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From "Perry Trolard (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-10179) HRegionServer underreports readRequestCounts by 1 under certain conditions
Date Mon, 16 Dec 2013 19:56:07 GMT
Perry Trolard created HBASE-10179:

             Summary: HRegionServer underreports readRequestCounts by 1 under certain conditions
                 Key: HBASE-10179
                 URL: https://issues.apache.org/jira/browse/HBASE-10179
             Project: HBase
          Issue Type: Bug
          Components: metrics
    Affects Versions: 0.94.6, 0.99.0
            Reporter: Perry Trolard
            Priority: Minor

In HRegionServer.scan(), if

 (a) the number of results returned, n, is greater than zero
 (b) but less than the size of the batch (nbRows)
 (c) and the size in bytes is smaller than the max size (maxScannerResultSize)

then the readRequestCount will be reported as n - 1 rather than n. (This is because the for-loop
counter i is used to update the readRequestCount, and if the scan runs out of rows before
reaching max rows or size, the code `break`s out of the loop and i is not incremented for
the final time.)

To reproduce, create a test table and open its details page in the web UI. Insert a single
row, then note the current request count, c. Scan the table, returning 1 row; the request
count will still be c, whereas it should be c + 1.

I have a patch against TRUNK I can submit. At Splice Machine we're running 0.94, & I'd
be happy to submit a patch against that as well. 

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