Developing a Real-Time Processing Single-Task MRS Flink SQL Job

Prerequisites

• You have created a job by referring to Creating a Job.
• You have locked the job. Otherwise, you must click Lock so that you can develop the job. A job you create or import is locked by you by default. For details, see the lock function.

Developing an SQL Script

1. Log in to the DataArts Studio console by following the instructions in Accessing the DataArts Studio Instance Console.
2. On the DataArts Studio console, locate a workspace and click DataArts Factory.
3. In the left navigation pane of DataArts Factory, choose Development > Develop Job.
4. In the job directory, double-click the name of a single-task job to access the job development page.
5. On the right of the SQL editor, click Basic Info to configure basic information of the job. Table 1 provides the basic information about the single-task MRS Flink SQL job.

   Table 1 Basic job information

   Parameter	Description
   Owner	An owner configured during job creation is automatically matched. This parameter value can be modified.
   Job Agency	This parameter is available when Scheduling Identities is set to Yes. After an agency is configured, the job interacts with other services as an agency during job execution.
   Priority	Priority configured during job creation is automatically matched. This parameter value can be modified.
   Execution Timeout	Timeout of the job instance. If this parameter is set to 0 or is not set, this parameter does not take effect. If the notification function is enabled for the job and the execution time of the job instance exceeds the preset value, the system sends a specified notification, and the job keeps running.
   Exclude Waiting Time from Instance Timeout Duration	Whether to exclude the wait time from the instance execution timeout duration If you select this option, the time to wait before an instance starts running is excluded from the timeout duration. You can modify this setting on the Default Configuration page. If you do not select this option, the time to wait before an instance starts running is included in the timeout duration.
   Custom Parameter	Set the name and value of the parameter.
   Job Tag	Configure job tags to manage jobs by category. Click Add to add a tag to the job. You can also select a tag configured in Managing Job Tags.

   Table 2 Attributes of the real-time processing single-task MRS Flink SQL job

   Property	Description
   Flink SQL properties
   Flink Job Name	Enter the Flink job name. The name is automatically generated in Workspace-Job name format. NOTE: It can contain only letters, digits, hyphens (-), and underscores. A maximum of 64 characters are allowed, and Chinese characters are not allowed.
   MRS Cluster	Select an MRS cluster. NOTE: Currently, jobs with a single Flink SQL node support MRS 3.2.0-LTS.1 and later versions.
   Program Parameter	Set the job running parameters. This parameter is displayed only after an MRS cluster is selected. (Optional) Configure optimization parameters such as threads, memory, and vCPUs for the job to optimize resource usage and improve job execution performance. CAUTION: You can query historical checkpoints and select a specified checkpoint to start a real-time Flink SQL job. To make a Flink checkpoint take effect, configure the following two parameters: Figure 1 Configuring program parameters Checkpoint interval: -yD: execution.checkpointing.interval=1000 Number of reserved checkpoints: -yD: state.checkpoints.num-retained=10 When querying the checkpoint list, enter parameter -s and click the parameter value text box. The parameter value will be automatically displayed. NOTE: This parameter is mandatory if the cluster version is MRS 1.8.7 or later than MRS 2.0.1. Click Select Template and select a parameter template. You can also select multiple templates. For details about how to create templates, see Configuring a Template. For details about the program parameters of MRS Spark jobs, see Running a Flink Job in the MapReduce Service User Guide.
   Flink Job Parameter	Set the parameters for the Flink job. Variables required for executing the Flink job. These variables are specified by the functions in the Hive script. Multiple parameters are separated by spaces.
   MRS Resource Queue	Select a created MRS resource queue. Select a queue you configured in the queue permissions of DataArts Security. If you set multiple resource queues for this node, the resource queue you select here has the highest priority.
   Rerun Policy	Rerun from the previous checkpoint Rerun the job
   Input Data Path	Set the input data path. You can select an HDFS or OBS path.
   Output Data Path	Set the output data path. You can select an HDFS or OBS path.

   Table 3 Advanced Settings

   Parameter	Mandatory	Description
   Job Status Polling Interval (s)	Yes	Set the interval at which the system checks whether the job is complete. The interval can range from 30s to 60s, or 120s, 180s, 240s, or 300s. During job execution, the system checks the job status at the configured interval.
   Maximum Wait Time	Yes	Set the timeout interval for the job. If the job is not complete within the timeout interval and retry is enabled, the job will be executed again. NOTE: If the job is in starting state and fails to start, it will fail upon timeout.
   Retry upon Failure	Yes	Whether to re-execute the job if it fails Yes: The job will be re-executed if it fails. Configure the following parameters: Retry upon Timeout Maximum Retries Retry Interval (seconds) No: The job will not be re-executed if it fails. This is the default setting. NOTE: If retry is configured for a job node and the timeout duration is configured, the system allows you to retry a node when the node execution times out. If a node is not re-executed when it fails upon timeout, you can go to the Default Configuration page to modify this policy. Retry upon Timeout is displayed only when Retry upon Failure is set to Yes.

