[HADOOP-1513] A likely race condition between the creation of a directory and checking for its existence in the DiskChecker class

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 0.14.0
• Fix Version/s: 0.14.0
• Component/s: fs
• Assignee: Devaraj Das
• Reporter: Devaraj Das
• Created: 21/Jun/07 08:27
• Updated: 20/Aug/07 18:12
• Resolved: 02/Jul/07 18:04

Description

Got this exception in a job run. It looks like the problem is a race condition between the creation of a directory and checking for its existence. Specifically, the line:
if (!dir.exists() && !dir.mkdirs()), doesn't seem safe when invoked by multiple processes at the same time.

2007-06-21 07:55:33,583 INFO org.apache.hadoop.mapred.MapTask: numReduceTasks: 1
2007-06-21 07:55:33,818 WARN org.apache.hadoop.fs.AllocatorPerContext: org.apache.hadoop.util.DiskChecker$DiskErrorException: can not create directory: /export/crawlspace/kryptonite/ddas/dfs/data/tmp
at org.apache.hadoop.util.DiskChecker.checkDir(DiskChecker.java:26)
at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.createPath(LocalDirAllocator.java:211)
at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.getLocalPathForWrite(LocalDirAllocator.java:248)
at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.createTmpFileForWrite(LocalDirAllocator.java:276)
at org.apache.hadoop.fs.LocalDirAllocator.createTmpFileForWrite(LocalDirAllocator.java:155)
at org.apache.hadoop.dfs.DFSClient$DFSOutputStream.newBackupFile(DFSClient.java:1171)
at org.apache.hadoop.dfs.DFSClient$DFSOutputStream.(DFSClient.java:1136)
at org.apache.hadoop.dfs.DFSClient.create(DFSClient.java:342)
at org.apache.hadoop.dfs.DistributedFileSystem$RawDistributedFileSystem.create(DistributedFileSystem.java:145)
at org.apache.hadoop.fs.ChecksumFileSystem$FSOutputSummer.(ChecksumFileSystem.java:368)
at org.apache.hadoop.fs.ChecksumFileSystem.create(ChecksumFileSystem.java:443)
at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:254)
at org.apache.hadoop.io.SequenceFile$Writer.(SequenceFile.java:675)
at org.apache.hadoop.io.SequenceFile.createWriter(SequenceFile.java:165)
at org.apache.hadoop.examples.RandomWriter$Map.map(RandomWriter.java:137)
at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:46)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:189)
at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:1740)

2007-06-21 07:55:33,821 WARN org.apache.hadoop.mapred.TaskTracker: Error running child

Issue Links

• relates to: HDFS-72 IOException at task startup "No valid local directories in property: dfs.client.buffer.dir"