[infinispan-issues] [JBoss JIRA] (ISPN-8962) PreferAvailabilityStrategy: Rely less on the stable topology

[Dan Berindei (JIRA)]

Dan Berindei created ISPN-8962:
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             Summary: PreferAvailabilityStrategy: Rely less on the stable topology
                 Key: ISPN-8962
                 URL: https://issues.jboss.org/browse/ISPN-8962
             Project: Infinispan
          Issue Type: Bug
          Components: Core
    Affects Versions: 9.2.0.Final
            Reporter: Dan Berindei
            Assignee: Dan Berindei
             Fix For: 9.3.0.Final, 9.2.1.Final


{{PreferAvailabilityStrategy}} checks the size of the stable topology, and only considers cache topologies that are derived from the biggest topology (in size) when picking a post-merge topology.

Unfortunately, in some situations this algorithm fails pretty badly. If a node has a very long GC pause, when it comes back it will report the old topology *and* the old stable topology. If the rest of the cluster rebalanced, it now has both a smaller current topology and a smaller stable topology.

Furthermore, the stable topology is updated asynchronously, independent from the current topology. So even if there's a split and the minority partition installs a current topology with fewer members, it may take some time for its stable topology to be updated with fewer members. In fact, it appears that when a rebalance is not needed (e.g. because the partition has a single node), the stable topology is never updated!




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