Tutorial: Learn to use the AWS Step Functions Workflow Studio - AWS Step Functions

Tutorial: Learn to use the AWS Step Functions Workflow Studio

In this tutorial, you will learn the basics of working with Workflow Studio for AWS Step Functions. In Workflow Studio, you'll create a state machine containing multiple states, including Pass, Choice, Fail, Wait, and Parallel. You'll use the drag and drop feature to search for, select, and configure these states. Then, you'll view the auto-generated Amazon States Language JSON code for your workflow, exit Workflow Studio, run the state machine, and review the execution details.

In this tutorial, you'll also learn how to update the state machine and view the changes in the execution output. Finally, you'll perform a clean-up step and delete your state machine.

After you complete this tutorial, you'll know how to use Workflow Studio to create and configure a workflow. You'll also know how to update, execute, and delete your state machine.

Note

Before you start, make sure to complete the prerequisites for this tutorial.

Step 1: Navigate to Workflow Studio

  1. Sign in to the Step Functions console.

  2. Choose Create state machine.

  3. On the Choose authoring method page, choose Design your workflow visually.

  4. For Type, keep the default selection of Standard.

    Step Functions has two workflow types: Standard and Express. These types determine how Step Functions performs tasks, integrates with AWS services, and manages pricing. Once you create a state machine, you can't change its workflow type.

    For a side-by-side comparison of both workflows, under Type, choose Help me decide.

  5. Choose Next. This will open Workflow Studio.

    
            Workflow Studio interface. The Actions panel on the left is
              selected.

Step 2: Create a state machine

In Workflow Studio, a state machine is a graphical representation of your workflow. You can use Workflow Studio to define, configure, and examine the individual steps of your workflow.

To create a state machine

  1. In Workflow Studio, from the states browser on the left, choose the Flow panel. Then, drag a Pass state to the empty state labelled Drag first state here.

  2. Drag a Choice state from the Flow panel and drop it below the Pass state.

  3. For State name, replace the default name. For this tutorial, use the name IsHelloWorldExample.

  4. Drag another Pass state and drop it to one branch of the Choice state. Then, drag a Fail state to the other branch of the Choice state.

  5. Choose the Pass (1) state, and rename it to Yes. Rename the Fail state as No.

  6. Specify the Choice state's branching logic using the boolean variable IsHelloWorldExample.

    If IsHelloWorldExample is False, the workflow will enter the No state. Otherwise, the workflow will continue its execution flow in the Yes state's branch.

    To define the branching logic, do the following:

    1. Choose the Choice state on the canvas, and then under Choice Rules choose 
                  edit Choice Rule
                in the Rule #1 box to define the first choice rule.

    2. Choose Add conditions.

    3. In the Conditions for rule #1 dialog box, enter $.IsHelloWorldExample under Variable.

    4. Choose is equal to under Operator.

    5. Choose Boolean constant under Value, and then choose true from the dropdown list.

    6. Choose Save conditions.

    7. Make sure the Then next state is: dropdown list has Yes selected.

    8. Choose Add new choice rule, then choose Add conditions. In the Rule #2 box, define the second choice rule when the IsHelloWorldExample variable's value is false by repeating substeps 6.c through 6.e. For step 6.e, choose false instead of true.

    9. In the Rule #2 box, choose No from the Then next state is: dropdown list.

    10. In the Default rule box, click 
                  edit
                    Choice
                    Rule
                to define the default choice rule, and then choose Yes from the dropdown list.

  7. Add a Wait state after the Yes Pass state, and name it Wait 3 sec. Then, configure the wait time to be three seconds by doing the following steps:

    1. Under Options, keep the default selection of Wait for a fixed interval.

    2. Under Seconds, make sure Enter seconds is selected, and then enter 3 in the box.

  8. After the Wait 3 sec state, add a Parallel state. Add two more Pass states in its two branches. Name the first Pass state Hello. Name the second Pass state World.

    The completed workflow will look like this:

    
            The completed workflow for the IsHelloWorldExample state
              machine.

Step 3: Review the auto-generated Amazon States Language definition

As you drag and drop states from the Flow panel onto the canvas, Workflow Studio automatically composes the Amazon States Language definition of your workflow in real-time. You can edit this definition as required.

  1. (Optional) Choose Definition on the Inspector panel and view the state machine's workflow.

    The following example code shows the auto-generated Amazon States Language definition for the IsHelloWorldExample state machine. The Choice state that you added in Workflow Studio is used to determine the execution flow based on the branching logic you defined in Step 2.

    { "Comment": "A Hello World example of the Amazon States Language using Pass states", "StartAt": "Pass", "States": { "Pass": { "Type": "Pass", "Next": "IsHelloWorldExample", "Comment": "A Pass state passes its input to its output, without performing work. Pass states are useful when constructing and debugging state machines." }, "IsHelloWorldExample": { "Type": "Choice", "Comment": "A Choice state adds branching logic to a state machine. Choice rules can implement 16 different comparison operators, and can be combined using And, Or, and Not\"", "Choices": [ { "Variable": "$.IsHelloWorldExample", "BooleanEquals": false, "Next": "No" }, { "Variable": "$.IsHelloWorldExample", "BooleanEquals": true, "Next": "Yes" } ], "Default": "Yes" }, "No": { "Type": "Fail", "Cause": "Not Hello World" }, "Yes": { "Type": "Pass", "Next": "Wait 3 sec" }, "Wait 3 sec": { "Type": "Wait", "Seconds": 3, "Next": "Parallel" }, "Parallel": { "Type": "Parallel", "End": true, "Branches": [ { "StartAt": "Hello", "States": { "Hello": { "Type": "Pass", "End": true } } }, { "StartAt": "World", "States": { "World": { "Type": "Pass", "End": true } } } ] } } }
  2. Choose Next.

  3. On the Review generated code page, review your state machine's Amazon States Language definition. If needed, you can make additional changes under Definition.

  4. Choose Next.

  5. Enter a name for your workflow. For example, enter HelloWorld.

  6. Under Permissions, choose Create a new IAM role.

    When you create a state machine, you select an IAM role that defines which resources the state machine has permission to access during its execution. Choose one of the following options:

    • Create a new IAM role – Select this option when you want Step Functions to create a new IAM role for you based on the definition of your state machine and its configuration details.

    • Choose an existing role – Select this option if you previously created an IAM role for Step Functions and your state machine has the correct permissions.

    • Enter a role ARN – Select this option if you know the ARN for the IAM role that you want to use for Step Functions.

  7. Choose Create state machine.

Step 4: Start a new execution

State machine executions are instances where you run your workflow to perform tasks.

  1. On the HelloWorld page, choose Start execution.

  2. (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.

  3. In the execution Input area, enter input values for your execution in JSON format. Based on your input, the IsHelloWorldExample variable determines which state machine flow will be executed. For now, use the following input value:

    { "IsHelloWorldExample": true }
    Note

    While specifying an execution input is optional, in this tutorial, it is mandatory to specify an execution input similar to the above example input. This input value is referenced in the Choice state when you run the state machine.

  4. Choose Start execution.

  5. The Step Functions console directs you to a page that's titled with your execution ID. On this page, you can review the results of your new execution. Under Details, you can see your execution ARN and a status which indicates if your execution succeeded. You can also see the timestamps for when your execution started and ended. To view the results of your execution, choose Execution output. For this tutorial, if you entered an input value of "IsHelloWorldExample": true, you should see the following output:

    { "IsHelloWorldExample": true }, { "IsHelloWorldExample": true }

Step 5: Update your state machine

When you update a state machine, your updates are eventually consistent. After a short amount of time, all newly started executions will reflect your state machine's updated definition and roleARN. All currently running executions will run to completion under the previous definition and roleARN before they update.

In this step, you'll update your state machine by adding a Result field in the Pass state named World.

  1. On the page titled with your execution ID, choose Edit state machine.

  2. On the Edit HelloWorld page, in the Definition area, choose Workflow Studio.

  3. Choose the Pass state named World on the canvas, and then choose Output.

  4. In the Result box, enter "World has been updated!".

  5. Choose Apply and exit to save the change and return to the Edit HelloWorld page.

  6. (Optional) In the Definition area, view the updated Amazon States Language definition of your workflow.

    { "Type": "Parallel", "End": true, "Branches": [ { "StartAt": "Hello", "States": { "Hello": { "Type": "Pass", "End": true } } }, { "StartAt": "World", "States": { "World": { "Type": "Pass", "Result": "World has been updated!", "End": true } } } ] }
  7. Choose Save, and then choose Start execution.

  8. The Step Functions console displays the following message:

    The changes to your state machine may affect which resources it needs to access. To ensure your state machine has the right permissions, you might need to edit the current IAM role, create a new one, or select a different role.

    This message is standard. Choose Save anyway.

  9. Choose Start execution. In the Start execution dialog box, identify your execution, and then enter the following input value in the Input area:

    { "IsHelloWorldExample": true }
  10. Choose Start Execution again.

  11. (Optional) In the visual workflow panel, choose each step to view its details, input, and output under the Details, Step input and Step output tabs, respectively. For example, in the visual workflow panel, choose the World step, and then choose Step output. The output is World has been updated!

  12. (Optional) To export the graph of your workflow to an SVG or PNG file, choose Export.

Step 6: Clean up

To delete your state machine

  1. From the navigation menu, choose State machines.

  2. On the State machines page, select HelloWorld, and then choose Delete.

  3. The Step Functions console prompts you with the following message:

    You are about to delete your state machine. Do you want to proceed?

    This message is standard. Choose Delete state machine.

    If deletion is successful, a green status bar appears at the top of your screen. The green status bar tells you that your state machine is marked for deletion. Your state machine will be removed when all of its executions stop running.

To delete your execution role

  1. Open the Roles page for IAM.

  2. Choose the IAM role that Step Functions created for you: StepFunctions-HelloWorld-role-EXAMPLE.

  3. Choose Delete role.

  4. Choose Yes, delete.