Help Center > > User Guide> Managing Active Clusters> Managing Jobs> Running a MapReduce Job

Running a MapReduce Job

Updated at: Nov 06, 2019 GMT+08:00

You can submit programs developed by yourself to MRS to execute them, and obtain the results. This section describes how to submit a MapReduce job on the MRS management console. MapReduce jobs are used to submit JAR programs to quickly process massive amounts of data in parallel and create a distributed data processing and execution environment.

If the job and file management functions are not supported on the cluster details page, submit the jobs in the background.

Prerequisites

You have uploaded the program packages and data files required for running jobs to OBS or HDFS.

Submitting a Job on the GUI

  1. Log in to the MRS management console.
  2. Choose Clusters > Active Clusters, select a running cluster, and click its name to switch to the cluster details page.
  3. If Kerberos authentication is enabled for the cluster, perform the following steps. If Kerberos authentication is not enabled for the cluster, skip this step.

    In the Basic Information area on the Dashboard tab page, click on the right side of IAM User Sync to synchronize IAM users. For details, see Synchronizing IAM Users to MRS.

    • In MRS 2.0.1 or versions earlier than MRS 1.8.7, the job management function is unavailable in a cluster with Kerberos authentication enabled. You need to submit a job in the background.
    • When the policy of the user group to which the IAM user belongs changes from MRS Viewer to MRS User, MRS Admin, or MRS Administrator, wait for 5 minutes until the new policy takes effect after the synchronization is complete because the sssd cache of cluster nodes needs time to be updated. Then, submit a job. Otherwise, the job may fail to be submitted.
    • When the policy of the user group to which the IAM user belongs changes from MRS User, MRS Admin, or MRS Administrator to MRS Viewer, wait for 5 minutes until the new policy takes effect after the synchronization is complete because the sssd cache of cluster nodes needs time to be updated.

  4. Click the Jobs tab.
  5. Click Create. The Create Job page is displayed.
  6. In Type, select MapReduce. Configure other job information.

    • If the cluster version is MRS 1.8.7 or later than MRS 2.0.1, configure MapReduce job information by referring to Table 1.
    • If the cluster version is MRS 2.0.1 or earlier than MRS 1.8.7, configure MapReduce job information by referring to Table 2.
      Table 1 Job configuration information

      Parameter

      Description

      Name

      Job name. It contains 1 to 64 characters. Only letters, digits, hyphens (-), and underscores (_) are allowed.

      NOTE:

      You are advised to set different names for different jobs.

      Program Path

      Path of the program package to be executed. The following requirements must be met:

      • Contains a maximum of 1,023 characters, excluding special characters such as ;|&><'$. The parameter value cannot be empty or full of spaces.
      • The path of the program to be executed can be stored in HDFS or OBS. The path varies depending on the file system.
        • OBS: The path must start with s3a://. Example: s3a://wordcount/program/xxx.jar
        • HDFS: The path must start with /user.
      • For SparkScript and HiveScript, the path must end with .sql. For MapReduce, the path must end with .jar. For Flink and SparkSubmit, the path must end with .jar or .py. The .sql, .jar, and .py are case-insensitive.

      Parameters

      Key parameters for program execution. Multiple parameters are separated by space.

      Configuration method: Program class name Data input path Data output path

      • Program class name: It is specified by a function in your program. MRS is responsible for transferring parameters only.
      • Data input path: Click HDFS or OBS to select a path.
      • Data output path: Click HDFS or OBS to select a path.

      The parameter contains a maximum of 2,047 characters, excluding special characters such as ;|&><'$, and can be left blank.

      NOTE:

      When entering a parameter containing sensitive information (for example, login password), you can add an at sign (@) before the parameter name to encrypt the parameter value. This prevents the sensitive information from being persisted in plaintext. When you view job information on the MRS management console, the sensitive information is displayed as *.

      Example: username=admin @password=admin_123

      Service Parameter

      This parameter is optional. It is used to modify service parameters for the job. The parameter modification applies only to the current job. To make the modification take effect permanently for the cluster, follow instructions in Configuring Service Parameters.

      To add multiple parameters, click on the right. To delete a parameter, click Delete on the right.

      Command Reference

      Command submitted to the background for execution when a job is submitted

      Table 2 Job configuration information

      Parameter

      Description

      Name

      Job name. It contains 1 to 64 characters. Only letters, digits, hyphens (-), and underscores (_) are allowed.

      NOTE:

      You are advised to set different names for different jobs.

