JavaHadoop2。2.0追加文件发生AlreadyBeingCreatedException

9 月 Questions & Answers 5537

我遇到了一个关于hadoop2的问题。2.0追加操作。我通过hdfs java API将一些字节附加到hdfs文件中。首先，如果在附加操作之前文件不存在，我将创建目标文件，代码如下：

String fileUri = "hdfs://hadoopmaster:9000/in/append_test.txt";
// create the hdfs file, if not exists
HdfsClient.createPathIfNotExist(fileUri);
// do 5 times append operation
for (int i=0; i<5; i++){
    HdfsClient.appendTo(fileUri, ("append content"+i).getBytes("UTF-8"));
}

createPathIfNotExist函数：

Path p = null;
FileSystem fs = null;
try {
    fs = FileSystem.get(URI.create(uri), conf);
    p = new Path(uri);
    if (!fs.exists(p)) {
    if (uri.charAt(uri.length() - 1) == '/'){ //create a directory
        if(fs.mkdirs(p)){
               // create successfully
            }
        }else{ //create a file
        FSDataOutputStream fos = fs.create(p);
            fos.close();
        }
    } else{
        System.out.println(uri + "existing");
    }
} catch (IOException e) {
    e.printStackTrace();
} finally{
    if (fs != null)
    try {
       fs.close();
       fs = null;
    } catch (IOException e) {
       e.printStackTrace();
        }
}

appendTo函数：

ByteArrayInputStream in = null;
OutputStream out = null;
FileSystem fs = null;
try {
   in = new ByteArrayInputStream(bytes);
   fs = FileSystem.get(URI.create(uri), conf);
   out = fs.append(new Path(uri)); //get append outputstream
   IOUtils.copyBytes(in, out, bufferSize, false);
} catch(Exception e){
   e.printStackTrace();
} finally{
   if (in != null) IOUtils.closeStream(in);
   if (out != null) IOUtils.closeStream(out);
   if (fs != null){
    try {
           fs.close();
           fs = null;
    } catch (IOException e) {
       e.printStackTrace();
    }
   }
}

结果是附加_测试。已创建txt，但内容只有：

append content0

并出现例外情况：

org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException): Failed to create file [/in/append_test.txt] for [DFSClient_NONMAPREDUCE_-1148656837_1] on client [192.168.141.1], because this file is already being created by [DFSClient_NONMAPREDUCE_2099912242_1] on [192.168.141.1]
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.recoverLeaseInternal(FSNamesystem.java:2320)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.appendFileInternal(FSNamesystem.java:2153)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.appendFileInt(FSNamesystem.java:2386)
        at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.appendFile(FSNamesystem.java:2347)
        at org.apache.hadoop.hdfs.server.namenode.NameNodeRpcServer.append(NameNodeRpcServer.java:508)
        at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolServerSideTranslatorPB.append(ClientNamenodeProtocolServerSideTranslatorPB.java:320)
        at org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos$ClientNamenodeProtocol$2.callBlockingMethod(ClientNamenodeProtocolProtos.java:59572)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:585)
        at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:928)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2048)
        at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2044)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:415)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1491)
        at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2042)

        at org.apache.hadoop.ipc.Client.call(Client.java:1347)
        at org.apache.hadoop.ipc.Client.call(Client.java:1300)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:206)
        at com.sun.proxy.$Proxy10.append(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        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.$Proxy10.append(Unknown Source)
        at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.append(ClientNamenodeProtocolTranslatorPB.java:245)
        at org.apache.hadoop.hdfs.DFSClient.callAppend(DFSClient.java:1480)
        at org.apache.hadoop.hdfs.DFSClient.append(DFSClient.java:1520)
        at org.apache.hadoop.hdfs.DFSClient.append(DFSClient.java:1508)
        at org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:310)
        at org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:306)
        at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
        at org.apache.hadoop.hdfs.DistributedFileSystem.append(DistributedFileSystem.java:306)
        at org.apache.hadoop.fs.FileSystem.append(FileSystem.java:1160)
        at org.lh.blog.message.hadoop.HdfsClient$2.run(HdfsClient.java:130)
        at org.lh.blog.message.hadoop.HdfsClient$2.run(HdfsClient.java:1)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:356)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1471)
        at org.lh.blog.message.hadoop.HdfsClient.appendTo(HdfsClient.java:121)
        at org.lh.blog.message.hadoop.HdfsClient.appendTo(HdfsClient.java:110)
        at org.lh.blog.message.test.HdfsClientTests.testCreateFileBeforeAppend(HdfsClientTests.java:26)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
        at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
        at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
        at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
        at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

也就是说，它在创建不存在的文件后只执行了一次追加操作，其他4次追加操作失败，出现上述错误。我在append之前创建了这个文件，但是它说AlreadyBeingCreatedException，我有些困惑

我也有一些尝试。我找到了JavaAPI创建的hdfs文件，都不能做追加操作。但是由hdfs命令（etc，“hdfs dfs-put”）创建的hdfs文件可以执行追加操作

你能帮我，给我一些建议吗

多谢各位；问候

共 (3) 个答案

# 1 楼答案
您可以将推测操作设置为false
```
job.setSpeculativeExecution(false);
```
或者可以使用时间戳或路径中的任何其他变量将文件创建到某个临时位置，然后将结果合并到基本路径
# 2 楼答案

这个问题是由hadoop“附加代码”中的一些错误引起的。您可以在本文中阅读更多关于这方面的内容： append content to a file in HDFS

也为这个问题提供了解决方案。您还可以在创建文件之后对fs调用close（）方法，并在追加操作之前再次获取文件系统。对我来说很好，但这取决于你
# 3 楼答案
为了解决这个问题,
1. 读取文件内容并将其存储到变量中
2. 添加要附加到此变量的新内容
3. 重新创建文件并将内容写回
这个过程对我来说很好，解决了这个问题

追加操作代价很高，如果您试图并行尝试，那么就会出现这个问题。因此，重新创建文件并将内容重新写入其中，而不是追加

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JavaHadoop2。2.0追加文件发生AlreadyBeingCreatedException

共 (3) 个答案

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# 3 楼答案