Replicas

The Replicas metric group contains metrics regarding the state of replicas in the cluster. The metrics available are:

  • ISR Expand Rate
  • ISR Shrink Rate
  • Under Min ISR Partitions
  • Under Replicated Partitions

ISR Expand Rate

The ISR Expand Rate metric displays the number of increases of In-Sync Replicas (ISR) per second, averaged over the past minute. ISR expansions occur when a broker comes online, such as when recovering from a failure or adding a new node. This increases the number of in-sync replicas available for each partition on that broker.

Expected value: 0

ISR Shrink Rate

The ISR Shrink Rate metric displays the number of decreases of In-Sync Replicas (ISR) per second, averaged over the past minute. ISR shrinks occur when an in-sync broker goes down, as it decreases the number of in-sync replicas available for each partition replica on that broker.

Expected value: 0

Under Min ISR Partitions

The Under Min ISR Partitions metric displays the number of partitions, where the number of In-Sync Replicas (ISR) is less than the minimum number of in-sync replicas specified. The two most common causes of under-min ISR partitions are that one or more brokers is unresponsive, or the cluster is experiencing performance issues and one or more brokers are falling behind.

Expected value: 0

A graph of the number of ISR partitions under the minimum on an Apache Kafka cluster.

Under Replicated Partitions

The Under Replicated Partitions metric displays the number of partitions that do not have enough replicas to meet the desired replication factor. A partition will also be considered under-replicated if the correct number of replicas exist, but one or more of the replicas have fallen significantly behind the partition leader. The two most common causes of under-replicated partitions are that one or more brokers is unresponsive, or the cluster is experiencing performance issues and one or more brokers have fallen behind.

Expected value: 0

A graph of the number of under replicated partitions on an Apache Kafka cluster.

By Instaclustr Support
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