[jira] [Created] (HDFS-15495) Decommissioning a DataNode with corrupted EC files should not be blocked indefinitely

["Siyao Meng (Jira)" <ji...@apache.org>]

Siyao Meng created HDFS-15495:
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             Summary: Decommissioning a DataNode with corrupted EC files should not be blocked indefinitely
                 Key: HDFS-15495
                 URL: https://issues.apache.org/jira/browse/HDFS-15495
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: block placement, ec
    Affects Versions: 3.0.0
            Reporter: Siyao Meng
            Assignee: Siyao Meng


Originally discovered in patched CDH 6.2.1 (with a bunch of EC fixes: HDFS-14699, HDFS-14849, HDFS-14847, HDFS-14920, HDFS-14768, HDFS-14946, HDFS-15186).

When there's an EC file marked as corrupted on NN, if the admin tries to decommission a DataNode having one of the remaining blocks of the corrupted EC file, *the decom will never finish* unless the file is recovered by putting the missing blocks back in:

{code:title=The endless DatanodeAdminManager check loop, every 30s}
2020-07-23 16:36:12,805 TRACE blockmanagement.DatanodeAdminManager: Processed 0 blocks so far this tick
2020-07-23 16:36:12,806 DEBUG blockmanagement.DatanodeAdminManager: Processing Decommission In Progress node 127.0.1.7:5007
2020-07-23 16:36:12,806 TRACE blockmanagement.DatanodeAdminManager: Block blk_-9223372036854775728_1013 numExpected=9, numLive=4
2020-07-23 16:36:12,806 INFO BlockStateChange: Block: blk_-9223372036854775728_1013, Expected Replicas: 9, live replicas: 4, corrupt replicas: 0, decommissioned replicas: 0, decommissioning replicas: 1, maintenance replicas: 0, live entering maintenance replicas: 0, excess replicas: 0, Is Open File: false, Datanodes having this block: 127.0.1.12:5012 127.0.1.10:5010 127.0.1.8:5008 127.0.1.11:5011 127.0.1.7:5007 , Current Datanode: 127.0.1.7:5007, Is current datanode decommissioning: true, Is current datanode entering maintenance: false
2020-07-23 16:36:12,806 DEBUG blockmanagement.DatanodeAdminManager: Node 127.0.1.7:5007 still has 1 blocks to replicate before it is a candidate to finish Decommission In Progress.
2020-07-23 16:36:12,806 INFO blockmanagement.DatanodeAdminManager: Checked 1 blocks and 1 nodes this tick
{code}

"Corrupted" file here meaning the EC file doesn't have enough EC blocks in the block group to be reconstructed. e.g. for {{RS-6-3-1024k}}, when there are less than 6 blocks for an EC file, the file can no longer be retrieved correctly.

Will check on trunk as well soon.



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