HBase: Introduction and Installation.

HBase is a column-oriented database management system that runs on top of Hadoop Distributed File System (HDFS). It is well suited for sparse data sets, which are common in many big data use cases. 

Unlike relational database systems, HBase does not support a structured query language like SQL; in fact, HBase isn’t a relational data store at all. HBase applications are written in Java much like a typical Apache MapReduce application. HBase does support writing applications in Apache  Avro, REST, and Thrift.

An HBase system comprises a set of tables. Each table contains rows and columns, much like a traditional database. Each table must have an element defined as a Primary Key, and all access attempts to HBase tables must use this Primary Key.

Avro, as a component, supports a rich set of primitive data types including: numeric, binary data and strings; and a number of complex types including arrays, maps, enumerations and records. A sort order can also be defined for the data.

Architecture:

In HBase, tables are split into regions and are served by the region servers. Regions are vertically divided by column families into “Stores”.The term ‘store’ is used for regions to explain the storage structure. Stores are saved as files in HDFS. Shown below is the architecture of HBase.

HBase has three major components: 

1. Client library 

2. Master server

3. Region servers 

Regions:

Regions are nothing but tables that are split up and spread across the region servers.

MasterServer :

• It Assigns regions to the region servers and takes the help of Apache ZooKeeper for this task.
• Handles load balancing of the regions across region servers. It unloads the busy servers and shifts the regions to less occupied servers.
• Maintains the state of the cluster by negotiating the load balancing.
• Is responsible for schema changes and other metadata operations such as creation of tables and column families.

Region Server:

The region servers have regions that -

• Communicate with the client and handle data-related operations.
• Handle read and write requests for all the regions under it.
• Decide the size of the region by following the region size thresholds.

ZooKeeper:

ZooKeeper is a high-performance coordination service for distributed applications(like HBase). It exposes common services like naming, configuration management, synchronization, and group services, in a simple interface so you don't have to write them from scratch. You can use it off-the-shelf to implement consensus, group management, leader election, and presence protocols. And you can build on it for your own, specific needs.

HBase relies completely on Zookeeper. HBase provides you the option to use its built-in Zookeeper which will get started whenever you start HBAse. But it is not good if you are working on a production cluster. In such scenarios it's always good to have a dedicated Zookeeper cluster and integrate it with your HBase cluster.

Installation:

Pre-requisites :

• Hadoop should be installed on your ubuntu OS. If not, install it from here

Step 1: Download the Hbase from http://www-eu.apache.org/dist/hbase/1.4.2/

Step 2: Open Terminal and login to the user you have created while installing hadoop. I have named hduser so i will login as 

           su - hduser

Step 3: Start Hadoop.

           start-dfs.sh
                start-yarn.sh

Step 4: Copy the downloaded hbase file to hduser folder

    sudo cp /home/tanmay/Downloads/hbase/hbase-1.4.1-bin.tar.gz  /home/hduser/

             Extract the file 

        tar -xvzf hbase-1.4.1-bin.tar.gz

Step 5: We will move this folder to usr/local and create a new folder named hbase.

       sudo mv hbase-1.4.1 /usr/local/hbase

Step 6: Edit ./bashrc

      sudo gedit ~/.bashrc 

Go to end and copy these lines

export HBASE_HOME=/usr/local/hbase
export PATH=$PATH:$HBASE_HOME/bin

Step 7: Edit the hosts file

            sudo gedit /etc/hosts

     

edit the second IP and type 127.0.0.1 

Step 8: We have to edit hbase-env.sh which is located in conf folder

         cd /usr/local/hbase/conf/

            sudo gedit hbase-env.sh

We give the java path in this hbase-env.sh

copy  export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64

Step 9 : Similarly we edit hbase-site.xml

           sudo gedit hbase-site.xml

Copy the following lines

<property>
<name>hbase.rootdir</name>
<value>hdfs://localhost:9000/hbase</value>
</property>

<property>
<name>hbase.master.port</name>
<value>60001</value>
</property>

<property>
<name>hbase.cluster.distributed</name>
<value>true</value>
</property>

<property>
<name>hbase.zookeeper.property.dataDir</name>
<value>/usr/local/zookeeper</value>
</property>

<property>
<name>hbase.zookeeper.property.maxClientCnxns</name>
<value>35</value>
</property>

Paste it in "Configuration".

Step 10: Finally we start Hbase.

           cd ..

              cd bin/

              ./start-hbase.sh

Step 11: To check whether hbase is installed properly we type

                        jps

If all the above nodes are displayed then your HBase is installed Perfectly.

Step 12: For gui display open browser and type localhost:16010