[HDFS-16675] DatanodeAdminManager.stopDecommission fails with ConcurrentModificationException

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.2.1
• Component/s: namanode
• Assignee: Prabhu Joseph
• Reporter: Prabhu Joseph
• Created: 21/Jul/22 10:06
• Updated: 26/Jul/22 05:05

Description

DatanodeAdminManager.stopDecommission intermittently fails with ConcurrentModificationException.

java.util.ConcurrentModificationException: Tree has been modified outside of iterator
        at org.apache.hadoop.hdfs.util.FoldedTreeSet$TreeSetIterator.checkForModification(FoldedTreeSet.java:311)
        at org.apache.hadoop.hdfs.util.FoldedTreeSet$TreeSetIterator.hasNext(FoldedTreeSet.java:256)
        at org.apache.hadoop.hdfs.util.FoldedTreeSet$TreeSetIterator.next(FoldedTreeSet.java:262)
        at java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1044)
        at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.processExtraRedundancyBlocksOnInService(BlockManager.java:4300)
        at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeAdminManager.stopDecommission(DatanodeAdminManager.java:241)

This is intermittently seen on busy cluster with AutoScale Enabled. This leads to a Node with state "IN Service" in pendingNodes queue

2022-07-21 06:54:38,562 WARN org.apache.hadoop.hdfs.server.blockmanagement.DatanodeAdminManager (DatanodeAdminMonitor-0): DatanodeAdminMonitor caught exception when processing node 1.2.3.4:9866.
java.lang.IllegalStateException: Node 1.2.3.4:9866 is in an invalid state! Invalid state: In Service 0 blocks are on this dn.
        at com.google.common.base.Preconditions.checkState(Preconditions.java:172)
        at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeAdminManager$Monitor.check(DatanodeAdminManager.java:601)
        at org.apache.hadoop.hdfs.server.blockmanagement.DatanodeAdminManager$Monitor.run(DatanodeAdminManager.java:504)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
        at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:750)