[ https://issues.jboss.org/browse/ISPN-4137?page=com.atlassian.jira.plugin.... ] Dan Berindei commented on ISPN-4137: ------------------------------------ While trying to write a test for the issue, I realized that the issue isn't actually related to state transfer. The only link with state transfer is that it may be more likely for a commit command to time out if it's waiting for a node to install a new topology, or forwarding the commit to a new node which is itself waiting for a new topology. Let's say we have a transaction with a put(k, v) command, the originator is A, and the key owners are B (primary) and C (backup). Let's also assume the local commit on either node can't fail, the only possible failure is replication timeout. If the commit command sent from A to C times out, A will send a rollback command to B and C, and there are two cases: 1. C applies the commit before receiving the rollback command, and writes {{k=v}} in the cache without B holding the lock on {{k}} - allowing it to overwrite another transaction. 2. C receives the rollback command and skips the commit command, leaving {{k=v}} on B and {{k=null}} on C. The only way out of this is to not send the rollback command at all, and use recovery to force the commit or rollback on A - but blocking any transactions that want to write to {{k}} in the meantime. When recovery is enabled, this is what my fix does, but I'm not sure if holding the lock on {{k}} for in-doubt transactions is ok. [~mircea.markus], WDYT? There is a slightly different problem that my PR does fix: if the commit succeeds on both B and C, but A sees a topology change, it will re-send the commit command to both B and C. Without the change, B and C will both replay both the prepare and the commit, allowing for inconsistencies. But with the change, the transaction is seen as already completed and B and C do nothing. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira