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From "Andrey Gura (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IGNITE-2854) Need to implement deadlock detection
Date Fri, 01 Apr 2016 19:43:25 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-2854?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15222229#comment-15222229
] 

Andrey Gura commented on IGNITE-2854:
-------------------------------------

Algorithm described in previous comment has one drawback: it can't detect deadlock for transaction
that was timed out and involved into deadlock or can detect invalid deadlock due to a race
conditions. 

For example we have transactions {{TX1}} and {{TX2}} with the same timeout and start time.
{{TX1}} holds lock on key {{K1}} and requests lock for {{K2}} while {{TX2}} hold lock on key
{{K2}} and requests lock for {{K1}} so it is deadlcok. {{K1}} and {{K2}} have different primary
nodes so both transactions are distributed. 

When {{TX1}} and {{TX2}} times out all {{GridDhtColocatedLockFuture}} and blocked {{GridDhtLockFuture}}
times out also. {{GridDhtLockFuture.onTimeout}} initiates deadlock detection while {{GridDhtColocatedLockFuture.onTimeout}}
releases locks and then rollback corresponding transaction. So we have incomplete information
about transactions state.

> Need to implement deadlock detection
> ------------------------------------
>
>                 Key: IGNITE-2854
>                 URL: https://issues.apache.org/jira/browse/IGNITE-2854
>             Project: Ignite
>          Issue Type: New Feature
>          Components: cache
>    Affects Versions: 1.5.0.final
>            Reporter: Valentin Kulichenko
>            Assignee: Andrey Gura
>             Fix For: 1.6
>
>
> Currently, if transactional deadlock occurred, there is no easy way to find out which
locks were reordered.
> We need to add a mechanism that will collect information about awating candidates, analyze
it and show guilty keys. Most likely this should be implemented with the help of custom discovery
message.
> In addition we should automatically execute this mechanism if transaction times out and
add information to timeout exception.



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