client connections. | ' ' |
| CASSANDRA_KEY_CACHE_SIZE_IN_MB | Maximum size of the key cache in memory. | ' ' |
| CASSANDRA_CONCURRENT_READS | Allows operations to queue low enough in the stack so that the OS and drives can reorder them. | 32 |
| CASSANDRA_CONCURRENT_WRITES | Writes in Cassandra are rarely I/O bound, so the ideal number of concurrent writes depends on the number of CPU cores on the node. The recommended value is 8 × number_of_cpu_cores. | 32 |
| CASSANDRA_MEMTABLE_ALLOCATION_TYPE | The method Cassandra uses to allocate and manage memtable memory. | 'heap_buffers' |
| CASSANDRA_MEMTABLE_CLEANUP_THRESHOLD | Ratio used for automatic memtable flush. | 0.5 |
| CASSANDRA_MEMTABLE_FLUSH_WRITERS | The number of memtable flush writer threads. | 1 |
| CASSANDRA_CONCURRENT_COMPACTORS | Number of concurrent compaction processes allowed to run simultaneously on a node. | ' ' |
| CASSANDRA_COMPACTION_THROUGHPUT_MB_PER_SEC | Throttles compaction to the specified Mb/second across the instance. | 16 |
| CASSANDRA_COUNTER_CACHE_SIZE_IN_MB | Maximum size of the counter cache in memory. | ' ' |
| CASSANDRA_INTERNODE_COMPRESSION | Controls whether traffic between nodes is compressed. | all |
| CASSANDRA_GC_WARN_THRESHOLD_IN_MS | Any GC pause longer than this interval is logged at the WARN level. | 1000 |
| CASSANDRA_AUTO_BOOTSTRAP | It causes new (non-seed) nodes migrate the right data to themselves automatically. | true |
More details about each variable can be found at: http://docs.datastax.com/en/cassandra/3.0/cassandra/configuration/configCassandra_yaml.html
You can also set the following mount points by passing the -v /host:/container flag to Docker.
| Volume mount point | Description |
|---|---|
| /var/opt/rh/sclo-cassandra3/lib/cassandra | Cassandra data directory |
Notice: When mouting a directory from the host into the container, ensure that the mounted directory has the appropriate permissions and that the owner and group of the directory matches the user UID or name which is running inside the container.
By default, Cassandra uses 7000 for cluster communication (7001 if SSL is enabled), 9042 for native protocol clients, and 7199 for JMX. The internode communication and native protocol ports are configurable in the Cassandra Configuration File (cassandra.yaml). The JMX port is configurable in cassandra-env.sh (through JVM options). All ports are TCP.
See http://cassandra.apache.org/doc/latest/
More on hardware requirements on https://docs.datastax.com/en/landing_page/doc/landing_page/planning/planningHardware.html
It is allowed to use custom configuration files for cassandra server.
To use custom configuration file in container it has to be mounted into /etc/opt/rh/sclo-cassandra3/cassandra/cassandra.yaml.
For example to use configuration file stored in /home/user directory use this option for docker run command:
-v /home/user/cassandra.yaml:/etc/opt/rh/sclo-cassandra3/cassandra/cassandra.yaml:Z.
To configure multiple JVM options a jvm.options file needs to be mounted into the container. For example to use
configuration file stored in /home/user directory use this option for
docker run command: -v /home/user/jvm.options:/etc/opt/rh/sclo-cassandra3/cassandra/jvm.options:Z.
The cassandra daemon in the container logs to the standard output, so the log is available in the container log. The log can be examined by running:
docker logs <container>
Dockerfile and other sources for this container image are available on https://github.com/sclorg/cassandra-container. In that repository, Dockerfile for CentOS is called Dockerfile, Dockerfile for RHEL (Work-in-progress) is called Dockerfile.rhel7.