当我提交 distcp 作业以将文件从不安全的 hadoop 集群复制到安全（kerberized）集群时，我遇到了以下错误：
2017-08-28 17:42:09,526 FATAL [IPC Server handler 0 on 42131] org.apache.hadoop.mapred.TaskAttemptListenerImpl: Task: attempt_1503655816205_0288_m_000000_0 - exited : java.io.IOException: File copy failed: webhdfs://source/path --> webhdfs://target/path
at org.apache.hadoop.tools.mapred.CopyMapper.copyFileWithRetry(CopyMapper.java:284)
at org.apache.hadoop.tools.mapred.CopyMapper.map(CopyMapper.java:252)
at org.apache.hadoop.tools.mapred.CopyMapper.map(CopyMapper.java:50)
at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:787)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1714)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.io.IOException: Couldn't run retriable-command: Copying webhdfs://source/path to webhdfs://target/path
at org.apache.hadoop.tools.util.RetriableCommand.execute(RetriableCommand.java:101)
at org.apache.hadoop.tools.mapred.CopyMapper.copyFileWithRetry(CopyMapper.java:280)
... 10 more
Caused by: java.io.IOException: Error writing request body to server
at sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.checkError(HttpURLConnection.java:3479)
at sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.write(HttpURLConnection.java:3462)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
at java.io.BufferedOutputStream.write(BufferedOutputStream.java:121)
at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.write(FSDataOutputStream.java:58)
at java.io.DataOutputStream.write(DataOutputStream.java:107)
at java.io.BufferedOutputStream.write(BufferedOutputStream.java:122)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.copyBytes(RetriableFileCopyCommand.java:257)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.copyToFile(RetriableFileCopyCommand.java:184)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.doCopy(RetriableFileCopyCommand.java:124)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.doExecute(RetriableFileCopyCommand.java:100)
at org.apache.hadoop.tools.util.RetriableCommand.execute(RetriableCommand.java:87)
... 11 more
2017-08-28 17:42:09,526 INFO [IPC Server handler 0 on 42131] org.apache.hadoop.mapred.TaskAttemptListenerImpl: Diagnostics report from attempt_1503655816205_0288_m_000000_0: Error: java.io.IOException: File copy failed: webhdfs://source/path --> webhdfs://target/path
at org.apache.hadoop.tools.mapred.CopyMapper.copyFileWithRetry(CopyMapper.java:284)
at org.apache.hadoop.tools.mapred.CopyMapper.map(CopyMapper.java:252)
at org.apache.hadoop.tools.mapred.CopyMapper.map(CopyMapper.java:50)
at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:787)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1714)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.io.IOException: Couldn't run retriable-command: Copying webhdfs://source/path to webhdfs://target/path
at org.apache.hadoop.tools.util.RetriableCommand.execute(RetriableCommand.java:101)
at org.apache.hadoop.tools.mapred.CopyMapper.copyFileWithRetry(CopyMapper.java:280)
... 10 more
Caused by: java.io.IOException: Error writing request body to server
at sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.checkError(HttpURLConnection.java:3479)
at sun.net.www.protocol.http.HttpURLConnection$StreamingOutputStream.write(HttpURLConnection.java:3462)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82)
at java.io.BufferedOutputStream.write(BufferedOutputStream.java:121)
at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.write(FSDataOutputStream.java:58)
at java.io.DataOutputStream.write(DataOutputStream.java:107)
at java.io.BufferedOutputStream.write(BufferedOutputStream.java:122)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.copyBytes(RetriableFileCopyCommand.java:257)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.copyToFile(RetriableFileCopyCommand.java:184)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.doCopy(RetriableFileCopyCommand.java:124)
at org.apache.hadoop.tools.mapred.RetriableFileCopyCommand.doExecute(RetriableFileCopyCommand.java:100)
at org.apache.hadoop.tools.util.RetriableCommand.execute(RetriableCommand.java:87)
... 11 more
由于Error writing request body to server消息太宽泛，我不知道要挖掘什么。这里有什么提示吗？
仅供参考，我在安全集群上测试了 mapreduce pi 示例，它工作正常。