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https://issues.apache.org/jira/browse/HDFS-12737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16222981#comment-16222981
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Kihwal Lee commented on HDFS-12737:
-----------------------------------
If the same user (i.e. the same UGI instance) talks to the same namenode via
RPC, a connection will be shared. If the files system cache is disabled, the
sharing cannot happen. Are those requests being made by separate processes?
> Thousands of sockets lingering in TIME_WAIT state due to frequent file open
> operations
> --------------------------------------------------------------------------------------
>
> Key: HDFS-12737
> URL: https://issues.apache.org/jira/browse/HDFS-12737
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ipc
> Environment: CDH5.10.2, HBase Multi-WAL=2, 250 replication peers
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
>
> On a HBase cluster we found HBase RegionServers have thousands of sockets in
> TIME_WAIT state. It depleted system resources and caused other services to
> fail.
> After months of troubleshooting, we found the issue is the cluster has
> hundreds of replication peers, and has multi-WAL = 2. That creates hundreds
> of replication threads in HBase RS, and each thread opens WAL file *every
> second*.
> We found that the IPC client closes socket right away, and does not reuse
> socket connection. Since each closed socket stays in TIME_WAIT state for 60
> seconds in Linux by default, that generates thousands of TIME_WAIT sockets.
> {code:title=ClientDatanodeProtocolTranslatorPB:createClientDatanodeProtocolProxy}
> // Since we're creating a new UserGroupInformation here, we know that no
> // future RPC proxies will be able to re-use the same connection. And
> // usages of this proxy tend to be one-off calls.
> //
> // This is a temporary fix: callers should really achieve this by using
> // RPC.stopProxy() on the resulting object, but this is currently not
> // working in trunk. See the discussion on HDFS-1965.
> Configuration confWithNoIpcIdle = new Configuration(conf);
> confWithNoIpcIdle.setInt(CommonConfigurationKeysPublic
> .IPC_CLIENT_CONNECTION_MAXIDLETIME_KEY, 0);
> {code}
> This piece of code is used in DistributedFileSystem#open()
> {noformat}
> 2017-10-27 14:01:44,152 DEBUG org.apache.hadoop.ipc.Client: New connection
> Thread[IPC Client (1838187805) connection to /172.131.21.48:20001 from
> blk_1013754707_14032,5,main] for remoteId /172.131.21.48:20001
> java.lang.Throwable: For logging stack trace, not a real exception
> at org.apache.hadoop.ipc.Client.getConnection(Client.java:1556)
> at org.apache.hadoop.ipc.Client.call(Client.java:1482)
> at org.apache.hadoop.ipc.Client.call(Client.java:1443)
> at
> org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:230)
> at com.sun.proxy.$Proxy28.getReplicaVisibleLength(Unknown Source)
> at
> org.apache.hadoop.hdfs.protocolPB.ClientDatanodeProtocolTranslatorPB.getReplicaVisibleLength(ClientDatanodeProtocolTranslatorPB.java:198)
> at
> org.apache.hadoop.hdfs.DFSInputStream.readBlockLength(DFSInputStream.java:365)
> at
> org.apache.hadoop.hdfs.DFSInputStream.fetchLocatedBlocksAndGetLastBlockLength(DFSInputStream.java:335)
> at
> org.apache.hadoop.hdfs.DFSInputStream.openInfo(DFSInputStream.java:271)
> at
> org.apache.hadoop.hdfs.DFSInputStream.<init>(DFSInputStream.java:263)
> at org.apache.hadoop.hdfs.DFSClient.open(DFSClient.java:1585)
> at
> org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:326)
> at
> org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:322)
> at
> org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
> at
> org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:322)
> at
> org.apache.hadoop.fs.FilterFileSystem.open(FilterFileSystem.java:162)
> at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:783)
> at
> org.apache.hadoop.hbase.wal.WALFactory.createReader(WALFactory.java:293)
> at
> org.apache.hadoop.hbase.wal.WALFactory.createReader(WALFactory.java:267)
> at
> org.apache.hadoop.hbase.wal.WALFactory.createReader(WALFactory.java:255)
> at
> org.apache.hadoop.hbase.wal.WALFactory.createReader(WALFactory.java:414)
> at
> org.apache.hadoop.hbase.replication.regionserver.ReplicationWALReaderManager.openReader(ReplicationWALReaderManager.java:70)
> at
> org.apache.hadoop.hbase.replication.regionserver.ReplicationSource$ReplicationSourceWorkerThread.openReader(ReplicationSource.java:747)
> at
> org.apache.hadoop.hbase.replication.regionserver.ReplicationSource$ReplicationSourceWorkerThread.run(ReplicationSource.java:543)
> {noformat}
> Unfortunately, given the HBase's usage pattern, this hack creates the problem.
> Ignoring the fact that having hundreds of HBase replication peers is a bad
> practice (I'll probably file a HBASE jira to help remedy that), the fact that
> Hadoop IPC client does not reuse socket seems not right. The relevant code is
> historical and deep in the stack, so I'd like to invite comments. I have a
> patch but it's pretty hacky.
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