Running a MapReduce Job

Prerequisites

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

Before you upload the program packages and data files to OBS, you need to create an OBS agency and bind it to the MRS cluster. For details, see Configuring a Storage-Compute Decoupled Cluster (Agency).

Submitting a Job on the GUI

1. Log in to the MRS 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 page, click Synchronize on the right side of IAM User Sync to synchronize IAM users. For details, see Synchronizing IAM Users to MRS.

   

   • When the policy of the user group to which the IAM user belongs changes from MRS ReadOnlyAccess to MRS CommonOperations, MRS FullAccess, or MRS Administrator, wait for 5 minutes until the new policy takes effect after the synchronization is complete because the SSSD (System Security Services Daemon) 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 CommonOperations, MRS FullAccess, or MRS Administrator to MRS ReadOnlyAccess, 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.
   

   If the IAM username contains spaces (for example, admin 01), a job cannot be created.

6. In Type, select MapReduce. Configure other job information.

   

   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 ;|&><'$. The parameter value cannot be empty or full of spaces. The path of the program to be executed can be stored in HDFS or OBS. The path varies depending on the file system. OBS: The path must start with obs://. Example: obs://wordcount/program/xxx.jar HDFS: The path must start with /user. For details about how to import data to HDFS, see Importing Data. For SparkScript and HiveScript, the path must end with .sql. For MapReduce, the path must end with .jar. For Flink and SparkSubmit, the path must end with .jar or .py. The .sql, .jar, and .py are case-insensitive.
   Parameters	(Optional) It is the key parameter for program execution. Multiple parameters are separated by space. Configuration method: Program class name Data input path Data output path Program class name: It is specified by a function in your program. MRS is responsible for transferring parameters only. Data input path: Click HDFS or OBS to select a path or manually enter a correct path. Data output path: Enter a directory that does not exist. The parameter contains a maximum of 150,000 characters. It cannot contain special characters ;|&><'$, but can be left blank. CAUTION: If you enter a parameter with sensitive information (such as the login password), the parameter may be exposed in the job details display and log printing. Exercise caution when performing this operation.
   Service Parameter	(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. Table 2 lists the common service configuration parameters.
   Command Reference	Command submitted to the background for execution when a job is submitted.

   Table 2 Service Parameter parameters

   Parameter	Description	Example Value
   fs.obs.access.key	Key ID for accessing OBS.	-
   fs.obs.secret.key	Key corresponding to the key ID for accessing OBS.	-

7. Confirm job configuration information and click OK.

   After the job is created, you can manage it.

Submitting a Job in the Background

The default client installation path for MRS 3.x or later is /opt/Bigdata/client, and for versions earlier than MRS 3.x is /opt/client. Configure the path based on site requirements.

1. Log in to the MRS 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/Bigdata/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 program in the OBS file system to the Master node in the cluster:

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

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

   

   • Commands carrying authentication passwords pose security risks. Disable historical command recording before running such commands to prevent information leakage.
   • You can log in to the 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/Bigdata/client/bigdata_env;hadoop jar execute_jar wordcount input_path output_path

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