Details
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Bug
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Status: Resolved
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Major
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Resolution: Won't Fix
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Description
Currently, pig creates temp dirs via call to FileLocalizer.getTemporaryPath. They are created on the client and are mainly used to store data between 2 M-R jobs. Pig then attempts to clean them up in the client's shutdown hook.
The problem with this approach is that, because there is now way to order the shutdown hooks, in some cases, the DFS is already closed when we try to delete the files in which case a substention amount of data can be left in DFS. I see this issue more frequently with hadoop 0.16 perhaps because I had to add an extra shutdown hook to handle hod disconnects.
The short term, I would like to propose the approach below:
(1) If trash is configured on the cluster, use trash location to create temp directory that will expire in 7 days. The hope is that most jobs don't run longer that 7 days. The user can specify a longer interval via a command line switch
(2) If trash is not enabled on the cluster, the location that we use now will be used
(3) In the shutdown hook, we will attempt to cleanup. If the attempt fails and trash is enabled, we let trash handle it; otherwise we provide the list of locations to the user to clean. (I realize that this is not ideal but could not figure out a better way.)
Longer term, I am talking with hadoop team to have better temp file support: https://issues.apache.org/jira/browse/HADOOP-2815
Comments? Suggestions?