Provide a unified way to pass jobconf options from bin/hadoop
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Key: HADOOP-3722
URL: https://issues.apache.org/jira/browse/HADOOP-3722
Project: Hadoop Core
Issue Type: New Feature
Reporter: Matei Zaharia
Priority: Minor
Often when running a job it is useful to override some jobconf parameters from
jobconf.xml for that particular job - for example, setting the job priority,
setting the number of reduce tasks, setting the HDFS replication level, etc.
Currently the Hadoop examples, streaming, pipes, etc take these extra jobconf
parameters in different was: the examples in hadoop-examples.jar use
-Dkey=value, streaming uses -jobconf key=value, and pipes uses -jobconf
key1=value1,key2=value2,etc. Things would be simpler if bin/hadoop could take
the jobconf parameters itself, so that you could run for example bin/hadoop
-Dkey=value jar [whatever] as well as bin/hadoop -Dkey=value pipes [whatever].
This is especially useful when an organization needs to require users to use a
particular property, e.g. the name of a queue to use for scheduling in
HADOOP-3445. Otherwise, users may confuse one way of passing parameters with
another and may not notice that they forgot to include certain properties.
I propose adding support in bin/hadoop for jobconf options to be specified with
-C key=value. This would have the effect of setting hadoop.jobconf.key=value in
Java's system properties. The Configuration class would then be modified to
read any system properties that begin with hadoop.jobconf and override the
values in hadoop-site.xml.
I can write a patch for this pretty quickly if the design is sound. If there's
a better way of specifying jobconf parameters uniformly across Hadoop commands,
let me know.
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