How to specify system property in hadoop except mo

Question

I'd like to set system property (not hadoop property) when running hadoop jobs. I found that it's not easy to setting system property. Even I set the property in shell

export HADOOP_OPTS="$HADOOP_OPTS:-Dproperty=value"

It's still not working. The "-D" option of hadoop command line is only for Configuration, not system property. So the "-D" option also not working

Anyone has ideas ? thanks

Answer 1

Check the difference between system properties and the environment variables and how to set them here.

Answer 2

Why not simply use -Dfoo.bar=example in-line when starting the job via command line, like so:

hadoop jar example.jar com.example.ExampleTool -Dfoo.bar=example argument

In order to get at the property in code, use conf.get("foo.bar");

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Now if you genuinely need it to be set as a system property, you can set it at the start of your code using the value you got from Hadoop config like so:

String property = conf.get("foo.bar");
System.setProperty("foo.bar", property);

Answer 3

The hadoop script invoke java class like this

exec "$JAVA" $JAVA_HEAP_MAX $HADOOP_OPTS $CLASS "$@"

so, we can pass system-wide property like this:

export HADOOP_OPTS="$HADOOP_OPTS -Dfoo=bar"