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https://issues.apache.org/jira/browse/HDFS-13671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16516463#comment-16516463
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Xiao Chen commented on HDFS-13671:
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Thanks all for the comments.
I reviewed HDFS-9260's benchmark and did some minidfscluster with 20k files
runs with and without HDFS-9260, which looks like:
||version||create files one-by-one||delete altogether||delete ops/sec||
|with|(189088+183722+182669) / 3 = 185159|(88 + 87 + 89) / 3 = 88|227k|
|without|(197381+194467+183217) / 3 = 191688|(131+104+101) / 3 = 112|178k|
Considering with a real production, the removal will be more scattered
resulting in more fragmentation / rebalancing, costing both cpu cycles and gc,
I think the 4x slower microbenchmark number isn't very exaggerated.
[~linyiqun], do you happen to know what 's the deletion rate in your cluster
before HDFS-9260? (I doubt if it's at 344k blocks/sec :) )
Given that there seems to be more interest and existing work on the old
implementation, reverting is fine by me. The reverting needs to be done
compatibly though, and it seems to be compatible as long as the new field in
{{DatanodeProtocol.proto}} is not removed.
> Namenode deletes large dir slowly caused by FoldedTreeSet#removeAndGet
> ----------------------------------------------------------------------
>
> Key: HDFS-13671
> URL: https://issues.apache.org/jira/browse/HDFS-13671
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 3.1.0, 3.0.3
> Reporter: Yiqun Lin
> Priority: Major
>
> NameNode hung when deleting large files/blocks. The stack info:
> {code}
> "IPC Server handler 4 on 8020" #87 daemon prio=5 os_prio=0
> tid=0x00007fb505b27800 nid=0x94c3 runnable [0x00007fa861361000]
> java.lang.Thread.State: RUNNABLE
> at
> org.apache.hadoop.hdfs.util.FoldedTreeSet.compare(FoldedTreeSet.java:474)
> at
> org.apache.hadoop.hdfs.util.FoldedTreeSet.removeAndGet(FoldedTreeSet.java:849)
> at
> org.apache.hadoop.hdfs.util.FoldedTreeSet.remove(FoldedTreeSet.java:911)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.DatanodeStorageInfo.removeBlock(DatanodeStorageInfo.java:252)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlocksMap.removeBlock(BlocksMap.java:194)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlocksMap.removeBlock(BlocksMap.java:108)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.removeBlockFromMap(BlockManager.java:3813)
> at
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.removeBlock(BlockManager.java:3617)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.removeBlocks(FSNamesystem.java:4270)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.deleteInternal(FSNamesystem.java:4244)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.deleteInt(FSNamesystem.java:4180)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.delete(FSNamesystem.java:4164)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.delete(NameNodeRpcServer.java:871)
> at
> org.apache.hadoop.hdfs.server.namenode.AuthorizationProviderProxyClientProtocol.delete(AuthorizationProviderProxyClientProtocol.java:311)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.delete(ClientNamenodeProtocolServerSideTranslatorPB.java:625)
> at
> org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:617)
> {code}
> In the current deletion logic in NameNode, there are mainly two steps:
> * Collect INodes and all blocks to be deleted, then delete INodes.
> * Remove blocks chunk by chunk in a loop.
> Actually the first step should be a more expensive operation and will takes
> more time. However, now we always see NN hangs during the remove block
> operation.
> Looking into this, we introduced a new structure {{FoldedTreeSet}} to have a
> better performance in dealing FBR/IBRs. But compared with early
> implementation in remove-block logic, {{FoldedTreeSet}} seems more slower
> since It will take additional time to balance tree node. When there are large
> block to be removed/deleted, it looks bad.
> For the get type operations in {{DatanodeStorageInfo}}, we only provide the
> {{getBlockIterator}} to return blocks iterator and no other get operation
> with specified block. Still we need to use {{FoldedTreeSet}} in
> {{DatanodeStorageInfo}}? As we know {{FoldedTreeSet}} is benefit for Get not
> Update. Maybe we can revert this to the early implementation.
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