Poll for Job Status (Lambda, Amazon Batch) - Amazon Step Functions
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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.

Create the State Machine and Provision Resources

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

  2. Choose Run a sample project, and then choose Job Poller.

    The state machine Definition and Visual Workflow are displayed.

    
          Job poller visual workflow
    Note

    The Definition section in this state machine references the Amazon resources that will be created for this sample project.

  3. Choose Next.

    The Deploy resources page is displayed, listing the resources that will be created. For this sample project, the resources include:

    • A SubmitJob Lambda function

    • A CheckJob Lambda function

    • A SampleJobQueue Batch Job Queue

  4. Choose Deploy resources.

    Note

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

Starting an Execution

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-east-1:123456789012:job-definition/SampleJobDefinition-343f54b445d5312:1", "jobQueue": "arn:aws-cn:batch:us-east-1:123456789012:job-queue/SampleJobQueue-4d9d696031e1449", "wait_time": 60 }
Note

wait_time instructs the Wait state to loop every 60 seconds.

To start a new execution

  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 state machine, execution, and activity names 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. Choose Start Execution.

  3. (Optional) After the execution is complete, choose individual states on the Graph inspector, and then choose the Step input and Step output tabs to view each state's input and output respectively.

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

    
              State machine execution.

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 } } }