How to Run an Elastic MapReduce Job Using the Java SDK

The current Amazon EMR documentation provides a lot of coverage of how to run a Hadoop custom jar using the AWS management console. This post covers how you do the same thing directly using the EC2 SDK for Java on Eclipse.


To run the sample code, you need to set up and/or have knowledge of the following:

Running the Example Code

In order to run the example code below, please follow these setup steps:

  1. In Eclipse, select File -> New -> Other, and then search for AWS Java Project.
  2. Click Next, select a project name, select any other examples you want (S3, etc.) and enter your AWS Credentials.
  3. Click Next, then Finish.
  4. When the new project opens, right click on the (default package) -> New -> Class
  5. Enter the class name “ElasticMapReduceApp” and click Finish.
  6. Copy and paste the sample code below into the new class.
  7. Replace the string “your-bucket-name” with your S3 bucket name.
  8. Run the class.  It will report status as it runs.

After the run, the job output and job logs should appear as sub-directories under your S3 bucket.

Sample Code

import java.util.Arrays;
import java.util.Date;
import java.util.List;
import java.util.UUID;

import com.amazonaws.AmazonServiceException;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.PropertiesCredentials;

 * Run the Amazon Cloudburst example directly using the AWS SDK for Java.
 * @author mpouttuclarke
public class ElasticMapReduceApp

    private static final String HADOOP_VERSION = "0.20";
    private static final int INSTANCE_COUNT = 1;
    private static final String INSTANCE_TYPE = InstanceType.M1Large.toString();
    private static final UUID RANDOM_UUID = UUID.randomUUID();
    private static final String FLOW_NAME = "cloudburst-" + RANDOM_UUID.toString();
    private static final String BUCKET_NAME = "your-bucket-name";
    private static final String S3N_HADOOP_JAR =
    private static final String S3N_LOG_URI = "s3n://" + BUCKET_NAME + "/";
    private static final String[] JOB_ARGS =
        new String[] { "s3n://elasticmapreduce/samples/cloudburst/input/",
                      "s3n://" + BUCKET_NAME + "/" + FLOW_NAME, "36", "3", "0",
                      "24", "24", "128", "16" };
    private static final List<String> ARGS_AS_LIST = Arrays.asList(JOB_ARGS);
    private static final List<JobFlowExecutionState> DONE_STATES = Arrays
        .asList(new JobFlowExecutionState[] { JobFlowExecutionState.COMPLETED,
                                             JobFlowExecutionState.TERMINATED });
    static AmazonElasticMapReduce emr;

     * The only information needed to create a client are security credentials consisting of the AWS
     * Access Key ID and Secret Access Key. All other configuration, such as the service end points,
     * are performed automatically. Client parameters, such as proxies, can be specified in an
     * optional ClientConfiguration object when constructing a client.
     * @see com.amazonaws.auth.BasicAWSCredentials
     * @see com.amazonaws.auth.PropertiesCredentials
     * @see com.amazonaws.ClientConfiguration
    private static void init() throws Exception {
        AWSCredentials credentials = new PropertiesCredentials(

        emr = new AmazonElasticMapReduceClient(credentials);

    public static void main(String[] args) throws Exception {

        System.out.println("Welcome to the Elastic Map Reduce!");


        try {
            // Configure instances to use
            JobFlowInstancesConfig instances = new JobFlowInstancesConfig();
            System.out.println("Using EMR Hadoop v" + HADOOP_VERSION);
            System.out.println("Using instance count: " + INSTANCE_COUNT);
            System.out.println("Using master instance type: " + INSTANCE_TYPE);
            System.out.println("Using slave instance type: " + INSTANCE_TYPE);

            // Configure the job flow
            System.out.println("Configuring flow: " + FLOW_NAME);
            RunJobFlowRequest request = new RunJobFlowRequest(FLOW_NAME, instances);
            System.out.println("\tusing log URI: " + S3N_LOG_URI);

            // Configure the Hadoop jar to use
            System.out.println("\tusing jar URI: " + S3N_HADOOP_JAR);
            HadoopJarStepConfig jarConfig = new HadoopJarStepConfig(S3N_HADOOP_JAR);
            System.out.println("\tusing args: " + ARGS_AS_LIST);
            StepConfig stepConfig =
                new StepConfig(S3N_HADOOP_JAR.substring(S3N_HADOOP_JAR.indexOf('/') + 1),
            request.setSteps(Arrays.asList(new StepConfig[] { stepConfig }));

            //Run the job flow
            RunJobFlowResult result = emr.runJobFlow(request);

            //Check the status of the running job
            String lastState = "";
            STATUS_LOOP: while (true)
                DescribeJobFlowsRequest desc =
                    new DescribeJobFlowsRequest(
                                                Arrays.asList(new String[] { result.getJobFlowId() }));
                DescribeJobFlowsResult descResult = emr.describeJobFlows(desc);
                for (JobFlowDetail detail : descResult.getJobFlows())
                    String state = detail.getExecutionStatusDetail().getState();
                    if (isDone(state))
                        System.out.println("Job " + state + ": " + detail.toString());
                        break STATUS_LOOP;
                    else if (!lastState.equals(state))
                        lastState = state;
                        System.out.println("Job " + state + " at " + new Date().toString());
        } catch (AmazonServiceException ase) {
                System.out.println("Caught Exception: " + ase.getMessage());
                System.out.println("Reponse Status Code: " + ase.getStatusCode());
                System.out.println("Error Code: " + ase.getErrorCode());
                System.out.println("Request ID: " + ase.getRequestId());

     * @param state
     * @return
    public static boolean isDone(String value)
        JobFlowExecutionState state = JobFlowExecutionState.fromValue(value);
        return DONE_STATES.contains(state);

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