Static group membership

As explained in Kafka Streams in Action, Second Edition

Static membership is a Kafka consumer-group membership mode that assigns each consumer a persistent identity so it can rejoin with its previous partition assignment without an immediate rebalance.

Static membership gives each Kafka consumer a unique group.instance.id. The controller remembers that identity and can restore the consumer’s previous partition assignment when it rejoins, avoiding an immediate rebalance. section 4.3.4

Use static membership when consumers disappear temporarily and return soon:

• During rolling upgrades, stopping and restarting each consumer does not automatically trigger a rebalance for every instance. section 4.3.4
• When a consumer leaves, it does not send a leave group request; on rejoining, its unique membership ID lets the controller recover the original assignment. section 4.3.4
• Set session.timeout.ms high enough to cover expected transient unavailability, but low enough to detect genuine failures and trigger a rebalance. section 4.3.4

Figure 4.16 Static members don’t issue leave group requests when dropping out of a group, and a static ID allows the controller to remember them.

The membership flow shows how static IDs let the controller remember consumers that temporarily drop out without issuing leave group requests. section 4.3.4

How Kafka Streams in Action, Second Edition covers it

How deep it goes

Explains identity-based assignment recovery, timeout configuration, and the rebalance tradeoff without implementation code.

Examples

Uses rolling application upgrades and cloud nodes that temporarily disappear before returning online.

What it assumes

Assumes familiarity with Kafka consumers, consumer groups, partitions, assignments, and rebalancing.

What you can do after

Operate/configure consumers with unique group.instance.id values and a deliberately chosen session.timeout.ms.

How it connects

Connects consumer groups with partition assignment, rebalancing, cooperative rebalancing, and session timeouts.

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Related concepts

• consumer group rebalancingaddresses · Consumer group rebalancing is the redistribution of topic-partition assignments among consumer group members after membership or partition availability changes.
• group coordinatorimplemented by · A group coordinator is the Kafka broker responsible for managing a consumer group’s membership, liveness, partition assignments, and committed offsets.
• StatefulSetuses · A StatefulSet is a Kubernetes workload resource that manages stateful Pods with stable identities, ordered operations, and persistent storage associations.
• consumer groupused by · A consumer group is a logical set of message consumers that cooperatively processes a shared stream by distributing its partitions among group members.

This explainer was generated by Manning's knowledge graph from the text of Kafka Streams in Action, Second Edition. The section links point to the parts of the book it draws on.