Dfs client name for a map/reduce task should have some randomness -----------------------------------------------------------------
Key: HDFS-1526 URL: https://issues.apache.org/jira/browse/HDFS-1526 Project: Hadoop HDFS Issue Type: Bug Components: hdfs client Reporter: Hairong Kuang Assignee: Hairong Kuang Fix For: 0.23.0 Fsck shows one of the files in our dfs cluster is corrupt. # /bin/hadoop fsck aFile -files -blocks -locations aFile: 4633 bytes, 2 block(s): aFile: CORRUPT block blk_-4597378336099313975 OK 0. blk_-4597378336099313975_2284630101 len=0 repl=3 [...] 1. blk_5024052590403223424_2284630107 len=4633 repl=3 [...]Status: CORRUPT On disk, these two blocks are of the same size and the same content. It turns out the writer of the file is from a multiple threaded map task. Each thread may write to the same file. One possible interaction of two threads might make this to happen: [T1: create aFile] [T2: delete aFile] [T2: create aFile][T1: addBlock 0 to aFile][T2: addBlock1 to aFile]... Because T1 and T2 have the same client name, which is the map task id, the above interactions could be done without any lease exception, thus eventually leading to a corrupt file. To solve the problem, a mapreduce task's client name could be formed by its task id followed by a random number. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.