Poll for Job Status (Lambda, Amazon Batch) - Amazon Step Functions
Step 1: Create the state machine and provision resourcesStep 2: Run the state machineExample State Machine Code
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Poll for Job Status (Lambda, Amazon Batch)

This sample project creates an Amazon Batch job poller. It implements an Amazon Step Functions state machine that uses Amazon Lambda to create a Wait state loop that checks on an Amazon Batch job.

This sample project creates and configures all resources so that your Step Functions workflow will submit an Amazon Batch job, and will wait for that job to complete before ending successfully.

Note

You can also implement this pattern without using a Lambda function. For information about controlling Amazon Batch directly, see Using Amazon Step Functions with other services.

This sample project creates the state machine, two Lambda functions, and an Amazon Batch queue, and configures the related IAM permissions.

For more information about how Amazon Step Functions can control other Amazon services, see Using Amazon Step Functions with other services.

Step 1: Create the state machine and provision resources

  1. Open the Step Functions console and choose Create state machine.

  2. Type Job Poller in the search box, and then choose Job Poller from the search results that are returned.

  3. Choose Next to continue.

  4. Step Functions lists the Amazon Web Services used in the sample project you selected. It also shows a workflow graph for the sample project. Deploy this project to your Amazon Web Services account or use it as a starting point for building your own projects. Based on how you want to proceed, choose Run a demo or Build on it.

    This sample project deploys the following resources:

    • Three Lambda functions to submit an Amazon Batch job, get the current status of the submitted Amazon Batch job, and the final job completion status.

    • An Amazon Batch job

    • An Amazon Step Functions state machine

    • Related Amazon Identity and Access Management (IAM) roles

    The following image shows the workflow graph for the Job Poller sample project:

    Workflow graph of the Job Poller sample project.

  5. Choose Use template to continue with your selection.

  6. Do one of the following:

    • If you selected Build on it, Step Functions creates the workflow prototype for the sample project you selected. Step Functions doesn't deploy the resources listed in the workflow definition.

      In Workflow Studio's Design mode, drag and drop states from the States browser to continue building your workflow protoype. Or switch to the Code mode that provides an integrated code editor similar to VS Code for updating the Amazon States Language (ASL) definition of your state machine within the Step Functions console. For more information about using Workflow Studio to build your state machines, see Using Workflow Studio.

      Important

      Remember to update the placeholder Amazon Resource Name (ARN) for the resources used in the sample project before you run your workflow.

    • If you selected Run a demo, Step Functions creates a read-only sample project which uses an Amazon CloudFormation template to deploy the Amazon resources listed in that template to your Amazon Web Services account.

      Tip

      To view the state machine definition of the sample project, choose Code.

      When you're ready, choose Deploy and run to deploy the sample project and create the resources.

      It can take up to 10 minutes for these resources and related IAM permissions to be created. While your resources are being deployed, you can open the CloudFormation Stack ID link to see which resources are being provisioned.

      After all the resources in the sample project are created, you can see the new sample project listed on the State machines page.

      Important

      Standard charges may apply for each service used in the CloudFormation template.

Step 2: Run the state machine

After all the resources are provisioned and deployed, the Start execution dialog box is displayed with example input similar to the following.

{
    "jobName": "my-job",
    "jobDefinition": "arn:aws-cn:batch:us-west-2:123456789012:job-definition/SampleJobDefinition-343f54b445d5312:1",
    "jobQueue": "arn:aws-cn:batch:us-west-2:123456789012:job-queue/SampleJobQueue-4d9d696031e1449",
    "wait_time": 60
  }
Note

wait_time instructs the Wait state to loop every 60 seconds.

  • In the Start execution dialog box, do the following:

    1. (Optional) To identify your execution, you can specify a name for it in the Name box. By default, Step Functions generates a unique execution name automatically.

      Note

      Step Functions allows you to create names for state machines, executions, and activities, and labels that contain non-ASCII characters. These non-ASCII names don't work with Amazon CloudWatch. To ensure that you can track CloudWatch metrics, choose a name that uses only ASCII characters.

    2. (Optional) In the Input box, enter input values in JSON format to run your workflow.

      If you chose to Run a demo, you need not provide any execution input.

      Note

      If the demo project you deployed contains prepopulated execution input data, use that input to run the state machine.

    3. Choose Start execution.

    4. The Step Functions console directs you to a page that's titled with your execution ID. This page is known as the Execution Details page. On this page, you can review the execution results as the execution progresses or after it's complete.

      To review the execution results, choose individual states on the Graph view, and then choose the individual tabs on the Step details pane to view each state's details including input, output, and definition respectively. For details about the execution information you can view on the Execution Details page, see Execution Details page – Interface overview.

    For example, to view the changing status of your Amazon Batch job and the looping results of your execution, choose the Output tab.

    The following image shows the execution status graph in the Graph view. It also shows the execution output for the selected step in the Output tab.

    Execution output for the selected step named Get Final Job Status in the Graoh view.

Example State Machine Code

The state machine in this sample project integrates with Amazon Lambda to submit an Amazon Batch job. Browse through this example state machine to see how Step Functions controls Lambda and Amazon Batch.

For more information about how Amazon Step Functions can control other Amazon services, see Using Amazon Step Functions with other services.

{
    "Comment": "An example of the Amazon States Language that runs an Amazon Batch job and monitors the job until it completes.",
    "StartAt": "Submit Job",
    "States": {
      "Submit Job": {
        "Type": "Task",
        "Resource": "arn:aws-cn:lambda:us-east-1:111122223333:function:StepFunctionsSample-JobStatusPol-SubmitJobFunction-jDaYcl4cx55r",
        "ResultPath": "$.guid",
        "Next": "Wait X Seconds"
      },
      "Wait X Seconds": {
        "Type": "Wait",
        "SecondsPath": "$.wait_time",
        "Next": "Get Job Status"
      },
      "Get Job Status": {
        "Type": "Task",
        "Resource": "arn:aws-cn:lambda:us-east-1:111122223333:function:StepFunctionsSample-JobStatusPoll-CheckJobFunction-1JkJwY10vonI",
        "Next": "Job Complete?",
        "InputPath": "$.guid",
        "ResultPath": "$.status"
      },
      "Job Complete?": {
        "Type": "Choice",
        "Choices": [
          {
            "Variable": "$.status",
            "StringEquals": "FAILED",
            "Next": "Job Failed"
          },
          {
            "Variable": "$.status",
            "StringEquals": "SUCCEEDED",
            "Next": "Get Final Job Status"
          }
        ],
        "Default": "Wait X Seconds"
      },
      "Job Failed": {
        "Type": "Fail",
        "Cause": "Amazon Batch Job Failed",
        "Error": "DescribeJob returned FAILED"
      },
      "Get Final Job Status": {
        "Type": "Task",
        "Resource": "arn:aws-cn::lambda:us-east-1:111122223333:function:StepFunctionsSample-JobStatusPoll-CheckJobFunction-1JkJwY10vonI",
        "InputPath": "$.guid",
        "End": true
      }
    }
  }