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Vinayakumar B commented on HDFS-10453: -------------------------------------- In Branch-2 code, {{BlockManager#computeReconstructionWorkForBlocks()}}, flow goes like below before reaching the part of the code where you have provided the patch, 1. With global-lock held, {{work}} list will be created with the blocks which are exactly present at that time in {{scheduleReplication()}}, lock will be released after creating the list. {code} if (block.isDeleted() || !block.isCompleteOrCommitted()) { // remove from neededReplications neededReplications.remove(block, priority); return null; }{code} 2. For blocks in {{work}} list, targets will be chosen. 3. Global lock will be acquired again, recheck happens for all {{ReplicationWork}} blocks which have got targets, whether block deleted or not during step #2. Now only blocks which are not deleted during this time will be proceeded for replication. {code} if (block.isDeleted() || !block.isCompleteOrCommitted()) { neededReplications.remove(block, priority); rw.resetTargets(); return false; }{code} Therefore the problem you mentioned in the description does not occur IMO. Correct me, If I am wrong. > ReplicationMonitor thread could stuck for long time due to the race between > replication and delete of same file in a large cluster. > ----------------------------------------------------------------------------------------------------------------------------------- > > Key: HDFS-10453 > URL: https://issues.apache.org/jira/browse/HDFS-10453 > Project: Hadoop HDFS > Issue Type: Bug > Components: namenode > Affects Versions: 2.4.1, 2.7.1 > Reporter: He Xiaoqiao > Attachments: HDFS-10453-branch-2.001.patch, > HDFS-10453-branch-2.003.patch, HDFS-10453.001.patch > > > ReplicationMonitor thread could stuck for long time and loss data with little > probability. Consider the typical scenarioļ¼ > (1) create and close a file with the default replicas(3); > (2) increase replication (to 10) of the file. > (3) delete the file while ReplicationMonitor is scheduling blocks belong to > that file for replications. > if ReplicationMonitor stuck reappeared, NameNode will print log as: > {code:xml} > 2016-04-19 10:20:48,083 WARN > org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy: Failed to > place enough replicas, still in need of 7 to reach 10 > (unavailableStorages=[], storagePolicy=BlockStoragePolicy{HOT:7, > storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]}, > newBlock=false) For more information, please enable DEBUG log level on > org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy > ...... > 2016-04-19 10:21:17,184 WARN > org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy: Failed to > place enough replicas, still in need of 7 to reach 10 > (unavailableStorages=[DISK], storagePolicy=BlockStoragePolicy{HOT:7, > storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]}, > newBlock=false) For more information, please enable DEBUG log level on > org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy > 2016-04-19 10:21:17,184 WARN > org.apache.hadoop.hdfs.protocol.BlockStoragePolicy: Failed to place enough > replicas: expected size is 7 but only 0 storage types can be selected > (replication=10, selected=[], unavailable=[DISK, ARCHIVE], removed=[DISK, > DISK, DISK, DISK, DISK, DISK, DISK], policy=BlockStoragePolicy{HOT:7, > storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]}) > 2016-04-19 10:21:17,184 WARN > org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy: Failed to > place enough replicas, still in need of 7 to reach 10 > (unavailableStorages=[DISK, ARCHIVE], storagePolicy=BlockStoragePolicy{HOT:7, > storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]}, > newBlock=false) All required storage types are unavailable: > unavailableStorages=[DISK, ARCHIVE], storagePolicy=BlockStoragePolicy{HOT:7, > storageTypes=[DISK], creationFallbacks=[], replicationFallbacks=[ARCHIVE]} > {code} > This is because 2 threads (#NameNodeRpcServer and #ReplicationMonitor) > process same block at the same moment. > (1) ReplicationMonitor#computeReplicationWorkForBlocks get blocks to > replicate and leave the global lock. > (2) FSNamesystem#delete invoked to delete blocks then clear the reference in > blocksmap, needReplications, etc. the block's NumBytes will set > NO_ACK(Long.MAX_VALUE) which is used to indicate that the block deletion does > not need explicit ACK from the node. > (3) ReplicationMonitor#computeReplicationWorkForBlocks continue to > chooseTargets for the same blocks and no node will be selected after traverse > whole cluster because no node choice satisfy the goodness criteria > (remaining spaces achieve required size Long.MAX_VALUE). > During of stage#3 ReplicationMonitor stuck for long time, especial in a large > cluster. invalidateBlocks & neededReplications continues to grow and no > consumes. it will loss data at the worst. > This can mostly be avoided by skip chooseTarget for BlockCommand.NO_ACK block > and remove it from neededReplications. -- This message was sent by Atlassian JIRA (v6.3.4#6332) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org