[infinispan-issues] [JBoss JIRA] (ISPN-3244) TopologyAwareSyncConsistentHashFactory should limit the number of segments per node

[Dan Berindei (JIRA)]

Dan Berindei created ISPN-3244:
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             Summary: TopologyAwareSyncConsistentHashFactory should limit the number of segments per node
                 Key: ISPN-3244
                 URL: https://issues.jboss.org/browse/ISPN-3244
             Project: Infinispan
          Issue Type: Bug
          Components: State transfer
    Affects Versions: 5.3.0.CR2, 5.2.6.Final
            Reporter: Dan Berindei
            Assignee: Dan Berindei
             Fix For: 5.3.0.Final


Let's say we have a cluster with 5 nodes: A(r1), B(r2), C(r2), D(r3), E(r3)

TopologyAwareConsistentSyncHashFactory will spread the segments equally on each rack, meaning A will own 2x segments compared to the other nodes.

TopologyAwareConsistentHashFactory limits the maximum number per node, so that A owns just as many segments as the other nodes. With a slight limitation: the number of racks must be greater than numOwners, otherwise each rack must hold (at least) one copy of all the data.

TopologyAwareConsistentSyncHashFactory is a little random, so we can't distribute the data perfectly, but we can limit the number of segments on each node to something like 1.5x the average number of segments.

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