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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