Arko, Change Iterator to Iterable
George On 2012/04/18 8:16, Arko Provo Mukherjee wrote:
Hello, Thanks everyone for helping me. Here are my observations: Devaraj - I didn't find any bug in the log files. In fact, none of the print statements in my reducer are even appearing in the logs. I can share the syslogs if you want. I didn't paste them here so that the email doesn't get cluttered. Kasi - Thanks for the suggestion. I tired but got the same output. The system just created 1 reducer as my test data set is small. Bejoy - Can you please advice how I can pinpoint whether the IdentityReducer is being used or not. Steven - I tried compiling with your suggestion. However if I put a @Override on top of my reduce method, I get the following error: "method does not override or implement a method from a supertype" The code compiles without it. I do have an @Override on top of my map method though. public class Reduce_First extends Reducer<IntWritable, Text, NullWritable, Text> { public void reduce (IntWritable key, Iterator<Text> values, Context context) throws IOException, InterruptedException { while ( values.hasNext() ) // Process // Finally emit } } Thanks a lot again! Warm regards Arko On Tue, Apr 17, 2012 at 3:19 PM, Steven Willis<swil...@compete.com> wrote:Try putting @Override before your reduce method to make sure you're overriding the method properly. You’ll get a compile time error if not. -Steven Willis From: Bejoy KS [mailto:bejoy.had...@gmail.com] Sent: Tuesday, April 17, 2012 10:03 AM To: mapreduce-user@hadoop.apache.org Subject: Re: Reducer not firing Hi Akro From the naming of output files, your job has the reduce phase. But the reducer being used is the IdentityReducer instead of your custom reducer. That is the reason you are seeing the same map output in the output files as well. You need to evaluate your code and logs to see why IdentityReducer is being triggered. Regards Bejoy KS Sent from handheld, please excuse typos. ________________________________ From: kasi subrahmanyam<kasisubbu...@gmail.com> Date: Tue, 17 Apr 2012 19:10:33 +0530 To:<mapreduce-user@hadoop.apache.org> ReplyTo: mapreduce-user@hadoop.apache.org Subject: Re: Reducer not firing Could you comment the property where you are setting the number of reducer tasks and see the behaviour of the program once. If you already tried could you share the output On Tue, Apr 17, 2012 at 3:00 PM, Devaraj k<devara...@huawei.com> wrote: Can you check the task attempt logs in your cluster and find out what is happening in the reduce phase. By default task attempt logs present in $HADOOP_LOG_DIR/userlogs/<job-id>/. There could be some bug exist in your reducer which is leading to this output. Thanks Devaraj ________________________________________ From: Arko Provo Mukherjee [arkoprovomukher...@gmail.com] Sent: Tuesday, April 17, 2012 2:07 PM To: mapreduce-user@hadoop.apache.org Subject: Re: Reducer not firing Hello, Many thanks for the reply. The 'no_of_reduce_tasks' is set to 2. I have a print statement before the code I pasted below to check that. Also I can find two output files part-r-00000 and part-r-00001. But they contain the values that has been outputted by the Mapper logic. Please let me know what I can check further. Thanks a lot in advance! Warm regards Arko On Tue, Apr 17, 2012 at 12:48 AM, Devaraj k<devara...@huawei.com> wrote:Hi Arko, What is value of 'no_of_reduce_tasks'? If no of reduce tasks are 0, then the map task will directly write map output into the Job output path. Thanks Devaraj ________________________________________ From: Arko Provo Mukherjee [arkoprovomukher...@gmail.com] Sent: Tuesday, April 17, 2012 10:32 AM To: mapreduce-user@hadoop.apache.org Subject: Reducer not firing Dear All, I am porting code from the old API to the new API (Context objects) and run on Hadoop 0.20.203. Job job_first = new Job(); job_first.setJarByClass(My.class); job_first.setNumReduceTasks(no_of_reduce_tasks); job_first.setJobName("My_Job"); FileInputFormat.addInputPath( job_first, new Path (Input_Path) ); FileOutputFormat.setOutputPath( job_first, new Path (Output_Path) ); job_first.setMapperClass(Map_First.class); job_first.setReducerClass(Reduce_First.class); job_first.setMapOutputKeyClass(IntWritable.class); job_first.setMapOutputValueClass(Text.class); job_first.setOutputKeyClass(NullWritable.class); job_first.setOutputValueClass(Text.class); job_first.waitForCompletion(true); The problem I am facing is that instead of emitting values to reducers, the mappers are directly writing their output in the OutputPath and the reducers and not processing anything. As read from the online materials that are available both my Map and Reduce method uses the context.write method to emit the values. Please help. Thanks a lot in advance!! Warm regards Arko
