[jira] [Resolved] (HBASE-28595) Losing exception from scan RPC can lead to partial results

["Duo Zhang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-28595?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Duo Zhang resolved HBASE-28595.
-------------------------------
    Fix Version/s: 2.4.18
                   2.7.0
                   3.0.0-beta-2
                   2.6.1
                   2.5.9
     Hadoop Flags: Reviewed
       Resolution: Fixed

Pushed to all active branches.

Thanks [~csringhofer] for contributing and all others for helping and reviewing!

> Losing exception from scan RPC can lead to partial results
> ----------------------------------------------------------
>
>                 Key: HBASE-28595
>                 URL: https://issues.apache.org/jira/browse/HBASE-28595
>             Project: HBase
>          Issue Type: Bug
>          Components: Client, regionserver, Scanners
>            Reporter: Csaba Ringhofer
>            Assignee: Csaba Ringhofer
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 2.4.18, 2.7.0, 3.0.0-beta-2, 2.6.1, 2.5.9
>
>
> This was discovered in Apache Impala using HBase 2.2 based branch hbase client and server. It is not clear yet whether other branches are also affected.
> The issue happens if the server side of the scan throws an exception and closes the scanner, but at the same time, the client gets an rpc connection closed error and doesn't process the exception sent by the server. Client then thinks it got a network error, which leads to retrying the RPC instead of opening a new scanner. But then when the client retry reaches the server, the server returns an empty ScanResponse instead of an error, leading to closing the scanner on client side without returning any error.
> A few pointers to critical parts:
> region server:
> 1st call throws exception leading to closing (but not deleting) scanner:
> [https://github.com/apache/hbase/blob/0c8607a35008b7dca15e9daaec41ec362d159d67/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RSRpcServices.java#L3539]
> 2nd call (retry of 1st) returns empty results:
> [https://github.com/apache/hbase/blob/0c8607a35008b7dca15e9daaec41ec362d159d67/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RSRpcServices.java#L3403]
> client:
> some exceptions are handled as non-retriable at RPC level and are only handled through opening a new scanner:
> [https://github.com/apache/hbase/blob/0c8607a35008b7dca15e9daaec41ec362d159d67/hbase-client/src/main/java/org/apache/hadoop/hbase/client/ScannerCallable.java#L214]
> [https://github.com/apache/hbase/blob/0c8607a35008b7dca15e9daaec41ec362d159d67/hbase-client/src/main/java/org/apache/hadoop/hbase/client/ClientScanner.java#L367]
> This mechanism in the client only works if it gets the exception from the server. If there are connection issues during the RPC then the client won't really know the state of the server.



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