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Current state: Under Discussion

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread] 

JIRA: here

Motivation

Kafka connect currently supports running a single version of a connector. As the externals system that a connector supports evolves over time, the connectors may need to make incompatible changes between versions to keep up with new capabilities. Without the ability to run multiple versions of a connector, we would need to run the connectors in two different connect clusters if we want to support both version simultaneously. In addition, support for multiple connectors makes it possible to do two phase upgrades to connectors with the benefit of easier rollbacks. A connector runtime restart will still be required to install a newer version, however existing connectors can still continue to use the older version. The migration to the newer version is decoupled from the installation of the connector and will not require a cluster restart. The decoupling also makes rollbacks easier and will no longer require a cluster rollback. Finally, multiple version eases development toil while making changes to a connector. 

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