could only be replicated to 0 nodes instead of minReplication (=1)

今天在用程序通过hdfs拷贝数据至hadoop上的时候报了这个错误

SEVERE: Failed to close file /tmp/g65g65y7uu76d/17_
org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /tmp/g65g65y7uu76d/17_ could only be replicated to 0 nodes instead of minReplication (=1).  There are 5 datanode(s) running and no node(s) are excluded in this operation.
    at org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.chooseTarget4NewBlock(BlockManager.java:1549)
    at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.getAdditionalBlock(FSNamesystem.java:3200)
    at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.addBlock(NameNodeRpcServer.java:641)
    at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.addBlock(ClientNamenodeProtocolServerSideTranslatorPB.java:482)
    at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java)
    at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:619)
    at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:962)
    at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2039)
    at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2035)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
    at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2033)

    at org.apache.hadoop.ipc.Client.call(Client.java:1406)
    at org.apache.hadoop.ipc.Client.call(Client.java:1359)
    at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:206)
    at com.sun.proxy.$Proxy17.addBlock(Unknown Source)
    at sun.reflect.GeneratedMethodAccessor46.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:186)
    at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:102)
    at com.sun.proxy.$Proxy17.addBlock(Unknown Source)
    at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.addBlock(ClientNamenodeProtocolTranslatorPB.java:348)
    at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.locateFollowingBlock(DFSOutputStream.java:1264)
    at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:1112)
    at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:522)

当看到这个错误,以为可能是下面几个原因

1. datanode 挂了

2. datanode 没有空间了

3. datanode 与namenode或者客户端机的连接有问题

但是看了一下,没有这些问题.

接着在集群的客户端机上,通过命令行 

hadoop fs -put

来上传的一下相同的文件夹,并没有错.那么基本可以确定是程序的问题.

又检查了一遍代码,发现程序中是看拷贝的文件的有多少个part,就同时启动多少个线程并行.

觉得可能是同时打开的连接太多导致的,然后将线程固定在50个,再次执行,没问题了.

问题解决!

本次的问题是:

在使用API写数据至HDFS时,同时打开的连接太多,导致连接datanode时出错.