Node in Apache Cassandra

In this article, we are going to discuss what is a node in Cassandra, information of node, how we can access the information about the node, and by using Nodetool utility we will also discuss some nodetool commands. let’s discuss one by one.

Node :

• A node in Cassandra contains the actual data and it’s information such that location, data center information, etc.
• A node contains the data such that keyspaces, tables, the schema of data, etc.
• you can perform operations such that read, write, delete data, etc. on a node.
• A node plays an important role in Cassandra clusters.
• In Cassandra ring where every node is connected peer to peer and every node is similar to every other node in the cluster.

Let’s consider an example where you have three replicas of data and each replica on different nodes. now, if you want to read data then anyone node can respond that’s why the concept of distributed data across the cluster is so effective and high availability mechanism in Cassandra.

Nodetool :

• It is the node management utility tool by which you can get the node health information, node information, cluster information, etc.
• with the help of nodetool commands, you can access all the required information of the nodes.
• Nodetool commands such that help, info, the status will give you the general information about the node.
• It’s by default located in the bin/ folder where Cassandra is installed.

Some basics Nodetool commands :

Command	Descriptions
help	It will list out all the nodetool commands.
status	It will give you the status and a reports about basic health information of the node.
info	It will give you the descriptions of the current settings and stats of the node.

Example –

nodetool status

let’s consider an example if a user wants to know the status of the node, then nodetool status commands need to be executed. In given below output is showing node is in the UN (Up and Normal) state and the address of a default node is 127.0.0.1 and also about load and rack information, etc.

 C:\Program Files\apache-cassandra-3.11.4\bin>nodetool status
Datacenter: datacenter1
========================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address    Load       Tokens       Owns    Host ID                               Rack
UN  127.0.0.1  322.11 KiB  256          ?       83ae1bed-37b7-46c0-a166-2a774e147205  rack1 

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