Monitoring

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Monitoring

Monitoring means to monitor or monitoring generally means to be aware of the state of a system.

Cassandra exposes a number of statistics and management operations via Java Management Extensions (JMX). Java Management Extensions (JMX) is a Java technology that supplies tools for managing and monitoring Java applications and services. Any statistic or operation that a Java application has exposed as an MBean can then be monitored or manipulated using JMX.

During normal operation, Cassandra outputs information and statistics that you can monitor using JMX-compliant tools such as JConsole, the Cassandra nodetool utility, or the DataStax OpsCenter management console. With the same tools, you can perform certain administrative commands and operations such as flushing caches or doing a repair.

Monitoring Using nodetool
The nodetool utility is a command-line interface for monitoring Cassandra and performing routine database operations. It is included in the Cassandra distribution and is typically run directly from an operational Cassandra node.

The nodetool utility supports the most important JMX metrics and operations, and includes other useful commands for Cassandra administration. This utility is commonly used to output a quick summary of the ring and its current state of general health with the ring command. For example:

# nodetool -h localhost -p 7199 ring
Address        Status   State   Load        Owns    Range                                      Ring
95315431979199388464207182617231204396
10.194.171.160 Down     Normal  ?           39.98   61078635599166706937511052402724559481     |<–|
10.196.14.48   Up       Normal  3.16 KB     30.01   78197033789183047700859117509977881938     |   |
10.196.14.239  Up       Normal  3.16 KB     30.01   95315431979199388464207182617231204396     |–>|

The nodetool utility provides commands for viewing detailed metrics for column family metrics, server metrics, and compaction statistics. Commands are also available for important operations such as decommissioning a node, running repair, and moving partitioning tokens.