Sometimes it is desirable for a Hadoop job to be configurable without recompiling/rewriting the source. This can be achieved:

• both Perl and Java: use environment variables – all environment variables are shared by the Hadoop job
• Java only: use Hadoop properties:
  1. when running the job, use /net/projects/hadoop/bin/hadoop job.jar -Dname1=value1 -Dname2=value2 … input output
  2. in the job, use job.getConfiguration.get(“name”, default) to get the value as String, or use one of getInt, getLong, getFloat, getRange, getFile, getStrings, …