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An additional server-side metric expired-connections-killed-total will be created to count the number of such events.  It should remain at zero if all clients and brokers are upgraded to v2.1.0 or later.  If it is non-zero then either an older client is connecting (which would be evidenced in the tagged auth=v0 metric mentioned above) or a newer client is not re-authenticating correctly (which would indicate a bug).

A clientClient-side metric will metrics reauthentication-latency-ms-{avg,max} will be created that documents document the latency imposed by re-authentication.  It is unclear if this latency will be problematic, and the data collected via this metric these metrics may be useful as we consider this issue in the future.

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