6. Enter one or more SQL statements in the SQL editor.
   

   • SQL statements are separated by semicolons (;). If semicolons are used in other places but not used to separate SQL statements, escape them with backslashes (\). The following is an example:

     select 1;
     select * from a where b="dsfa\;";  --example 1\;example 2.

   • The script cannot be larger than 16 MB.
   • The system date obtained by using an SQL statement is different from that obtained by using the database tool. The query result is stored in the database in the YYYY-MM-DD format, but the query result displayed on the page is in the converted format.
   • You can click Check Syntax to check the syntax of Flink SQL jobs. Above the editor, click Check Syntax to verify the semantics of SQL statements. After the check is complete, you can view the check result in the lower part of the page.
   • You can control display of the script execution history by setting Script Execution History in Default Configuration to Myself or All users.
   To facilitate script development, DataArts Factory provides the following capabilities:

   • The script editor supports the following shortcut keys, which improve the script development efficiency:
     • F8: Run a script.
     • F9: Stop running a script.
     • Ctrl + /: Comment out or uncomment the line or code block where the cursor resides.
     • Ctrl + Z: Undo an action.
     • Ctrl + F: Search for information.
     • Ctrl + Shift + R: Replace
     • Ctrl + X: Cut
     • Ctrl + S: Save a script.
     • Alt + mouse dragging: Select columns to edit a block.
     • Ctrl + mouse click: Select multiple lines to edit or indent them together.
     • Shift + Ctrl + K: Delete the current line.
     • Ctrl + → (or ←): Move the cursor rightwards (or leftwards) by word.
     • Ctrl + Home or Ctrl + End: Navigate to the beginning or end of the current file.
     • Home or End: Navigate to the beginning or end of the current line.
     • Ctrl + Shift + L: Double-click all the same character strings and add cursors to them to implement batch modification.
     • Ctrl + D: Delete a line.
     • Shift + Ctrl + U: Unlock a script.
     • Ctrl + Alt + K: Select the word where the cursor resides.
     • Ctrl + B: Format
     • Ctrl + Shift + Z: Redo
     • Ctrl + Enter: Execute the selected line or content.
     • Ctrl + Alt + F: Flag
     • Ctrl + Shift + K: Search for the previous one.
     • Ctrl + K: Search for the next one.
     • Ctrl + Backspace: Delete the word to the left of the cursor.
     • Ctrl + Delete: Delete the word to the right of the cursor.
     • Alt + Backspace: Delete all content from the beginning of the line to the cursor.
     • Alt + Delete: Delete all content from the cursor to the end of the line.
     • Alt + Shift-Left: Select all content from the beginning of the line to the cursor.
     • Alt + Shift-Right: Select all content from the cursor to the end of the line.
   • Script parameters

     Enter script parameters in the SQL statement and click Parameter Setup in the right pane of the editor and then click Update from Script. You can also directly configure parameters and constants for the job script.

     In the following script example, str1 indicates the parameter name. It can contain only letters, digits, hyphens (-), underscores (_), greater-than signs (>), and less-than signs (<), and can contain a maximum of 16 characters. The parameter name must be unique.

     select ${str1} from data;

7. (Optional) In the upper part of the editor, click Format to format SQL statements.
8. Above the editor, click Save to save the job and submit it.

Configuring Job Parameters

Click Parameters on the right of the editor and set the parameters described in Table 4.

Click the Parameter Preview tab and configure the parameters listed in Table 5.

In Parameter Preview, if a job parameter has a syntax error, the system displays a message.

If a parameter depends on the data generated during job execution, such data cannot be simulated and displayed in Parameter Preview.

Saving a Job

After configuring the job, perform the following operations:

1. Click Start to execute the job.
   

   A maximum of 1,000 records can be displayed in the execution result. The size of the execution result cannot exceed 3 MB. If the size exceeds 3 MB, the result will be truncated.

2. After the job is executed, click to save the job configuration.

   After the job is saved, a version is automatically generated and displayed in Versions. The version can be rolled back. If you save a job multiple times within a minute, only one version is recorded. If the intermediate data is important, you can click Save new version to save and add a version.

Templates

When developing a real-time processing, single-task Flink SQL job, you can reference a script template. For details about how to create a template, see Configuring a Template. For details about how to use a script template, see Using Script Templates and Parameter Templates.