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Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?

None

• If we are changing behavior how will we phase out the older behavior?

Existing mechanisms will continue to be supported. The new mechanisms can be enabled in the broker along with SASL/GSSAPI and SASL/PLAIN. Existing upgrade procedures for new SASL mechanisms (as currently described in the documentation) can be used to switch to SCRAM.

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Specify username, password as Kafka client properties instead of the JAAS configuration configuration 

JAAS configuration is the standard Java way of specifying security properties and since Kafka already relies on JAAS configuration for SASL, it makes sense to store the options in jaas.conf. This is also consistent with SASL/PLAIN implementation in Kafka and similar mechanisms in Zookeeper. However, JAAS configuration is not particularly flexible  and hence providing credentials as properties may provide an interface that is simpler to use. But this should be looked at in the context of all SASL mechanisms rather than just SCRAM.

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