如以上流程所示，当DFSClient create一个文件的时候，通过rpc call Namenode 的createFile来创建文件。Namenode调用FSNameSystem的startFile()， FSNameSystem又调用 LeaseManager 的addLease（）为新创建的文件添加一个lease。如果该lease已经存在，则update lease的lastUpdate 时间，并将该文件的path加入到lease中。然后，DFSClient 将通过调用DFSClient的put(),该文件的path put掉DFSClient中的 LeaseChecker中，（如果是第一次put，将会启动LeaseChecker这个守护线程）。这个过程是一个同步调用的过程。

文件create成功之后，守护线程LeaseChecker会每30s, 通过rpc调用renew一下 该DFSClient所拥有的lease。

文件的close（）与create（）是个完全不同的过程。close（）主要完成了2个操作。

1. LeaseChecker的close（）会将pendingCreates 列表中的全部项remove掉，并将文件路径对应的OutputStream全部close

2. interrupt() LeaseChecker 线程

问题就处在close（）的第2步，当LeaseChecker线程正在sleep时，该interrupt exception 将会被catch住，打印一条debug的error msg。如果恰好是Lease checker在renew（），DFSClient同nn通信的socket被interrupt.

Client.java 的wrapException（）会将socket被interrupted 的 exception捕获，并转为IOException丢出，该IOException冲过重重包围，最终被DFSClient中的 LeaseChecker抓获。并扔出个 LOG.warn("Problem renewing lease for " + clientName, ie);

对于被close（），而未来的及释放的lease， lease manager会有一个线程moniter，周期性检查该lease是否超过 hard limit(1小时)。如果超过则将该lease remove掉。

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附1 ：Thread interrupt()的jdk说明

If this thread is blocked in a java.nio.channels.Selector then the thread's interrupt status will be set and it will return immediately from the selection operation, possibly with a non-zero value, just as if the selector's wakeup method were invoked.

附2. exception stack：

10/04/05 11:18:20 WARN hdfs.DFSClient: Problem renewing lease for DFSClient_591364472

java.io.IOException: Call to hdpnn/10.249.54.101:9000 failed on local exception: java.io.InterruptedIOException: Interruped while waiting for IO on channel java.nio.channels.SocketChannel[connected local=/172.23.113.43:30811 remote=hdpnn/10.249.54.101:9000]. 60000 millis timeout left.

at org.apache.hadoop.ipc.Client.wrapException(Client.java:732)

at org.apache.hadoop.ipc.Client.call(Client.java:700)

at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:216)

at $Proxy0.renewLease(Unknown Source)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:82)

at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:59)

at $Proxy0.renewLease(Unknown Source)

at org.apache.hadoop.hdfs.DFSClient$LeaseChecker.renew(DFSClient.java:958)

at org.apache.hadoop.hdfs.DFSClient$LeaseChecker.run(DFSClient.java:970)

at java.lang.Thread.run(Thread.java:619)

Caused by: java.io.InterruptedIOException: Interruped while waiting for IO on channel java.nio.channels.SocketChannel[connected local=/172.23.113.43:30811 remote=hdpnn/10.249.54.101:9000]. 60000 millis timeout left.

at org.apache.hadoop.net.SocketIOWithTimeout$SelectorPool.select(SocketIOWithTimeout.java:277)

at org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:155)

at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:150)

at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:123)

at java.io.FilterInputStream.read(FilterInputStream.java:116)

at org.apache.hadoop.ipc.Client$Connection$PingInputStream.read(Client.java:272)

at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)

at java.io.BufferedInputStream.read(BufferedInputStream.java:237)

at java.io.DataInputStream.readInt(DataInputStream.java:370)

at org.apache.hadoop.ipc.Client$Connection.receiveResponse(Client.java:494)

at org.apache.hadoop.ipc.Client$Connection.run(Client.java:439)