HDFS數據節點從NameNode的

斷開我從時間到時間了Cloudera管理器中的以下錯誤：HDFS數據節點從NameNode的

This DataNode is not connected to one or more of its NameNode(s).

和

The Cloudera Manager agent got an unexpected response from this role's web server.

（通常在一起，有時只是其中之一）

在大多數SO和Google中提到這些錯誤時，問題是配置問題（並且數據節點從不連接到名稱節點）

在我的情況下，數據節點通常在啓動時連接，但在一段時間後會鬆開連接 - 所以它看起來不是一個錯誤的配置。

還有其他的選擇嗎？
是否有可能強制數據節點重新連接到名稱節點？
是否有可能從數據節點「ping」名稱節點（模擬數據節點的連接嘗試）
它可能是某種資源問題（對於許多打開的文件\連接）？

樣品日誌（誤差變化不時）

2014-02-25 06:39:49,179 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: exception: 
java.net.SocketTimeoutException: 480000 millis timeout while waiting for channel to be ready for write. ch : java.nio.channels.SocketChannel[connected local=/10.56.144.18:50010 remote=/10.56.144.28:48089] 
     at org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:165) 
     at org.apache.hadoop.net.SocketOutputStream.write(SocketOutputStream.java:153) 
     at org.apache.hadoop.net.SocketOutputStream.write(SocketOutputStream.java:114) 
     at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendPacket(BlockSender.java:504) 
     at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendBlock(BlockSender.java:673) 
     at org.apache.hadoop.hdfs.server.datanode.DataXceiver.readBlock(DataXceiver.java:338) 
     at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opReadBlock(Receiver.java:92) 
     at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:64) 
     at org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:221) 
     at java.lang.Thread.run(Thread.java:662) 
2014-02-25 06:39:49,180 INFO org.apache.hadoop.hdfs.server.datanode.DataNode.clienttrace: src: /10.56.144.18:50010, dest: /10.56.144.28:48089, bytes: 132096, op: HDFS_READ, cliID: DFSClient_NONMAPREDUCE_1315770947_27, offset: 0, srvID: DS-990970275-10.56.144.18-50010-1384349167420, blockid: BP-1381780028-10.56.144.16-1384349161741:blk_-8718668700255896235_5121440, duration: 480291679056 
2014-02-25 06:39:49,180 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: DatanodeRegistration(10.56.144.18, storageID=DS-990970275-10.56.144.18-50010-1384349167420, infoPort=50075, ipcPort=50020, storageInfo=lv=-40;cid=cluster16;nsid=7043943;c=0):Got exception while serving BP-1381780028-10.56.144.16-1384349161741:blk_-8718668700255896235_5121440 to /10.56.144.28:48089 
java.net.SocketTimeoutException: 480000 millis timeout while waiting for channel to be ready for write. ch : java.nio.channels.SocketChannel[connected local=/10.56.144.18:50010 remote=/10.56.144.28:48089] 
     at org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:165) 
     at org.apache.hadoop.net.SocketOutputStream.write(SocketOutputStream.java:153) 
     at org.apache.hadoop.net.SocketOutputStream.write(SocketOutputStream.java:114) 
     at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendPacket(BlockSender.java:504) 
     at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendBlock(BlockSender.java:673) 
     at org.apache.hadoop.hdfs.server.datanode.DataXceiver.readBlock(DataXceiver.java:338) 
     at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opReadBlock(Receiver.java:92) 
     at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:64) 
     at org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:221) 
     at java.lang.Thread.run(Thread.java:662) 
2014-02-25 06:39:49,181 ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: host.com:50010:DataXceiver error processing READ_BLOCK operation src: /10.56.144.28:48089 dest: /10.56.144.18:50010 
java.net.SocketTimeoutException: 480000 millis timeout while waiting for channel to be ready for write. ch : java.nio.channels.SocketChannel[connected local=/10.56.144.18:50010 remote=/10.56.144.28:48089] 
     at org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:165) 
     at org.apache.hadoop.net.SocketOutputStream.write(SocketOutputStream.java:153) 
     at org.apache.hadoop.net.SocketOutputStream.write(SocketOutputStream.java:114) 
     at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendPacket(BlockSender.java:504) 
     at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendBlock(BlockSender.java:673) 
     at org.apache.hadoop.hdfs.server.datanode.DataXceiver.readBlock(DataXceiver.java:338) 
     at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opReadBlock(Receiver.java:92) 
     at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:64) 
     at org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:221) 
     at java.lang.Thread.run(Thread.java:662)

來源

2014-02-24 Ophir Yoktan

檢查hadoop是否處於安全模式或某種程度上它發生因爲此 –

它與安全模式不相關（通常發生在服務器不在安全模式時）某些數據節點已連接，有些未連接。有沒有特定的數據節點傾向於鬆動連接（每次它是不同的數據節點） –

任何連接問題？ –