[jira] [Created] (HDFS-9958) BlockManager#createLocatedBlocks can throw NPE for corruptBlocks on failed storages.

["Kuhu Shukla (JIRA)" <ji...@apache.org>]

Kuhu Shukla created HDFS-9958:
---------------------------------

             Summary: BlockManager#createLocatedBlocks can throw NPE for corruptBlocks on failed storages.
                 Key: HDFS-9958
                 URL: https://issues.apache.org/jira/browse/HDFS-9958
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 2.7.2
            Reporter: Kuhu Shukla
            Assignee: Kuhu Shukla


In a scenario where the corrupt replica is on a failed storage, before it is taken out of blocksMap, there is a race which causes the creation of LocatedBlock on a {{machines}} array element that is not populated. 

Following is the root cause,
{code}
final int numCorruptNodes = countNodes(blk).corruptReplicas();
{code}
countNodes only looks at nodes with storage state as NORMAL, which in the case where corrupt replica is on failed storage will amount to numCorruptNodes being zero. 
{code}
final int numNodes = blocksMap.numNodes(blk);
{code}
However, numNodes will count all nodes/storages irrespective of the state of the storage. Therefore numMachines will include such (failed) nodes. The assert would fail only if the system is enabled to catch Assertion errors, otherwise it goes ahead and tries to create LocatedBlock object for that is not put in the {{machines}} array.

Here is the stack trace:
{code}
java.lang.NullPointerException
	at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo.toDatanodeInfos(DatanodeStorageInfo.java:45)
	at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo.toDatanodeInfos(DatanodeStorageInfo.java:40)
	at org.apache.hadoop.hdfs.protocol.LocatedBlock.<init>(LocatedBlock.java:84)
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlock(BlockManager.java:878)
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlock(BlockManager.java:826)
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlockList(BlockManager.java:799)
	at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.createLocatedBlocks(BlockManager.java:899)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocationsInt(FSNamesystem.java:1849)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocations(FSNamesystem.java:1799)
	at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getBlockLocations(FSNamesystem.java:1712)
	at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.getBlockLocations(NameNodeRpcServer.java:588)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.getBlockLocations(ClientNamenodeProtocolServerSideTranslatorPB.java:365)
	at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:616)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:982)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2049)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2045)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:415)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2043)
{code}



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