[jira] [Created] (BOOKKEEPER-799) Distribution schedule coverage sets don't take gaps in response lists into account when writequorum > ackquorum

["Ivan Kelly (JIRA)" <ji...@apache.org>]

Ivan Kelly created BOOKKEEPER-799:
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             Summary: Distribution schedule coverage sets don't take gaps in response lists into account when writequorum > ackquorum
                 Key: BOOKKEEPER-799
                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-799
             Project: Bookkeeper
          Issue Type: Bug
            Reporter: Ivan Kelly
            Assignee: Ivan Kelly
            Priority: Blocker
             Fix For: 4.4.0, 4.2.4


The algorithm now be used to check if all quorums are being covered when sending a read lac or fencing message is broken when writeQuorum >= ackQuorum.

The purpose of the algorithm is to tell us when we have heard a response from enough nodes, that an ack quorum could not possibly have been formed without at least one of the nodes that we have heard responses from.

The current algorithm works when writeQuorum == ackQuorum, as we consider all quorums covered if the first |ackQuorum| nodes in the writeQuorum are covered. However, this doesn't work in the case that it's the middle node in the quorum that we have heard.

Take the example, e:4, w:3, a:2, and we've heard from node 0, and node 2. In this case, it is possible for the write quorum, 1,2,3 to get an ack quorum if 1 and 3 response. 




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