submitJob method in JobClient of Hadoop throws null pointer

Question

I am tryng to execute a MapReduce job and I want to periodically poll its status. I am trying to use the submitJob(jobConf) method of Jobclient class in the code as follows

 JobConf conf = new JobConf(SampleJobClass.class)   
 JobClient j= new JobClient();
 j.setConf(conf);
 System.out.println("from conf" +j.getConf().toString());
 RunningJob submitJob=j.submitJob(conf);`

I keep getting a null pointer error at the line j.submitJob(conf) The error stack is :

Exception in thread "main" java.lang.NullPointerException
    at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:844)
    at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:818)

Can someone tell me how to solve this error?

Answer 1

I had this problem as well. But when i use j.runJob(conf); it works well. You can use the static function JobClient.runJob(conf); This is what i tried and it works

public static RunningJob runJob(JobConf job) throws IOException {
JobClient jc = new JobClient(job);
RunningJob rj = jc.submitJob(job);
try {
  if (!jc.monitorAndPrintJob(job, rj)) {
    throw new IOException("Job failed!");
  }
} catch (InterruptedException ie) {
  Thread.currentThread().interrupt();
}
return rj;

} So I use the submitJob funciton in this way:

JobClient jcli = new JobClient(jconf);
        RunningJob rJob = jcli.submitJob(jconf);
        while (true){
            Thread.sleep(5000);
            System.out.println(rJob);
            if (rJob.isComplete())
                break;
        }