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From "jiraposter@reviews.apache.org (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4485) Eliminate window of missing Data
Date Fri, 21 Oct 2011 15:18:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4485?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13132740#comment-13132740
] 

jiraposter@reviews.apache.org commented on HBASE-4485:
------------------------------------------------------



bq.  On 2011-10-21 06:13:51, Lars Hofhansl wrote:
bq.  > src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java, line 216
bq.  > <https://reviews.apache.org/r/2481/diff/1/?file=51678#file51678line216>
bq.  >
bq.  >     I'm not usually a fan of instanceof - unless necessary of course.
bq.  >     Why did you need to fold this into one loop?

The reason for having one loop is because we want to get the
Scanners for the storefiles and the scanners for memstore at
the same time. This is required for ensuring that the view of
the StoreScanner is consistent with the state of the store,
at some point in the execution history.

I agree, instance of is kinda ugly. Will try to get rid of that.


- Amitanand


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This is an automatically generated e-mail. To reply, visit:
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On 2011-10-20 19:13:56, Amitanand Aiyer wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/2481/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2011-10-20 19:13:56)
bq.  
bq.  
bq.  Review request for Ted Yu, Michael Stack, Jonathan Gray, Lars Hofhansl, Amitanand Aiyer,
Kannan Muthukkaruppan, Karthik Ranganathan, and Nicolas Spiegelberg.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  Part of the 2856 diff split into 3 parts for easier review
bq.  
bq.  The first part is v6 of the patch submitted to:
bq.  https://reviews.apache.org/r/2224/
bq.  
bq.  This is the fix for HBase-4485
bq.  
bq.  
bq.  This addresses bug hbase-4485.
bq.      https://issues.apache.org/jira/browse/hbase-4485
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    src/main/java/org/apache/hadoop/hbase/regionserver/Store.java 7761c42 
bq.    src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java f5b5c4c 
bq.    src/main/java/org/apache/hadoop/hbase/regionserver/MemStore.java 34263e4 
bq.  
bq.  Diff: https://reviews.apache.org/r/2481/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  running mvn test with all 3 patches together.
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Amitanand
bq.  
bq.


                
> Eliminate window of missing Data
> --------------------------------
>
>                 Key: HBASE-4485
>                 URL: https://issues.apache.org/jira/browse/HBASE-4485
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Amitanand Aiyer
>            Assignee: Amitanand Aiyer
>             Fix For: 0.94.0
>
>         Attachments: 4485-v1.diff, 4485-v2.diff, 4485-v3.diff, 4485-v4.diff, repro_bug-4485.diff
>
>
> After incorporating v11 of the 2856 fix, we discovered that we are still having some
ACID violations.
> This time, however, the problem is not about including "newer" updates; but, about missing
older updates
> that should be including. 
> Here is what seems to be happening.
> There is a race condition in the StoreScanner.getScanners()
>   private List<KeyValueScanner> getScanners(Scan scan,
>       final NavigableSet<byte[]> columns) throws IOException {
>     // First the store file scanners
>     List<StoreFileScanner> sfScanners = StoreFileScanner
>       .getScannersForStoreFiles(store.getStorefiles(), cacheBlocks,
>                                 isGet, false);
>     List<KeyValueScanner> scanners =
>       new ArrayList<KeyValueScanner>(sfScanners.size()+1);
>     // include only those scan files which pass all filters
>     for (StoreFileScanner sfs : sfScanners) {
>       if (sfs.shouldSeek(scan, columns)) {
>         scanners.add(sfs);
>       }
>     }
>     // Then the memstore scanners
>     if (this.store.memstore.shouldSeek(scan)) {
>       scanners.addAll(this.store.memstore.getScanners());
>     }
>     return scanners;
>   }
> If for example there is a call to Store.updateStorefiles() that happens between
> the store.getStorefiles() and this.store.memstore.getScanners(); then
> it is possible that there was a new HFile created, that is not seen by the
> StoreScanner, and the data is not present in the Memstore.snapshot either.

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