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From "Igor Seliverstov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (IGNITE-8841) MVCC TX: Read transactions remap when coordinator fails.
Date Fri, 01 Feb 2019 12:14:00 GMT

    [ https://issues.apache.org/jira/browse/IGNITE-8841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16758247#comment-16758247
] 

Igor Seliverstov commented on IGNITE-8841:
------------------------------------------

I split the initial task into two parts - 
1) turning the transaction into a read query (done in scope of this ticket)
2) allowing writes using newly acquired version (IGNITE-11173)

[~rkondakov],[~Pavlukhin], [~amashenkov], [~vozerov], the first part is ready for review.
Should I rewrite the ticket description according on made changes?

> MVCC TX: Read transactions remap when coordinator fails.
> --------------------------------------------------------
>
>                 Key: IGNITE-8841
>                 URL: https://issues.apache.org/jira/browse/IGNITE-8841
>             Project: Ignite
>          Issue Type: Bug
>          Components: mvcc, sql
>            Reporter: Roman Kondakov
>            Assignee: Igor Seliverstov
>            Priority: Major
>              Labels: failover
>          Time Spent: 50m
>  Remaining Estimate: 0h
>
> At the moment read transactions that don't acquire topology lock will be forcibly rolled
back on topology change as read tx can be in fly while topology being change.
>  This is done to prevent having active transaction with stale snapshots on new topology
in cases of TX coordinator or Near node were lost.
>  
> It would be nice to remap it somehow until they locked a topology or at least throw some
meaningful exception to user.
>  For example, it is possible to obtain a new "write" mvcc version from the new coordinator
and use this version for all further writes while using "old" version for reads. In this case
we need to change visibility rules a little: "old" version should see "own" updates made
by "new" "write" version.



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