内容简介:堆栈信息:解决方法:产生问题的原因是读取 DataNode 的并发过大,导致 Socket 连接超时。解决的办法有两个:
问题一:HDFS 读超时
堆栈信息:
java.net.SocketTimeoutException: 60000 millis timeout while waiting for channel to be ready for read. ch : java.nio.channels.SocketChannel[connected local=/xxx.xxx.xxxx.xxx:36622 remote=/xxx.xxx.xxx.xxx:50010] at org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:164) at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:161) at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:131) at org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:118) at java.io.FilterInputStream.read(FilterInputStream.java:83) at org.apache.hadoop.hdfs.protocolPB.PBHelper.vintPrefixed(PBHelper.java:2239) at org.apache.hadoop.hdfs.RemoteBlockReader2.newBlockReader(RemoteBlockReader2.java:430) at org.apache.hadoop.hdfs.BlockReaderFactory.getRemoteBlockReader(BlockReaderFactory.java:881) at org.apache.hadoop.hdfs.BlockReaderFactory.getRemoteBlockReaderFromTcp(BlockReaderFactory.java:759) at org.apache.hadoop.hdfs.BlockReaderFactory.build(BlockReaderFactory.java:376) at org.apache.hadoop.hdfs.DFSInputStream.blockSeekTo(DFSInputStream.java:662) at org.apache.hadoop.hdfs.DFSInputStream.readWithStrategy(DFSInputStream.java:889) at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:942) at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:742) at java.io.DataInputStream.readByte(DataInputStream.java:265) at org.apache.hadoop.io.WritableUtils.readVLong(WritableUtils.java:308) at org.apache.hadoop.io.WritableUtils.readVIntInRange(WritableUtils.java:348) at org.apache.hadoop.io.Text.readString(Text.java:471) at org.apache.hadoop.io.Text.readString(Text.java:464)
解决方法:
产生问题的原因是读取 DataNode 的并发过大,导致 Socket 连接超时。解决的办法有两个:
dfs.client.socket-timeout dfs.datanode.handler.count
问题二:最后一个 block 没有足够的副本数,文件关闭失败
堆栈信息:
java.io.IOException: Unable to close file because the last block does not have enough number of replicas. at org.apache.hadoop.hdfs.DFSOutputStream.completeFile(DFSOutputStream.java:2528) at org.apache.hadoop.hdfs.DFSOutputStream.closeImpl(DFSOutputStream.java:2495) at org.apache.hadoop.hdfs.DFSOutputStream.close(DFSOutputStream.java:2458) at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.close(FSDataOutputStream.java:72) at org.apache.hadoop.fs.FSDataOutputStream.close(FSDataOutputStream.java:106)
解决办法:
NameNode 收到 HDFS 客户端关闭文件请求之后,会检查最后一个 block 的完成状态,只有当足够的 DataNode 上报 block 完成才可关闭文件。
网络 IO 延迟和 GC 等原因都将导致 DataNode 延迟上报。
HDFS 客户端会多次尝试关闭文件,通过增加重试次数可减少该问题。编辑文件 hdfs-core.xml 文件,修改 dfs.client.block.write.locateFollowingBlock.retries
属性,默认为 5
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