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.

   

   • In MRS 1.7.2 or earlier, 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 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.
   • Configure MapReduce job information by referring to Table 1if the cluster version is MRS 1.9.2 or later.
   • Configure MapReduce job information by referring to Table 3 if the cluster version is earlier than MRS 1.9.2.

   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 ;|&><'$. The parameter value cannot be empty or full of spaces. The path of the program to be executed can be stored in HDFS or OBS. The path varies depending on the file system. OBS: The path must start with obs://. Example: obs://wordcount/program/xxx.jar HDFS: The path must start with /user. For details about how to import data to HDFS, see Importing Data. For SparkScript and HiveScript, the path must end with .sql. For MapReduce, the path must end with .jar. For Flink and SparkSubmit, the path must end with .jar or .py. The .sql, .jar, and .py are case-insensitive.
   Parameters	(Optional) It is the key parameter for program execution. Multiple parameters are separated by space. Configuration method: Program class name Data input path Data output path Program class name: It is specified by a function in your program. MRS is responsible for transferring parameters only. Data input path: Click HDFS or OBS to select a path or manually enter a correct path. Data output path: Enter a directory that does not exist. The parameter contains a maximum of 150,000 characters. It cannot contain special characters ;|&><'$, 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.	-

   Table 3 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 ;|&><'$. The parameter value cannot be empty or full of spaces. The path of the program to be executed can be stored in HDFS or OBS. The path varies depending on the file system. OBS: The path must start with s3a://. Example: s3a://wordcount/program/xxx.jar HDFS: The path must start with /user. For details about how to import data to HDFS, see Importing Data. For SparkScript, the path must end with .sql. For MapReduce and Spark, the path must end with .jar. The .sql and .jar are case-insensitive.
   Parameters	Key parameter for program execution. The parameter is specified by the function of the user's program. MRS is only responsible for loading the parameter. Multiple parameters are separated by space. Configuration method: Package name.Class name The parameter contains a maximum of 150,000 characters. It cannot contain special characters ;|&><'$, but 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. For details about how to import data to HDFS, see Importing Data. The parameter contains a maximum of 1,023 characters, excluding special characters such as ;|&>,<'$, and can be left blank.
   Export To	Path for outputting data NOTE: When setting this parameter, select OBS or HDFS. Select a file directory or manually enter a file directory, and click OK. If you add the hadoop-mapreduce-examples-x.x.x.jar sample program or a program similar to hadoop-mapreduce-examples-x.x.x.jar, enter a directory that does not exist. Data can be stored in HDFS or OBS. The path varies depending on the file system. OBS: The path must start with s3a://. (Supported only in MRS 1.8.10 and earlier versions) HDFS: The path must start with /user. The parameter contains a maximum of 1,023 characters, excluding special characters such as ;|&>,<'$, 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

In MRS 3.x and later versions, the default installation path of the client is /opt/Bigdata/client. In MRS 3.x and earlier versions, the default installation path is /opt/client. For details, see the actual situation.

1. Log in to a Master node. For details, see Logging In to an ECS.
2. Run the following command to initialize environment variables:

   source /opt/Bigdata/client/bigdata_env

3. 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

4. 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"

   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.

5. 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