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The KafkaChannel and ExpiringCredentialRefreshingLogin classes can easily retrieve this the ClientChannelCredentialTracker instance and tell it when various events of interest occur (a channel is initially authenticated, a credential is refreshed, a channel is closed).  The events are enqueued as they are reported, and a background thread processes them to decide which KafkaChannel instances need to re-authenticate.

Compatibility, Deprecation, and Migration Plan

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