[infinispan-issues] [JBoss JIRA] (ISPN-3422) In non-tx caches, write operations may not be atomic during rebalance

[Dan Berindei (JIRA)]

Dan Berindei created ISPN-3422:
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             Summary: In non-tx caches, write operations may not be atomic during rebalance
                 Key: ISPN-3422
                 URL: https://issues.jboss.org/browse/ISPN-3422
             Project: Infinispan
          Issue Type: Bug
            Reporter: Dan Berindei
            Assignee: Dan Berindei


If the cache topology changes while a write command is running and before it has actually committed the entry to the data container, we retry the command (see ISPN-3366 and ISPN-3357). But before we detect the topology change, one or more of the backup owners may have already applied the modification.

Retrying the command re-acquires the key lock on the primary owner (even if the primary owner didn't change). That means another command could have modified the same key in the meantime, but the retried command is going to ignore any changes and is going to return the value before the first attempt. Obviously, the command is not retried if the first attempt is not successful, but scenarios like this are possible:

{code}
thread 1: putIfAbsent(k, v1) -> null
thread 2: putIfAbsent(k, v2) -> null
{code}

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