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https://issues.apache.org/jira/browse/HDFS-7592?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Haohui Mai updated HDFS-7592:
-----------------------------
Resolution: Cannot Reproduce
Status: Resolved (was: Patch Available)
This is no longer an issue as BlockUnderConstruction has become a feature class
after the merge of EC branch.
> A bug in BlocksMap that cause NameNode memory leak.
> -----------------------------------------------------
>
> Key: HDFS-7592
> URL: https://issues.apache.org/jira/browse/HDFS-7592
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 0.21.0
> Environment: HDFS-0.21.0
> Reporter: JichengSong
> Assignee: JichengSong
> Labels: BB2015-05-TBR, BlocksMap, leak, memory
> Attachments: HDFS-7592.patch
>
>
> In our HDFS production environment, NameNode FGC frequently after running for
> 2 months, we have to restart NameNode manually.
> We dumped NameNode's Heap for objects statistics.
> Before restarting NameNode:
> num #instances #bytes class name
> ----------------------------------------------
> 1: 59262275 3613989480 [Ljava.lang.Object;
> ...
> 10: 8549361 615553992
> org.apache.hadoop.hdfs.server.namenode.BlockInfoUnderConstruction
> 11: 5941511 427788792
> org.apache.hadoop.hdfs.server.namenode.INodeFileUnderConstruction
> After restarting NameNode:
> num #instances #bytes class name
> ----------------------------------------------
> 1: 44188391 2934099616 [Ljava.lang.Object;
> ...
> 23: 721763 51966936
> org.apache.hadoop.hdfs.server.namenode.BlockInfoUnderConstruction
> 24: 620028 44642016
> org.apache.hadoop.hdfs.server.namenode.INodeFileUnderConstruction
> We find the number of BlockInfoUnderConstruction is abnormally large before
> restarting NameNode.
> As we know, BlockInfoUnderConstruction keeps block state when the file is
> being written. But the write pressure of
> our cluster is far less than million/sec. We think there is a memory leak in
> NameNode.
> We fixed the bug as followsing patch.
> diff --git
> a/hdfs/src/java/org/apache/hadoop/hdfs/server/namenode/BlocksMap.java
> b/hdfs/src/java/org/apache/hadoop/hdfs/server/namenode/BlocksMap.java
> index 7a40522..857d340 100644
> --- a/hdfs/src/java/org/apache/hadoop/hdfs/server/namenode/BlocksMap.java
> +++ b/hdfs/src/java/org/apache/hadoop/hdfs/server/namenode/BlocksMap.java
> @@ -205,6 +205,8 @@ class BlocksMap {
> DatanodeDescriptor dn = currentBlock.getDatanode(idx);
> dn.replaceBlock(currentBlock, newBlock);
> }
> + // change to fix bug about memory leak of NameNode
> + map.remove(newBlock);
> // replace block in the map itself
> map.put(newBlock, newBlock);
> return newBlock;
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