[KAFKA-16384] KRaft controller number recommendation

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 3.7.0
• Component/s: kraft
• Assignee: Unassigned
• Reporter: Peter
• Created: 19/Mar/24 03:46
• Updated: 19/Mar/24 23:02

Description

There seems to be some conflicting information about how many controllers should be used for a KRaft cluster. The first section listed mentions 3 or 5 controllers may be used, but the second section mentions no more than 3 should be used at the moment.

https://kafka.apache.org/documentation/#kraft_voter

> A Kafka admin will typically select 3 or 5 servers for this role, depending on factors like cost and the number of concurrent failures your system should withstand without availability impact. A majority of the controllers must be alive in order to maintain availability. With 3 controllers, the cluster can tolerate 1 controller failure; with 5 controllers, the cluster can tolerate 2 controller failures.

https://kafka.apache.org/documentation/#kraft_deployment

> For redundancy, a Kafka cluster should use 3 controllers. More than 3 controllers is not recommended in critical environments. In the rare case of a partial network failure it is possible for the cluster metadata quorum to become unavailable. This limitation will be addressed in a future release of Kafka.

 

Is 3 still the recommended number and is there more information on what the network issues are that could cause issues when using 5 controllers?