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Part 9 BDC Cassandra dBDawood Sayyed/GLDS June 21st , 2016 Internal

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Few questions before we start

What is fixed schema and Dynamic schema?

What is SQL dB ?

What is NoSQL dB ?

Any advantages of No SQL dB over SQL dB ?

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SQL vs NoSQL

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Apache Cassandra

Apache Cassandra is a wide-column, open source most commonly used NoSQL database . The container of data, equivalent to a database schema in a relational database, in Apache Cassandra is a Keyspace.

The basic unit of storage is a column family (also called table), and each record in a table is stored in a row with the data being stored in columns. A column has a name, a value, and a timestamp associated with it. A column is not required to store a value and the column could be empty.

Apache Cassandra is based on a flexible schema (or schema-free or dynamic schema) data model in which different rows could have different columns and the columns are not required to be pre-specified in a table definition. Apache Cassandra supports data types for column names (called comparators) and column values (called validators), but does not require the data types (validators and comparators) to be specified.

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Apache Casandra

The validators and comparators may be added or modified after a table (column family) has been defined.

Apache Cassandra provides a Cassandra Query Language (CQL) for CRUD (add, get, update, delete)operations on a table.

Apache Cassandra installation includes a cqlsh utility, which is an interactive shell , from which CQL commands may be run.

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Graphical of Apache Cassandra

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Setting Environment for Apache Casandra

Starting Apache Cassandra

Starting the TTY

Connecting to CQL Shell

Creating a Keyspace

Altering A Keyspace

Using A Keyspace

Creating a Table

Adding Table Data

Querying a Table

Deleting from a Table

Truncating a Table

Dropping A Table

Dropping a Keyspace

Exiting CQLSh

Stopping Apache Cassandra

Starting Multiple Instances of Apache Cassandra

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Commands

sudo docker pull cassandra:latest

sudo docker images

docker run --name some-cassandra -d cassandra:tag

Start the Apache Cassandra server process in a Docker container with the following command in which the inter-node Apache Cassandra cluster communication port is specified as 7000 and the directory in which Apache Cassandra stores data is /cassandra/data. The container name is specified with the –name option as cassandradb

sudo docker run -t -i -v /cassandra/data:/var/lib/cassandra/data --name cassandradb -d –p 7000:7000 Cassandra

sudo docker ps

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Commands for TTY and connecting to CQL shell

sudo docker exec -it cassandradb bash

cqlsh

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Creating a Keyspace Apache Cassandra

A Keyspace is the container of application data and is used to group column families. Replication is set at a per-keyspace basis. The DDL command for creating a Keyspace is as follows.

CREATE KEYSPACE (IF NOT EXISTS)? <identifier> WITH <properties>

Case-insensitive and may consist exclusively of alpha-numeric characters with a maximum length of 32. To make a keyspace name case-sensitive add quotes.

The supported properties by the CREATE KEYSPACE statement, which creates a top-level keyspace, are replication for specifying the replication strategy and options and durable_writes for whether a commit log is to be used for updates on the keyspace, with the replication property being mandatory.

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Creating a Keyspace Apache Cassandra

CREATE KEYSPACE (IF NOT EXISTS)? <identifier> WITH <properties>

As an example, create a keyspace called CatalogKeyspace with replication strategy class as SimpleStrategy and replication factor as 3.

CREATE KEYSPACE CatalogKeyspace

WITH replication = {'class': 'SimpleStrategy', 'replication_factor' : 3};

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Stopping Apache Cassandra

To stop Apache Cassandra, stop the Docker container running the Apache Cassandra server.

sudo docker stop cassandradb

Subsequently, run the following command to list the running containers.

sudo docker ps

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Multiple Docker Containers for Instances of Apache Cassandra

sudo docker run -t -i -v /cassandra/data:/var/lib/cassandra/data --name cassandradb -d -p

7000:7000 Cassandra

sudo docker run -t -i -v /cassandra/data:/var/lib/cassandra/data --name cassandradb2 -d -p

7000:7000 Cassandra

sudo docker run -t -i -v /cassandra/data:/var/lib/cassandra/data --name cassandradb3 -d -p

7000:7000 -e CASSANDRA_SEEDS=52.91.214.50,54.86.243.122,54.86.205.95 Cassandra

Start a third container and specify the CASSANDRA_SEEDS environment variable for the IP address/es to be used to run multiple nodes in the cluster if required.