Getting Started with Apache Cassandra On DC/OS

Apache Cassandra is a distributed, structured storage system. Cassandra clusters are highly available, scalable, performant, and fault tolerant. DC/OS allows you to quickly configure, install, and manage Apache Cassandra clusters, so you can offer Cassandra as a managed service to your organization.

Prerequisites

A running DC/OS 1.9 cluster with 3 nodes each with 2 CPU shares, 6GB of memory and at least 15GB of disk for running Cassandra nodes and 1 node with 0.5 CPU shares, 2GB of memory for running the service scheduler.
DC/OS CLI installed and authenticated against your cluster.

Install Cassandra

Assuming you have a DC/OS cluster up and running, the first step is to install Cassandra using the DC/OS CLI:

[laptop ~]$ dcos package install cassandra
DC/OS Cassandra Service default configuration requires 3 nodes each with 1.5 CPU shares, 5376MB of memory and 11264MB of disk for running Cassandra Nodes. And, 1 node with 0.5 CPU shares, 2048MB of memory for running the service scheduler.
Continue installing? [yes/no] yes
Installing Marathon app for package [cassandra] version [1.0.25-3.0.10]
Installing CLI subcommand for package [cassandra] version [1.0.25-3.0.10]
New command available: dcos cassandra
DC/OS Apache Cassandra has been successfully installed!

	Documentation: https://docs.mesosphere.com/current/usage/service-guides/cassandra/
	Issues: https://dcosjira.atlassian.net/projects/CASSANDRA/issues

Note that while the DC/OS CLI subcommand cassandra is immediately available, it takes a few moments for Cassandra to start running in the cluster.

Validate installation

Validate that the installation added the enhanced DC/OS CLI for Cassandra:

[laptop ~]$ dcos cassandra --help-long
usage: cassandra [<flags>] <command> [<args> ...]

Deploy and manage Cassandra clusters

Flags:
  -h, --help              Show context-sensitive help (also try --help-long and
                          --help-man).
      --version           Show application version.
  -v, --verbose           Enable extra logging of requests/responses
      --info              Show short description.
      --force-insecure    Allow unverified TLS certificates when querying
                          service
      --custom-auth-token=DCOS_AUTH_TOKEN
                          Custom auth token to use when querying service
      --custom-dcos-url=DCOS_URI/DCOS_URL
                          Custom cluster URL to use when querying service
      --custom-cert-path=DCOS_CA_PATH/DCOS_CERT_PATH
                          Custom TLS CA certificate file to use when querying
                          service
      --name="cassandra"  Name of the service instance to query

Commands:
  help [<command>...]
    Show help.


  plan list
    Show all plans for this service


  plan show [<plan>]
    Display the deploy plan or the plan with the provided name


  plan start <plan> [<params>]
    Start the plan with the provided name, with optional envvars to supply to
    task


  plan stop <plan>
    Stop the plan with the provided name


  plan continue [<plan>]
    Continue the deploy plan or the plan with the provided name


  plan interrupt [<plan>]
    Interrupt the deploy plan or the plan with the provided name


  plan restart <plan> <phase> <step>
    Restart the plan with the provided name


  plan force <plan> <phase> <step>
    Force complete the plan with the provided name


  seeds
    Retrieve seed node information


  connection [<flags>]
    Provides Cassandra connection information

    --address  Provide addresses of the Cassandra nodes
    --dns      Provide dns names of the Cassandra nodes

  node describe [<task_name>]
    Describes a single node


  node list
    Lists all nodes


  node replace [<task_name>]
    Replaces a single node job, moving it to a different agent


  node restart [<task_name>]
    Restarts a single node job, keeping it on the same agent


  node status [<task_name>]
    Gets the status of a single node


  backup start [<flags>]
    Perform cluster backup via snapshot mechanism

    --backup_name=BACKUP_NAME      Name of the snapshot
    --external_location=EXTERNAL_LOCATION
                                   External location where the snapshot should
                                   be stored
    --s3_access_key=S3_ACCESS_KEY  S3 access key
    --s3_secret_key=S3_SECRET_KEY  S3 secret key
    --azure_account=AZURE_ACCOUNT  Azure storage account
    --azure_key=AZURE_KEY          Azure secret key

