One issue we have found with the jar process is that if the JAR file has
a main class specified, it is always used, regardless of the main
argument to the hadoop jar command - at least as of 0.15.1
Arun C Murthy wrote:
On Mon, Jan 07, 2008 at 08:24:36AM -0800, Lars George wrote:
Hi,
Maybe someone here can help me with a rather noob question. Where do I
have to put my custom jar to run it as a map/reduce job? Anywhere and
then specifying the HADOOP_CLASSPATH variable in hadoop-env.sh?
Once you have your jar and submit it for your job via the *hadoop jar* command
the framework takes care of distributing the software for nodes on which your
maps/reduces are scheduled:
$ hadoop jar <custom_jar> <custom_args>
The detail is that the framework copies your jar from the submission node to
the HDFS and then copies it onto the execution node.
Does http://lucene.apache.org/hadoop/docs/r0.15.1/mapred_tutorial.html#Usage
help?
Arun
Also, since I am using the Hadoop API already from our server code, it
seems natural to launch jobs from within our code. Are there any issue
with that? I assume I have to copy the jar files first and make them
available as per my question above, but then I am ready to start it from
my own code?
I have read most Wiki entries and while the actual workings are
described quite nicely, I could not find an answer to the questions
above. The demos are already in place and can be started as is without
the need of making them available.
Again, I apologize for being a noobie.
Lars
