Cassandra

An example to play with Cassandra on Docker

Prerequisites

  • Have a docker account

  • Docker installed

Get the Image

  1. Docker login: $ docker login
  2. Pull cassandra image: $ docker pull cassandra:3.11.4

Start cassandra

One instance

  • $ docker run -p 9042:9042 --name cassandra-node1 -e CASSANDRA_CLUSTER_NAME=VEXCluster -d cassandra:3.11.4
    • -p 9042:9042: public the port 9042 to the host 9042
    • --name cassandra-node1: name the container
    • -e CASSANDRA_CLUSTER_NAME=VEXCluster: set the variable CASSANDRA_CLUSTER_NAME to be VEXCluster
    • -d: run the container in background (detach)

Cluster

Start the instance as described above. To start other instances, just tell each new node where the first is.

  • $ docker run --name cassandra-node2 -e CASSANDRA_SEEDS="$(docker inspect --format='{{ .NetworkSettings.IPAddress }}' cassandra-node1)" -e CASSANDRA_CLUSTER_NAME=VEXCluster -d cassandra:3.11.4

Connection

Bash

Execute the bash in the docker in an interactive way:

$ docker exec -it cassandra-example bash

cqlsh

Run cqlsh in the docker:

$ docker run -it [--network name-of-a-network] --rm cassandra:3.11.4 cqlsh cassandra-example

From the host

If we want to directly connect to the cassandra in the docerk, we have to expose the port to the host.

$ docker run -p 9042:9042 --rm --name cassandra-example -d cassandra:3.11.4

Then we can use cqlsh locally.

Update cofig

$ docker run -p 9042:9042 --rm --name cassandra-example -d cassandra:3.11.4 -Dcassandra.config=file:////docker/apth/cassandra.yaml

cqlsh

  • cqlsh version: $ show version

Keyspace

  • DESC[RIBE] KEYSPACES;
  • USE $KEYSPACE_NAME;
  • DESC[RIBE] KEYSPACE;
  • DESC[RIBE] $KEYSPACE_NAME;

Table

  • DESC[RIBE] TABLES;
  • DESC[RIBE] $TABLE_NAME;

Schema Migration

$ docker exec -it ${cassandra_container} bash
# Export a keyspace
$ cqlsh -e "DESC KEYSPACE $KEYSPACE_NAME" > user_schema.cql
# Export the entire database schema
$ cqlsh -e "DESC SCHEMA" > db_schema.cql
# Import the schema
$ docker exec -it ${cassandra_container} cqlsh
$ source `user_schema.cql`

Data Migration

# Get cassandra container
$ docker ps | grep cassandra
$ docker exec -it ${cassandra_container} cqlsh
$ cqlsh> show version;
[cqlsh 5.0.1 | Cassandra 3.11.1 | CQL spec 3.4.4 | Native protocol v4]
$ cqlsh> USE $KEYSPACE_NAME;

Export

COPY $TABLE_NAME TO '$CSV_FILE_FULL_PATH'

Import

COPY $TABLE_NAME FROM '$CSV_FILE_FULL_PATH'

Debug

Log

Check logs through docker:

$ docker logs cassandra-example

Python driver

  • Install the driver: pip install cassandra-driver

References

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