[jira] [Updated] (HBASE-12751) Allow RowLock to be reader writer

["Josh Elser (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-12751?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Josh Elser updated HBASE-12751:
-------------------------------
    Release Note: 
Locks on row are now reader/writer rather than exclusive.

Moves sequenceid out of HRegion and into MVCC class; MVCC is now in charge. A WAL append is still stamped in same way (we pass MVCC context in a few places where we previously we did not).

MVCC methods cleaned up. Make a bit more sense now. Less of them.

Simplifies our update of MemStore/WAL. Now we update memstore AFTER we add to WAL (but before we sync). This fixes possible dataloss when two edits came in with same coordinates; we could order the edits in memstore differently to how they arrived in the WAL.

Marked as an incompatible change because it breaks Distributed Log Replay, a feature we'd determined already was unreliable and to be removed.

  was:
Locks on row are now reader/writer rather than exclusive.

Moves sequenceid out of HRegion and into MVCC class; MVCC is now in charge. A WAL append is still stamped in same way (we pass MVCC context in a few places where we previously we did not).

MVCC methods cleaned up. Make a bit more sense now. Less of them.

Simplifies our update of MemStore/WAL. Now we update memstore AFTER we add to WAL (but before we sync). This fixes possible dataloss when two edits came in with same coordinates; we could order the edits in memstore differently to how they arrived in the WAL.

Marked as an incompatible change because it breaks Distributed Log Replay, a feature we'd determined already was unreliable and to be removed (See http://search-hadoop.com/m/YGbbhTJpoal8GD1).


> Allow RowLock to be reader writer
> ---------------------------------
>
>                 Key: HBASE-12751
>                 URL: https://issues.apache.org/jira/browse/HBASE-12751
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 1.3.0, 2.0.0
>            Reporter: Elliott Neil Clark
>            Assignee: Michael Stack
>            Priority: Major
>             Fix For: 2.0.0
>
>         Attachments: 12751.rebased.v25.txt, 12751.rebased.v26.txt, 12751.rebased.v26.txt, 12751.rebased.v27.txt, 12751.rebased.v29.txt, 12751.rebased.v31.txt, 12751.rebased.v32.txt, 12751.rebased.v32.txt, 12751.rebased.v33.txt, 12751.rebased.v34.txt, 12751.rebased.v35.txt, 12751.rebased.v35.txt, 12751.rebased.v35.txt, 12751.v37.txt, 12751.v38.txt, 12751.v39.txt, 12751.v40.txt, 12751.v41.txt, 12751v22.txt, 12751v23.txt, 12751v23.txt, 12751v23.txt, 12751v23.txt, 12751v36.txt, HBASE-12751-v1.patch, HBASE-12751-v10.patch, HBASE-12751-v10.patch, HBASE-12751-v11.patch, HBASE-12751-v12.patch, HBASE-12751-v13.patch, HBASE-12751-v14.patch, HBASE-12751-v15.patch, HBASE-12751-v16.patch, HBASE-12751-v17.patch, HBASE-12751-v18.patch, HBASE-12751-v19 (1).patch, HBASE-12751-v19.patch, HBASE-12751-v2.patch, HBASE-12751-v20.patch, HBASE-12751-v20.patch, HBASE-12751-v21.patch, HBASE-12751-v3.patch, HBASE-12751-v4.patch, HBASE-12751-v5.patch, HBASE-12751-v6.patch, HBASE-12751-v7.patch, HBASE-12751-v8.patch, HBASE-12751-v9.patch, HBASE-12751.patch
>
>
> Right now every write operation grabs a row lock. This is to prevent values from changing during a read modify write operation (increment or check and put). However it limits parallelism in several different scenarios.
> If there are several puts to the same row but different columns or stores then this is very limiting.
> If there are puts to the same column then mvcc number should ensure a consistent ordering. So locking is not needed.
> However locking for check and put or increment is still needed.



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