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From Peyman Mohajerian <mohaj...@gmail.com>
Subject Re: println in MapReduce job
Date Thu, 24 Sep 2015 17:42:29 GMT
You log statement should show up in the container log for that Map class
within the data node. I'm guessing you aren't looking in the right place.

On Thu, Sep 24, 2015 at 9:54 AM, xeonmailinglist <xeonmailinglist@gmail.com>
wrote:

> Does anyone know this question about logging in MapReduce. I can't find an
> example or an explanation on how to print something inside user map and
> reduce functions.
>
> On 09/24/2015 04:19 PM, xeonmailinglist wrote:
>
> Hi,
>
>    1.
>
>    I have this example of MapReduce [1], and I want to print info in the
>    stdout and in a log file. It seems that the logs isn’t print anything. How
>    can I make my class print these words?
>    2.
>
>    I also have set in the yarn-site.xml to retain log. Although the logs
>    are retained in the /app-logs dir, the userlogs dir is deleted at the
>    end of the job execution. How can I make MapReduce to not delete files in
>    the userlogs dir?
>
> I am using Yarn.
>
> Thanks,
>
> [1] Wordcount exampla with just the map part.
>
>
> public class MyWordCount {
>     public static class MyMap extends Mapper {
>         Log log = LogFactory.getLog(MyWordCount.class);
>         private final static IntWritable one = new IntWritable(1);
>         private Text word = new Text();
>
>         public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable>
output, Reporter reporter) throws IOException {
>             StringTokenizer itr = new StringTokenizer(value.toString());
>             System.out.println("HERRE");
>             log.info("HERRRRRE");
>             while (itr.hasMoreTokens()) {
>                 word.set(itr.nextToken());
>                 output.collect(word, one);
>             }
>         }
>
>         public void run(Context context) throws IOException, InterruptedException {
>             setup(context);
>             try {
>                 while (context.nextKeyValue()) {
>                     System.out.println("Key: " + context.getCurrentKey() + " Value: "
+ context.getCurrentValue());
>                     map(context.getCurrentKey(), context.getCurrentValue(), context);
>                 }
>             } finally {
>                 cleanup(context);
>             }
>         }
>
>         public void cleanup(Mapper.Context context) {}
>     }
>
> [2] yarn-site.xml
>
>         <!-- job history -->
>         <property> <name>yarn.log-aggregation-enable</name> <value>true</value>
</property>
>         <property> <name>yarn.nodemanager.log.retain-seconds</name>
<value>900000</value> </property>
>         <property> <name>yarn.nodemanager.remote-app-log-dir</name>
<value>/app-logs</value> </property>
>
> ​
>
>
>

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