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From "Vinay (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-5177) blocksScheduled count should be decremented for abandoned blocks
Date Tue, 10 Sep 2013 05:46:55 GMT
Vinay created HDFS-5177:
---------------------------

             Summary: blocksScheduled  count should be decremented for abandoned blocks
                 Key: HDFS-5177
                 URL: https://issues.apache.org/jira/browse/HDFS-5177
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
    Affects Versions: 2.1.0-beta, 3.0.0
            Reporter: Vinay


DatanodeDescriptor#incBlocksScheduled() will be called for all datanodes of the block on each
allocation. But same should be decremented for abandoned blocks.

When one of the datanodes is down and same is allocated for the block along with other live
datanodes, then this block will be abandoned, but the scheduled count on other datanodes will
consider live datanodes as loaded, but in reality these datanodes may not be loaded.

Anyway this scheduled count will be rolled every 20 mins.

Problem will come if the rate of creation of files is more. Due to increase in the scheduled
count, there might be chances of missing local datanode to write to. and some times writes
also can fail in small clusters.

So we need to decrement the unnecessary count on abandon block call.

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