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https://issues.apache.org/jira/browse/HBASE-2283?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12845657#action_12845657
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Kannan Muthukkaruppan commented on HBASE-2283:
----------------------------------------------
Stack:
btw, I think there might be preexisting issue with timestamps & WAL stuff for
deletes that come in with LATEST timestamp. Could you check the code and
confirm?
Basically, in:
{code}
delete(byte [] family, List<KeyValue> kvs, boolean writeToWAL)
{code}
the "kv.updateLatestStamp(byteNow);" time stamp massaging happens *after* the
WAL log.append() call. So the keyvalues written to the HLog does not have the
massaged timestamp. On recovery, when these entries are replayed, we add them
back to reconstructionCache but don't do anything with timestamps.
> row level atomicity
> --------------------
>
> Key: HBASE-2283
> URL: https://issues.apache.org/jira/browse/HBASE-2283
> Project: Hadoop HBase
> Issue Type: Bug
> Reporter: Kannan Muthukkaruppan
> Priority: Blocker
> Fix For: 0.20.4, 0.21.0
>
> Attachments: rowLevelAtomicity_2283_v1.patch
>
>
> The flow during a HRegionServer.put() seems to be the following. [For now,
> let's just consider single row Put containing edits to multiple column
> families/columns.]
> HRegionServer.put() does a:
> HRegion.put();
> syncWal() (the HDFS sync call). /* this is assuming we have HDFS-200
> */
> HRegion.put() does a:
> for each column family
> {
> HLog.append(all edits to the colum family);
> write all edits to Memstore;
> }
> HLog.append() does a :
> foreach edit in a single column family {
> doWrite()
> }
> doWrite() does a:
> this.writer.append().
> There seems to be two related issues here that could result in
> inconsistencies.
> Issue #1: A put() does a bunch of HLog.append() calls. These in turn do a
> bunch of "write" calls on the underlying DFS stream. If we crash after
> having written out some append's to DFS, recovery will run and apply a
> partial transaction to memstore.
> Issue #2: The updates to memstore should happen after the sync rather than
> before. Otherwise, there is the danger that the write to DFS (sync) fails for
> some reason & we return an error to the client, but we have already taken
> edits to the memstore. So subsequent reads will serve uncommitted data.
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