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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-18055) HBASE-17917 closes the scanners while a scan is in progess for switching over to stream reads
Date Tue, 16 May 2017 06:23:04 GMT
ramkrishna.s.vasudevan created HBASE-18055:
----------------------------------------------

             Summary: HBASE-17917 closes the scanners while a scan is in progess for switching
over to stream reads
                 Key: HBASE-18055
                 URL: https://issues.apache.org/jira/browse/HBASE-18055
             Project: HBase
          Issue Type: Bug
          Components: regionserver, Scanners
    Affects Versions: 2.0.0
            Reporter: ramkrishna.s.vasudevan
            Assignee: ramkrishna.s.vasudevan
             Fix For: 2.0.0


In HBASE-17917 tries to switch from pread to stream read when a specific size of bytes are
read. So in order to switch over, it closes the existing scanners and creates a new scanners
with pread=false.
When we close the exisitng scanners - if the blocks are served from offheap cache we will
decrement the ref count on those blocks and if it becomes zero we make the block ready for
eviction. Then there is a chance that the result could be corrupted if new blocks occupy the
cache. So the expectation was that till the RPC call completes the response we will hold on
to the blocks that are referred by the scan. (except the last one). So trying to switch over
to stream read will break this expectation and hence TestBlockEvictionfromclient fails. 



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