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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11295) Long running scan produces OutOfOrderScannerNextException
Date Wed, 04 Jun 2014 22:57:02 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14018302#comment-14018302
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Anoop Sam John commented on HBASE-11295:
----------------------------------------

When the first request for a scan is executed in HRS the next seq id expected (from client)
is the incremented one ie. 1 
Yes the out of order exp is a DNRIOE.   The normal retry is from client on client timeout.

In this case of timeout we should not allow that retry to happen. The first try is already
in progress and the scan advanced some rk levels. The retry will skip those snd we will fail
getting those rows.
On the out of order exception no retry ( like u see before) has to happen. It will be cloding
that scanner and creating a new scanner.   U mean this new is not happening? This way it was
when we wrote code need to see any change made later fir not happen.

> Long running scan produces OutOfOrderScannerNextException
> ---------------------------------------------------------
>
>                 Key: HBASE-11295
>                 URL: https://issues.apache.org/jira/browse/HBASE-11295
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 0.96.0
>            Reporter: Jeff Cunningham
>         Attachments: OutOfOrderScannerNextException.tar.gz
>
>
> Attached Files:
> HRegionServer.java - instramented from 0.96.1.1-cdh5.0.0
> HBaseLeaseTimeoutIT.java - reproducing JUnit 4 test
> WaitFilter.java - Scan filter (extends FilterBase) that overrides filterRowKey() to sleep
during invocation
> SpliceFilter.proto - Protobuf defintiion for WaitFilter.java
> OutOfOrderScann_InstramentedServer.log - instramented server log
> Steps.txt - this note
> Set up:
> In HBaseLeaseTimeoutIT, create a scan, set the given filter (which sleeps in overridden
filterRowKey() method) and set it on the scan, and scan the table.
> This is done in test client_0x0_server_150000x10().
> Here's what I'm seeing (see also attached log):
> A new request comes into server (ID 1940798815214593802 - RpcServer.handler=96) and a
RegionScanner is created for it, cached by ID, immediately looked up again and cached RegionScannerHolder's
nextCallSeq incremeted (now at 1).
> The RegionScan thread goes to sleep in WaitFilter#filterRowKey().
> A short (variable) period later, another request comes into the server (ID 8946109289649235722
- RpcServer.handler=98) and the same series of events happen to this request.
> At this point both RegionScanner threads are sleeping in WaitFilter.filterRowKey(). After
another period, the client retries another scan request which thinks its next_call_seq is
0.  However, HRegionServer's cached RegionScannerHolder thinks the matching RegionScanner's
nextCallSeq should be 1.



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