AWS : Cassandra on a Single-Node Cluster

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Apache Cassandra is a highly scalable NoSQL database system usually running on multi-nodes setup.

It is a free and open-source distributed database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure.

Cassandra offers robust support for clusters spanning multiple datacenters, with asynchronous masterless replication allowing low latency operations for all clients. - wiki

Here is the summary for the characteristics of Apache Cassandra:

One of the most popular structured storage DBMS.
Uses a hybrid key-value / wide column architecture.
Originally created Facebook, now open-source.
Cross-platform support written in Java.
Supports massively distributed environments.
Highly scalable and decentralized : all nodes (servers) have the same role which means no single point of failure.
Automatic data replication : highly fault tolerant which means individual node can fail without downtime.
Supports MapReduce.
Used by CERN, Digg, Instagram, Netflix, Reddit, Walmart, Twitter, etc.
In Cassandra, related data for an application are stored in a container known as a keyspace which contains one or more column families.

In this tutorial, we'll learn how to install and use on a single-node cluster on Ubuntu 14.04.

Cassandra requires that the Java SE Runtime Environment (JRE) be installed: Cassandra 3.0+ requires the most stable version of Java 8.

$ java -version
openjdk version "1.8.0_91"
OpenJDK Runtime Environment (build 1.8.0_91-8u91-b14-0ubuntu4~14.04-b14)
OpenJDK 64-Bit Server VM (build 25.91-b14, mixed mode)

Install Cassandra

$ echo "deb http://www.apache.org/dist/cassandra/debian 35x main" | sudo tee -a /etc/apt/sources.list.d/cassandra.sources.list
$ echo "deb-src http://www.apache.org/dist/cassandra/debian 35x main" | sudo tee -a /etc/apt/sources.list.d/cassandra.sources.list

We need to add three public keys from the Apache Software Foundation:

$ sudo gpg --keyserver pgp.mit.edu --recv-keys F758CE318D77295D
$ sudo gpg --export --armor F758CE318D77295D | sudo apt-key add -

$ sudo gpg --keyserver pgp.mit.edu --recv-keys 2B5C1B00
$ sudo gpg --export --armor 2B5C1B00 | sudo apt-key add -

$ sudo gpg --keyserver pgp.mit.edu --recv-keys 0353B12C
$ sudo gpg --export --armor 0353B12C | sudo apt-key add -

Update the package:

$ sudo apt-get update

Now we want to install Cassandra:

$ sudo apt-get install cassandra

We may have a connection issue. So, we should replace <public name> with 127.0.0.1 in /etc/cassandra/cassandra-env.sh:

JVM_OPTS="$JVM_OPTS -Djava.rmi.server.hostname=127.0.0.1"

Run Cassandra

Cassandra should have been started automatically when it's installed, however, it does not. Seems there is a bug.

To confirm that it's not running, type:

$ sudo service cassandra status
 * could not access pidfile for Cassandra

To start:

$ sudo /etc/init.d/cassandra start

$ sudo service cassandra status
 * Cassandra is running

Installation created the following directories.

/var/lib/cassandra (data directories)
/var/log/cassandra (log directory)
/var/run/cassandra (runtime files)
/usr/share/cassandra (environment settings)
/usr/share/cassandra/lib (JAR files)
/usr/bin (binary files)
/usr/sbin
/etc/cassandra (configuration files)
/etc/init.d (service startup script)
/etc/security/limits.d (cassandra user limits)
/etc/default

Cqlsh

Start cqlsh using the command cqlsh as shown below.

It gives the Cassandra cqlsh prompt as output:

Connected to Test Cluster at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 3.5 | CQL spec 3.4.0 | Native protocol v4]
Use HELP for help.
cqlsh>

We may get the following connection error:

$ cqlsh
Connection error: ('Unable to connect to any servers', {'127.0.0.1': error(111, "Tried connecting to [('127.0.0.1', 9042)]. Last error: Connection refused")})

To fix the issue, we need to define environment variable CQLSH_NO_BUNDLED and export it:

$ sudo pip install cassandra-driver
$ export CQLSH_NO_BUNDLED=true

We installed the latest Python Cassandra driver and tell cqlsh (which is Python program) to use the external Cassandra Python driver, not the one bundled with the distribution.