I got a similar error before in one of my projects. I had to set the values for "mapred.output.key.class" and "mapred.output.value.class".
That resolved the issue for me. Srihari On Jan 26, 2011, at 10:09 AM, Pedro Costa wrote: Yes, I can reproduce it deterministically. But, I also did some changes to the Hadoop MR code. Most definitely this is the reason. I'm looking throughly through the code. I'll say something after I find the problem. I was just wondering if this error has happened to someone before. Maybe I could get a hint and try to see what's my problem easily. Thanks, On Wed, Jan 26, 2011 at 6:02 PM, Tsz Wo (Nicholas), Sze <s29752-hadoopu...@yahoo.com<mailto:s29752-hadoopu...@yahoo.com>> wrote: Hi Pedro, This is interesting. Which version of Hadoop are you using? And where did you get the example class files? Also, are you able to reproduce it deterministically? Nicholas ________________________________ From: Pedro Costa <psdc1...@gmail.com<mailto:psdc1...@gmail.com>> To: mapreduce-user@hadoop.apache.org<mailto:mapreduce-user@hadoop.apache.org> Sent: Wed, January 26, 2011 5:47:01 AM Subject: PiEstimator error - Type mismatch in key from map Hi, I run the PI example of hadoop, and I've got the following error: [code] java.io.IOException: Type mismatch in key from map: expected org.apache.hadoop.io.BooleanWritable, recieved org.apache.hadoop.io.LongWritable at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:885) at org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:551) at org.apache.hadoop.mapreduce.TaskInputOutputContext.write(TaskInputOutputContext.java:81) at org.apache.hadoop.mapreduce.Mapper.map(Mapper.java:124) at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144) at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:637) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:343) at org.apache.hadoop.mapred.Child.main(Child.java:190) [/code] I've look at the map function of the class "PiEstimator.class" and it seems ok. [code] public void map(LongWritable offset, LongWritable size, OutputCollector<BooleanWritable, LongWritable> out, Reporter reporter) throws IOException {} [/code] What's wrong with this examples? Thanks, -- Pedro -- Pedro
