[jira] [Created] (KAFKA-14426) Add documentation for Kraft limtations that have open KIPs

["Greg Harris (Jira)" <ji...@apache.org>]

Greg Harris created KAFKA-14426:
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             Summary: Add documentation for Kraft limtations that have open KIPs
                 Key: KAFKA-14426
                 URL: https://issues.apache.org/jira/browse/KAFKA-14426
             Project: Kafka
          Issue Type: Task
          Components: documentation, kraft
            Reporter: Greg Harris


Currently there are a number of limitations for Kraft, which are described as the motivation for the following open KIPs:
* [https://cwiki.apache.org/confluence/display/KAFKA/KIP-853%3A+KRaft+Voter+Changes]
* [https://cwiki.apache.org/confluence/display/KAFKA/KIP-856%3A+KRaft+Disk+Failure+Recovery]
* [https://cwiki.apache.org/confluence/display/KAFKA/KIP-650%3A+Enhance+Kafkaesque+Raft+semantics#KIP650:EnhanceKafkaesqueRaftsemantics-Pre-vote] 

These limitations are:
* No online method of resizing the controller quorum
* No online method of recovering from controller disk loss
* No support for heterogeneous voter lists in running controller nodes
* When using a quorum size 3, there is no live-upgrade roll which is tolerant of a single unplanned machine failure.
* When using a quorum size >3, there is a risk of non-linearizable reads.

These are significant enough concerns for operations of a Kraft-enabled cluster that they should be documented as official limitations in the ops documentation.

Optionally, we may wish to provide or link to more detailed operations documentation about performing the offline-resize or offline-recovery stages, in addition to describing that such offline procedures are necessary.



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