[jira] [Created] (MAPREDUCE-6874) Make DistributedCache check if the content of a directory has changed

["Attila Sasvari (JIRA)" <ji...@apache.org>]

Attila Sasvari created MAPREDUCE-6874:
-----------------------------------------

             Summary: Make DistributedCache check if the content of a directory has changed
                 Key: MAPREDUCE-6874
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6874
             Project: Hadoop Map/Reduce
          Issue Type: New Feature
            Reporter: Attila Sasvari


DistributedCache does not check recursively if the content a directory has changed when adding files to it with {{DistributedCache.addCacheFile()}}. 

h5. Background
I have an Oozie workflow on HDFS:
{code}
example_workflow
├── job.properties
├── lib
│   ├── components
│   │   ├── sub-component.sh
│   │   └── subsub
│   │       └── subsub.sh
│   ├── main.sh
│   └── sub.sh
└── workflow.xml
{code}
Executed the workflow; then made some changes in {{subsub.sh}}. Replaced the file on HDFS. When I re-ran the workflow, DistributedCache did not notice the changes as the timestamp on the {{components}} directory did not change. As a result, the old script was materialized.

This behaviour might be related to [determineTimestamps() |https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/filecache/ClientDistributedCacheManager.java#L84].
In order to use the new script during workflow execution, I had to update the whole {{components}} directory.


h6. Some more info:
In Oozie, [DistributedCache.addCacheFile() |https://github.com/apache/oozie/blob/master/core/src/main/java/org/apache/oozie/action/hadoop/JavaActionExecutor.java#L625] is used to add files to the distributed cache.



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