      Program Path

      Path of the program package to be executed. The following requirements must be met:

      • Contains a maximum of 1,023 characters, excluding special characters such as ;|&><'$. The parameter value cannot be empty or full of spaces.
      • The path of the program to be executed can be stored in HDFS or OBS. The path varies depending on the file system.
        • OBS: The path must start with s3a://. Example: s3a://wordcount/program/xxx.jar
        • HDFS: The path must start with /user.
      • For SparkScript, the path must end with .sql. For MapReduce and Spark, the path must end with .jar. The .sql and .jar are case-insensitive.

      Parameters

      Key parameter for program execution. The parameter is specified by the function of the user's program. MRS is only responsible for loading the parameter. Multiple parameters are separated by space.

      Configuration method: Package name.Class name

      The parameter contains a maximum of 2,047 characters, excluding special characters such as ;|&><'$, and can be left blank.

      NOTE:

      When entering a parameter containing sensitive information (for example, login password), you can add an at sign (@) before the parameter name to encrypt the parameter value. This prevents the sensitive information from being persisted in plaintext. When you view job information on the MRS management console, the sensitive information is displayed as *.

      Example: username=admin @password=admin_123

      Import from

      Path for inputting data

      Data can be stored in HDFS or OBS. The path varies depending on the file system.
      • OBS: The path must start with s3a://.
      • HDFS: The path must start with /user.

      The parameter contains a maximum of 1,023 characters, excluding special characters such as ;|&>,<'$, and can be left blank.

      Export to

      Path for outputting data

      NOTE:
      • When setting this parameter, select OBS or HDFS. Select a file directory or manually enter a file directory, and click OK.
      • If you add the hadoop-mapreduce-examples-x.x.x.jar sample program or a program similar to hadoop-mapreduce-examples-x.x.x.jar, enter a directory that does not exist.
      Data can be stored in HDFS or OBS. The path varies depending on the file system.
      • OBS: The path must start with s3a://.
      • HDFS: The path must start with /user.

      The parameter contains a maximum of 1,023 characters, excluding special characters such as ;|&>,<'$, and can be left blank.

      Log Path

      Path for storing job logs that record job running status.

      Data can be stored in HDFS or OBS. The path varies depending on the file system.
      • OBS: The path must start with s3a://.
      • HDFS: The path must start with /user.

      The parameter contains a maximum of 1,023 characters, excluding special characters such as ;|&>,<'$, and can be left blank.

  7. Confirm job configuration information and click OK.

    After the job is created, you can manage it.

Submitting a Job in the Background

  1. Log in to the MRS management console.
  2. Choose Clusters > Active Clusters, select a running cluster, and click its name to switch to the cluster details page.
  3. On the Nodes tab page, click the name of a Master node to go to the ECS management console.
  4. Click Remote Login in the upper right corner of the page.
  5. Enter the username and password of the Master node as prompted. The username is root and the password is the one set during cluster creation.
  6. Run the following command to initialize environment variables:

    source /opt/client/bigdata_env

  7. If the Kerberos authentication is enabled for the current cluster, run the following command to authenticate the user. If the Kerberos authentication is disabled for the current cluster, skip this step.

    kinit MRS cluster user

    Example: kinit admin

  8. Run the following command to copy the sample program in the OBS bucket to the Master node in the cluster:

    hadoop fs -Dfs.s3a.access.key=AK -Dfs.s3a.secret.key=SK -copyToLocal source_path.jar target_path.jar

    Example: hadoop fs -Dfs.s3a.access.key=XXXX -Dfs.s3a.secret.key=XXXX -copyToLocal "s3a://mrs-word/program/hadoop-mapreduce-examples-XXX.jar" "/home/omm/hadoop-mapreduce-examples-XXX.jar"

    You can log in to OBS Console using AK/SK. To obtain AK/SK information, click the username in the upper right corner of the management console and choose My Credentials > Access Keys.

  9. Run the following command to submit a wordcount job. If data needs to be read from OBS or outputted to OBS, the AK/SK parameters need to be added.

    source /opt/client/bigdata_env;hadoop jar execute_jar wordcount input_path output_path

    Example: source /opt/client/bigdata_env;hadoop jar /home/omm/hadoop-mapreduce-examples-XXX.jar wordcount -Dfs.s3a.access.key=XXXX -Dfs.s3a.secret.key=XXXX "s3a://mrs-word/input/*" "s3a://mrs-word/output/"

    In the preceding command, input_path indicates a path for storing job input files on OBS. output_path indicates a path for storing job output files on OBS and needs to be set to a directory that does not exist

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