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From "Phil Yang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17871) scan#setBatch(int) call leads wrong result of VerifyReplication
Date Wed, 05 Apr 2017 10:15:41 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15956624#comment-15956624
] 

Phil Yang commented on HBASE-17871:
-----------------------------------

It seems HBASE-15191 introduced this feature wrongly... We only setBatch in map() whose Scan
object is scanning peer table. I think we should also setBatch in createSubmittableJob whose
Scan object is scanning source table. As I said this feature is useful to prevent MR job OOM.
So I think we can add setBatch in createSubmittableJob? WDYT? Thanks.

> scan#setBatch(int) call leads wrong result of VerifyReplication
> ---------------------------------------------------------------
>
>                 Key: HBASE-17871
>                 URL: https://issues.apache.org/jira/browse/HBASE-17871
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 2.0.0, 1.4.0
>            Reporter: Tomu Tsuruhara
>            Assignee: Tomu Tsuruhara
>            Priority: Minor
>         Attachments: HBASE-17871.master.001.patch
>
>
> VerifyReplication tool printed weird logs.
> {noformat}
> 2017-04-03 23:30:50,252 ERROR [main] org.apache.hadoop.hbase.mapreduce.replication.VerifyReplication:
CONTENT_DIFFERENT_ROWS, rowkey=a00001001930000
> 2017-04-03 23:30:50,280 ERROR [main] org.apache.hadoop.hbase.mapreduce.replication.VerifyReplication:
ONLY_IN_PEER_TABLE_ROWS, rowkey=a00001001930000
> 2017-04-03 23:30:50,387 ERROR [main] org.apache.hadoop.hbase.mapreduce.replication.VerifyReplication:
CONTENT_DIFFERENT_ROWS, rowkey=a00001003850000
> 2017-04-03 23:30:50,414 ERROR [main] org.apache.hadoop.hbase.mapreduce.replication.VerifyReplication:
ONLY_IN_PEER_TABLE_ROWS, rowkey=a00001003850000
> 2017-04-03 23:30:50,480 ERROR [main] org.apache.hadoop.hbase.mapreduce.replication.VerifyReplication:
CONTENT_DIFFERENT_ROWS, rowkey=a00001005320000
> 2017-04-03 23:30:50,508 ERROR [main] org.apache.hadoop.hbase.mapreduce.replication.VerifyReplication:
ONLY_IN_PEER_TABLE_ROWS, rowkey=a00001005320000
> {noformat}
> Here, each bad rows were marked as both {{CONTENT_DIFFERENT_ROWS}} and {{ONLY_IN_PEER_TABLE_ROWS}}.
> This should never happen so I took a look at code and found scan.setBatch call.
> {code}
>     @Override
>     public void map(ImmutableBytesWritable row, final Result value,
>                     Context context)
>         throws IOException {
>       if (replicatedScanner == null) {
> 	    ...
>         final Scan scan = new Scan();
>         scan.setBatch(batch);
> {code}
> As stated in HBASE-16376, {{scan#setBatch(int)}} call implicitly allows scan results
to be partial.
> Since {{VerifyReplication}} is assuming each {{scanner.next()}} call returns entire row,
> partial results break compare logic.
> We should avoid setBatch call here.
> Thanks to RPC chunking (explained in this blog https://blogs.apache.org/hbase/entry/scan_improvements_in_hbase_1),
> it's safe and acceptable I think.



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