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    Cassandra Nodes in the Junos Space Fabric Overview

    The Apache Cassandra service is implemented in Junos Space Network Management Platform Release 15.2R1 to provide a distributed file system to store device image files. Junos Space nodes that have the Cassandra service enabled and running are called Cassandra nodes and when two or more Cassandra nodes exist in a Junos Space fabric, they form the Cassandra cluster. A Cassandra cluster in Junos Space can have nodes running only the Cassandra service (dedicated Cassandra nodes) or JBoss nodes running the Cassandra service, or a combination of both. With the Cassandra service implemented, the device image files are moved from the MySQL database to the Cassandra cluster, thereby improving the performance of the MySQL database.

    In the Junos Space fabric, Cassandra clusters can have the following types of nodes:

    • JBoss nodes with the Cassandra service enabled

      A Cassandra cluster can be formed in a Junos Space fabric by enabling the Cassandra service on JBoss nodes existing in the fabric. When the Cassandra service is enabled on a JBoss node, the node acts as both a JBoss node and Cassandra node.

      Figure 1 shows a Cassandra cluster with the Cassandra service enabled on the existing JBoss nodes.

      Figure 1: Cassandra Service on JBoss Nodes

      Cassandra Service on
JBoss Nodes
    • Dedicated Cassandra nodes

      A dedicated Cassandra node provides only the Cassandra service in a fabric. If a dedicated Cassandra node already exists in the fabric, any new dedicated Cassandra node added to the fabric, together with the existing Cassandra node, forms a Cassandra cluster.

      Within a fabric, a Cassandra cluster can have any number of Cassandra nodes (that is, a fabric can contain a Cassandra cluster of up to eight Cassandra nodes).

      Figure 2 shows a Cassandra cluster with dedicated Cassandra nodes.

      Figure 2: Cassandra Service on Dedicated Cassandra Nodes

      Cassandra Service
on Dedicated Cassandra Nodes
    • Dedicated Cassandra nodes and JBoss nodes with the Cassandra service enabled

      A Cassandra cluster can comprise both dedicated Cassandra nodes and JBoss nodes on which the Cassandra service is enabled.

      Figure 3 shows a Cassandra cluster with a JBoss and Cassandra node and a dedicated Cassandra node.

      Figure 3: Cassandra Service on JBoss and Dedicated Cassandra Nodes

      Cassandra Service on
JBoss and Dedicated Cassandra Nodes

    For a JBoss node to provide the distributed file functionality, you must first enable and then start the Cassandra service. You can enable, disable, start, or stop the Cassandra service on a JBoss node from the Junos Space Platform GUI.

    Note: You cannot start the Cassandra service on dedicated database nodes or Fault Monitoring and Performance Monitoring (FMPM) nodes.

    You can also use the command-line interface of a JBoss node to monitor the Cassandra cluster in a fabric as follows:

    • To monitor the Cassandra cluster, use the nodetool status command.

      The nodetool utility lists all the nodes in the Cassandra cluster and their status as shown in the following sample:

      [user@host ~]# nodetool status platform
      Datacenter: DC1
      ===============
      Status=Up/Down
      |/ State=Normal/Leaving/Joining/Moving
      --  Address       Load       Tokens  Owns (effective)  Host ID                               Rack
      UN  192.0.2.120  75.39 KB   256     100.0%            844cf4c4-e6ad-498a-a85f-c841d1f72419  RAC1
      UN  192.0.2.121  84.94 KB   256     100.0%            d670b1b8-d2a4-41b0-badb-0fc61dc88a5c  RAC1
      
    • The Cassandra service provides the cqlsh command-line tool for interacting with the Cassandra database.

      You can connect to the Cassandra database from any JBoss node by using the cqlsh <ip address> -u <username> -p <password> command, where <ip address> is the IP address of the Cassandra node, <username> is the username and <password> is the password used to access the Cassandra node.

      [user@host]# cqlsh 192.0.2.120 -u test-user -p test-pwd
      Connected to Test Cluster at 192.0.2.120:9042
      [cqlsh 5.0.1 | Cassandra 2.1.2 | CQL spec 3.2.0 | Native protocol V3]
      Use HELP for help
      
      cqlsh>
      

    Release History Table

    Release
    Description
    The Apache Cassandra service is implemented in Junos Space Network Management Platform Release 15.2R1 to provide a distributed file system to store device image files.

    Modified: 2017-06-14