Search code examples
javahadoopmapreduce

Hadoop DistributedCache is deprecated - what is the preferred API?

My map tasks need some configuration data, which I would like to distribute via the Distributed Cache.

The Hadoop MapReduce Tutorial shows the usage of the DistributedCache class, roughly as follows:

// In the driver
JobConf conf = new JobConf(getConf(), WordCount.class);
...
DistributedCache.addCacheFile(new Path(filename).toUri(), conf); 

// In the mapper
Path[] myCacheFiles = DistributedCache.getLocalCacheFiles(job);
...

However, DistributedCache is marked as deprecated in Hadoop 2.2.0.

What is the new preferred way to achieve this? Is there an up-to-date example or tutorial covering this API?

Solution

  • The APIs for the Distributed Cache can be found in the Job class itself. Check the documentation here: http://hadoop.apache.org/docs/stable2/api/org/apache/hadoop/mapreduce/Job.html The code should be something like 

    Job job = new Job();
...
job.addCacheFile(new Path(filename).toUri());

    In your mapper code: 

    Path[] localPaths = context.getLocalCacheFiles();
...