Adding the link to the tutorial. http://hadoop.apache.org/docs/current/hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduceTutorial.html
From: Gino Gu01 Sent: Monday, November 24, 2014 5:29 PM To: '[email protected]' Subject: An issue in MapReduce Tutorial There is one bug in WordCount v2.0 which is part of MapReduce Tutorial. How to reproduce: Run the application: $ bin/hadoop jar wc.jar WordCount2 /user/joe/wordcount/input /user/joe/wordcount/output It will throw Null Pointer Exception during map phase. Reason: Below highlighted line set the default value of wordcount.skip.patterns to true. But in the arguments we didn't pass the any patterns file, so the line for (URI patternsURI : patternsURIs) throws exception. public void setup(Context context) throws IOException, InterruptedException { conf = context.getConfiguration(); caseSensitive = conf.getBoolean("wordcount.case.sensitive", true); if (conf.getBoolean("wordcount.skip.patterns", true)) { URI[] patternsURIs = Job.getInstance(conf).getCacheFiles(); for (URI patternsURI : patternsURIs) { Path patternsPath = new Path(patternsURI.getPath()); String patternsFileName = patternsPath.getName().toString(); parseSkipFile(patternsFileName); } } } How to fix it: Change above highlighted line to conf.getBoolean("wordcount.skip.patterns", false)) **************** CAUTION - Disclaimer ***************** This e-mail contains PRIVILEGED AND CONFIDENTIAL INFORMATION intended solely for the use of the addressee(s). If you are not the intended recipient, please notify the sender by e-mail and delete the original message. Further, you are not to copy, disclose, or distribute this e-mail or its contents to any other person and any such actions are unlawful. This e-mail may contain viruses. Infosys has taken every reasonable precaution to minimize this risk, but is not liable for any damage you may sustain as a result of any virus in this e-mail. You should carry out your own virus checks before opening the e-mail or attachment. Infosys reserves the right to monitor and review the content of all messages sent to or from this e-mail address. Messages sent to or from this e-mail address may be stored on the Infosys e-mail system. ***INFOSYS******** End of Disclaimer ********INFOSYS***
