CODEWITHSUNDEEP
mapreduce
byron1st
byron1st

Reputation: 981

Executing multiple jobs in Map/Reduce program of Hadoop

public int run(String[] args) throws Exception {

    /*****************Job for id-title mapping*******************/      

    JobConf conf_idTitle = new JobConf(PageRank.class);
    conf_idTitle.setJobName("first_idTitleMapping");

    ...

    FileInputFormat.setInputPaths(conf_idTitle, new Path(args[0]));
    FileOutputFormat.setOutputPath(conf_idTitle, new Path(pathforIdTitle));

    JobClient.runJob(conf_idTitle);

    /*****************Job for linkgraph mapping*******************/

    JobConf conf_linkgraph = new JobConf(PageRank.class);

    conf_linkgraph.setJobName("second_linkgraphBuilding");

    ...

    FileInputFormat.setInputPaths(conf_linkgraph, new Path(args[0]));
    FileOutputFormat.setOutputPath(conf_linkgraph, new Path(pathforLinkgraph));

    JobClient.runJob(conf_linkgraph);

    return 0;
}

public static void main(String[] args) throws Exception {
     int res = ToolRunner.run(new Configuration(), new PageRank(), args);
     System.exit(res);
}

This code is for executing two jobs in Map/reduce program serially, not in parellel. I uses different mappers and reducers for each job, so I defined two JobConf objects. Because I should use the output of the first job as the input of the second job, I defined second JobConf objects after 'JobClient.runJob(conf_idTitle);'.

However, I got an exception like below:

    java.lang.RuntimeException: Error in configuring object
at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:93)
at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:64)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:117)
at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:387)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:325)
at org.apache.hadoop.mapred.Child$4.run(Child.java:270)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1157)
at org.apache.hadoop.mapred.Child.main(Child.java:264)
    Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.jav

Why this error emerged? Thanks in advance.

Upvotes: 1

Views: 587

Answers (1)

shiva kumar s
shiva kumar s

Reputation: 169

public JobConf(Configuration conf)

This constructor is commonly used when your application already has constructed a JobConf object and wants a copy to use for an alternate job. The configuration in conf is copied into the new JobConf object.

Upvotes: 1

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