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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12737) Thousands of sockets lingering in TIME_WAIT state due to frequent file open operations
Date Tue, 14 Nov 2017 01:22:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16250627#comment-16250627

Todd Lipcon commented on HDFS-12737:

Not following what you mean by "implement multiplexing in the future" -- it's already the
case that we share a single connection from multiple proxies so long as the UGI matches, isn't
it? The ipc.Client class has a Map<ConnectionId, Connection> and the UGI makes up part
of the ConnectionId. So simply using a non-block-token-based UGI and then passing the token
as a call parameter ought to be sufficient to share a single connection.

> 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
> {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 / from blk_1013754707_14032,5,main] for
remoteId /
> 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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