Status

Current state: "Under Discussion"Accepted

Vote thread: Re: [VOTE} KIP-733: change Kafka Streams default replication factor config (there is no DISCUSS thread)Discussion thread: TODO

JIRA:

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Since Kafka 2.4.0, it is possible to rely on the broker default replication factor setting when creating a topic (cf KIP-464: Defaults for AdminClient#createTopic). Even if approved via KIP-464 already, Kafka Streams did not adapt this new feature yet, due to backward compatibility concern. However, it puts some burden on users to change the Kafka Streams default replication.factor config of 1 when concerns. Given the upcoming major release, we want to enable this feature in Kafka Streams by default now. The main motivation is, that the current default replication.factor=1  puts some burden on users to change the config when they put an application into production. While user are already able to change the config to -1  if their brokers are on 2.4.0 or newer version, it's still an additional config they need to take care of.

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We propose the change the default value of StreamsConfig.REPLICATION_FACTOR_CONFIG from 1 to -1 (meaning use broker default). We also change the "importance level" of replication.factor from HIGH to MEDIUM.

Compatibility, Deprecation, and Migration Plan

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Note: if an existing application is upgrade, users won't be affected, because if internal replication/changleog topics exist already, no create topic request would be sent anyway. Only if a new application is deployed, or if an existing application is reset, and thus repartition/changelog topics would need to be created users might be affected. Because the application won't startup for this case, the impact is minor and can be considered non-critical. Applications already running in production won't break.

We also believe that 2.3.0 broker a sufficiently old such that not too many user may be affected, and we It is unclear how many users might be affected because they use older brokers than 2.4.0. However, we consider it an important improvement for default configs and want to take to opportunity of a major release to make this change (as it's technically breaking backward compatibility).

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