Attila Sasvari created MAPREDUCE-6874:
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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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