> I have a simple MR job, and I want each Mapper to get one line from my input file (which contains further instructions for lengthy processing).
Use the NLineInputFormat class. http://hadoop.apache.org/mapreduce/docs/r0.21.0/api/org/apache/hadoop/mapreduce/lib/input/NLineInputFormat.html Praveen On Thu, Feb 2, 2012 at 9:43 AM, Mark Kerzner <[email protected]>wrote: > Thanks! > Mark > > On Wed, Feb 1, 2012 at 7:44 PM, Anil Gupta <[email protected]> wrote: > > > Yes, if ur block size is 64mb. Btw, block size is configurable in Hadoop. > > > > Best Regards, > > Anil > > > > On Feb 1, 2012, at 5:06 PM, Mark Kerzner <[email protected]> > wrote: > > > > > Anil, > > > > > > do you mean one block of HDFS, like 64MB? > > > > > > Mark > > > > > > On Wed, Feb 1, 2012 at 7:03 PM, Anil Gupta <[email protected]> > > wrote: > > > > > >> Do u have enough data to start more than one mapper? > > >> If entire data is less than a block size then only 1 mapper will run. > > >> > > >> Best Regards, > > >> Anil > > >> > > >> On Feb 1, 2012, at 4:21 PM, Mark Kerzner <[email protected]> > > wrote: > > >> > > >>> Hi, > > >>> > > >>> I have a simple MR job, and I want each Mapper to get one line from > my > > >>> input file (which contains further instructions for lengthy > > processing). > > >>> Each line is 100 characters long, and I tell Hadoop to read only 100 > > >> bytes, > > >>> > > >>> > > >> > > > job.getConfiguration().setInt("mapreduce.input.linerecordreader.line.maxlength", > > >>> 100); > > >>> > > >>> I see that this part works - it reads only one line at a time, and > if I > > >>> change this parameter, it listens. > > >>> > > >>> However, on a cluster only one node receives all the map tasks. Only > > one > > >>> map tasks is started. The others never get anything, they just wait. > > I've > > >>> added 100 seconds wait to the mapper - no change! > > >>> > > >>> Any advice? > > >>> > > >>> Thank you. Sincerely, > > >>> Mark > > >> > > >