  backup stop
    Stops a currently running backup


  backup status
    Displays the status of the backup


  restore start [<flags>]
    Restores cluster to a previous snapshot

    --backup_name=BACKUP_NAME      Name of the snapshot to restore
    --external_location=EXTERNAL_LOCATION
                                   External location where the snapshot is
                                   stored
    --s3_access_key=S3_ACCESS_KEY  S3 access key
    --s3_secret_key=S3_SECRET_KEY  S3 secret key
    --azure_account=AZURE_ACCOUNT  Azure storage account
    --azure_key=AZURE_KEY          Azure secret key

  restore stop
    Stops a currently running restore


  restore status
    Displays the status of the restore


  cleanup start [<flags>]
    Perform cluster cleanup of deleted or moved keys

    --nodes="*"              A list of the nodes to cleanup or * for all.
    --key_spaces=KEY_SPACES  The key spaces to cleanup or empty for all.
    --column_families=COLUMN_FAMILIES
                             The column families to cleanup.

  cleanup stop
    Stops a currently running cleanup


  repair start [<flags>]
    Perform primary range anti-entropy repair

    --nodes="*"              A list of the nodes to repair or * for all.
    --key_spaces=KEY_SPACES  The key spaces to repair or empty for all.
    --column_families=COLUMN_FAMILIES
                             The column families to repair.

  repair stop
    Stops a currently running repair

In addition, you can go to the DC/OS UI to validate that the Cassandra service is running and healthy.

Perform CRUD operations

Retrieve the connection information:

[laptop ~]$ dcos cassandra connection
{
  "address": [
    "10.0.3.228:9042",
    "10.0.3.230:9042",
    "10.0.3.227:9042"
  ],
  "dns": [
    "node-0.cassandra.mesos:9042",
    "node-1.cassandra.mesos:9042",
    "node-2.cassandra.mesos:9042"
  ],
  "vip": "node.cassandra.l4lb.thisdcos.directory:9042"
}

SSH into your DC/OS cluster to connect to your Cassandra cluster:

[laptop ~]$ dcos node ssh --master-proxy --leader
[master ~]$

You are now inside your DC/OS cluster and can connect to the Cassandra cluster directly. Connect to the cluster using the cqlsh client:

[master ~]$ docker run -ti cassandra:3.0.10 cqlsh --cqlversion="3.4.0" <HOST>

Replace <HOST> with an IP from the address field, which we retrieved by running dcos cassandra connection, above:

[master ~]$ docker run -ti cassandra:3.0.10 cqlsh --cqlversion="3.4.0" 10.0.3.228
cqlsh>

You are now connected to your Cassandra cluster. Let’s create a sample keyspace called demo:

cqlsh> CREATE KEYSPACE demo WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 3 };

Next, create a sample table called map in the demo keyspace:

cqlsh> CREATE TABLE demo.map (key varchar, value varchar, PRIMARY KEY(key));

Insert some data in your table:

cqlsh> INSERT INTO demo.map(key, value) VALUES('Cassandra', 'Test One');
cqlsh> INSERT INTO demo.map(key, value) VALUES('StaticInfrastructure', 'Foo Bar');
cqlsh> INSERT INTO demo.map(key, value) VALUES('Buzz', '3.14');

Query the data back to make sure it’s persisted correctly:

cqlsh> SELECT * FROM demo.map;

 key                  | value
----------------------+-------------------------
            Cassandra | Test One
 StaticInfrastructure | Foo Bar
                 Buzz | 3.14

(3 rows)

Next, delete some data:

cqlsh> DELETE FROM demo.map where key = 'StaticInfrastructure';

Query again to ensure that the row was deleted successfully:

cqlsh> SELECT * FROM demo.map;

 key       | value
-----------+-------------------------
 Cassandra | Test One
      Buzz | 3.14

(2 rows)

Uninstall

To uninstall Cassandra:

$ dcos package uninstall cassandra

Use the framework cleaner script to remove your Cassandra instance from ZooKeeper and to destroy all data associated with it. The script requires several arguments, the values for which are derived from your service name: