[infinispan-issues] [JBoss JIRA] (ISPN-6107) State transfer should not fetch segments that were added during a rebalance

[Dan Berindei (JIRA)]

Dan Berindei created ISPN-6107:
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             Summary: State transfer should not fetch segments that were added during a rebalance
                 Key: ISPN-6107
                 URL: https://issues.jboss.org/browse/ISPN-6107
             Project: Infinispan
          Issue Type: Bug
          Components: Core, Test Suite - Core
    Affects Versions: 8.1.0.Final
            Reporter: Dan Berindei
            Assignee: Dan Berindei
             Fix For: 8.2.0.Beta1


When the last owner of a segment leaves the cache, the coordinator will update the consistent hash and replace that owner with {{numOwners}} owners (so that a segment always has at least 1 owner). If there is a rebalance in progress, it could be that both the current and the pending CH lost all the owners of a segment, and the coordinator will assign new owners in both CHs (not necessarily the same).

Sometimes, this causes tests that create clusters with many nodes to spend a lot of time shutting down the cluster. Here's an example:

# Cluster ABCDE, coordinator A, topology id = 0, currentCH = \{0: CD, 1: BC\}, pendingCH = null
# D leaves
# A broadcasts a REBALANCE_START command with topology id 1, members = ABCE, currentCH = \{0: C, 1: BC\}, pendingCH = \{0: BC, 1: BC\}
# A and E confirm that they finished the rebalance
# C leaves before sending the data for segment 0 to B
# A broadcasts a CH_UPDATE command with topology id 2, members = ABE, currentCH = \{0: AE, 1: B\}, pendingCH = \{0: B, 1: B\}
# A now owns segment 0 in the writeCH (which is the union of currentCH and pendingCH).
# A tries to request segment 0 from the other owner in the currentCH, E
# B confirms that it finished the rebalance
# A broadcasts a new topology: topology id 3, currentCH = \{0: B, 1: B\}, pendingCH = null
# E installs topology 3, and throws an IllegalArgumentException when handling A's request for segments
# A is not able to install topology 3, because it requests the transactions data while holding the lock on the LocalCacheStatus
# A receives the IllegalArgumentException from E and retries. But because it still has the old topology, it retries on E ad infinitum - using a lot of CPU in the process.

A requesting segment 0 from E is not a problem in itself - normally E would just send back an empty set of transactions and entries. The problem is that the cluster is able to install a new topology, because A already confirmed receiving all the data, but A is stuck with the old topology.



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