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Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Describe the problems you are trying to solve.

From Kafka documentation 

"By default, the SASL user name will be the primary part of the Kerberos principal. One can change that by
setting sasl.kerberos.principal.to.local.rules to a customized rule in server.properties. The format of
sasl.kerberos.principal.to.local.rules is a list where each rule works in the same way as
the auth_to_local in Kerberos configuration file (krb5.conf) (http://web.mit.edu/Kerberos/krb5-latest/doc/admin/conf_files/krb5_conf.html). 

Each rules starts with RULE: and contains an expression in the format [n:string](regexp)s/pattern/replacement/g."

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

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