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Cassandra.md

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Objective

To install Cassandra and test it on losalamos.

What's Cassandra

An open-source distributed-database management system for handling large amounts of data across many commodity servers with no single point of failure. Cassandra offers capabilities that relational databases and other NoSQL databases simply cannot match such as: continuous availability, linear scale performance, operational simplicity and easy data distribution across multiple data centers and cloud availability zones. The DataStax community has a lot of support for Cassandra, and we followed the steps and tutorials available on their website.

Steps for Installation:

  1. Check the java version and see that the machine has at least Java 7/8.
java -version
  1. Add Datastax community repository to the sources list file:
echo "deb http://debian.datastax.com/community stable main" | sudo tee -a /etc/apt/sources.list.d/cassandra.sources.list
  1. Add the Datastax repository key to the aptitude trusted keys:
curl -L http://debian.datastax.com/debian/repo_key | sudo apt-key add -
  1. Java Native Access (JNA) is required for production installations (latest version recommended). refer to : Installing the JNA on Debian or Ubuntu Systems
sudo apt-get install libjna-java
  1. Install Cassandra:
sudo apt-get update
sudo apt-get install dsc20=2.0.11-1 cassandra=2.0.11
  1. As the system starts the Cassandra service automatically, the server needs to be stopped and data must be cleared:
sudo service cassandra stop
sudo rm -rf /var/lib/cassandra/data/system/*
  1. Open port for Cassandra in iptables:
sudo iptable -A INPUT -p tcp --dport XXXX -j ACCEPT
  • XXXX is the port number of Cassandra, refer this

Steps for testing:

In Cassandra, a keyspace is a container for your application data. It is similar to the schema in a relational database.

  1. To start Cassandra:
sudo service cassandra start
  1. In command line, enter:
cqlsh
  1. Create Keyspace:
CREATE KEYSPACE demo
WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };

  1. Now we should be able to write the program and run oour code using Cassandra. For testing this out, we use the [tutorial] (https://academy.datastax.com/demos/getting-started-apache-cassandra-and-java-part-i). The tutorial also has a link to the java code which you can use. Remember to first create the User table, otherwise java program with throws exception.

  2. You can also use the cqlsh shell to create all the tables and test it on command line. An excellent tutorial is available here.

  3. The true power of Cassandra can be observed when you set it up on a multi-node cluster. For details, you can check how to initialize a multiple node cluster with single or multiple data centers.

#Another way to install Cassandra

  1. You first need to make sure the version of java on your machine is at least jdk7, jdk8 is the best. Otherwise you can not start cassandra.

  2. Download cassandra from the website http://cassandra.apache.org/download/, and decompress the file.

  3. Configure files. Find the configuration file cassandra/conf/cassandra.yaml, and add these values:

    data_file_directories:

    • /var/lib/cassandra/data

    commitlog_directory: /var/lib/cassandra/commitlog

    saved_caches_directory: /var/lib/cassandra/saved_caches

    Attention: You have to add these key-values in exactly the same format as above, or there will be an exception when you start cassandra. There is a space between key and value

  4. Create these directories:

sudo mkdir -p /var/lib/cassandra/data
sudo mkdir -p /var/lib/cassandra/saved_caches
sudo mkdir -p /var/lib/cassandra/commitlog
sudo mkdir -p /var/log/cassandra/
  1. Change the property of these directories:
sudo chown -R root:root /var/lib/cassandra
sudo chown -R root:root /var/log/cassandra/

Attention: "root:root" should be the user that you are logging in your system. Here I use root

  1. Configure the environment variables, open the file /etc/environment and add the environment variable:CASSANDRA_HOME=The address of your cassandra.

  2. Make your environment variables effective by executing the command:. /etc/environment

  3. Start your cassandra. Enter the bin file of your cassandra and execute the command:./cassandra -f

    Attention: If you see an exception like local_host:7000 port number is in use of another process, change the storage
    port number to 8000 or 9000.

  4. Access cassandra by typing in command:./cqlsh. Then you can use the instructions above to create your own tables.