Creating an Activity state machine using Step Functions

In the Step Functions console, in the navigation pane on the left, choose Activities.

Choose Create activity.

Enter a Name for the activity, for example, get-greeting, and then choose Create activity.

When your activity task is created, make a note of its ARN, as shown in the following example.

arn:aws-cn:states:us-east-1:123456789012:activity:get-greeting

In the Step Functions console, in the navigation pane on the left, choose State machines.

On the State machines page, choose Create state machine.

In the Choose a template dialog box, select Blank.

Choose Select to open Workflow Studio in Design mode.

For this tutorial, you'll write the Amazon States Language (ASL) definition of your state machine in the code editor. To do this, choose Code.

Remove the existing boilerplate code and paste the following code. Remember to replace the example ARN in the Resource field with the ARN of the activity task that you created earlier in Step 1: Create an Activity.

{
  "Comment": "An example using a Task state.",
  "StartAt": "getGreeting",
  "Version": "1.0",
  "TimeoutSeconds": 300,
  "States":
  {
    "getGreeting": {
      "Type": "Task",
      "Resource": "arn:aws-cn:states:us-east-1:123456789012:activity:get-greeting",
      "End": true
    }
  }
}

This is a description of your state machine using the Amazon States Language (ASL). It defines a single Task state named getGreeting. For more information, see State Machine Structure.

On the Graph visualization, make sure the workflow graph for the ASL definition you added looks similar to the following graph.

Specify a name for your state machine. To do this, choose the edit icon next to the default state machine name of MyStateMachine. Then, in State machine configuration, specify a name in the State machine name box.

For this tutorial, enter the name ActivityStateMachine.

(Optional) In State machine configuration, specify other workflow settings, such as state machine type and its execution role.

For this tutorial, keep all the default selections in State machine settings.

If you've previously created an IAM role with the correct permissions for your state machine and want to use it, in Permissions, select Choose an existing role, and then select a role from the list. Or select Enter a role ARN and then provide an ARN for that IAM role.

In the Confirm role creation dialog box, choose Confirm to continue.

You can also choose View role settings to go back to State machine configuration.

Create a file named GreeterActivities.java.

Add the following code to it.

import com.amazonaws.ClientConfiguration;
import com.amazonaws.auth.EnvironmentVariableCredentialsProvider;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.stepfunctions.AWSStepFunctions;
import com.amazonaws.services.stepfunctions.AWSStepFunctionsClientBuilder;
import com.amazonaws.services.stepfunctions.model.GetActivityTaskRequest;
import com.amazonaws.services.stepfunctions.model.GetActivityTaskResult;
import com.amazonaws.services.stepfunctions.model.SendTaskFailureRequest;
import com.amazonaws.services.stepfunctions.model.SendTaskSuccessRequest;
import com.amazonaws.util.json.Jackson;
import com.fasterxml.jackson.databind.JsonNode;
import java.util.concurrent.TimeUnit;


public class GreeterActivities {

    public String getGreeting(String who) throws Exception {
        return "{\"Hello\": \"" + who + "\"}";
    }

    public static void main(final String[] args) throws Exception {
        GreeterActivities greeterActivities = new GreeterActivities();
        ClientConfiguration clientConfiguration = new ClientConfiguration();
        clientConfiguration.setSocketTimeout((int)TimeUnit.SECONDS.toMillis(70));

        AWSStepFunctions client = AWSStepFunctionsClientBuilder.standard()
                .withRegion(Regions.US_EAST_1)
                .withCredentials(new EnvironmentVariableCredentialsProvider())
                .withClientConfiguration(clientConfiguration)
                .build();

        while (true) {
            GetActivityTaskResult getActivityTaskResult =
                    client.getActivityTask(
                            new GetActivityTaskRequest().withActivityArn(ACTIVITY_ARN));

            if (getActivityTaskResult.getTaskToken() != null) {
                try {
                    JsonNode json = Jackson.jsonNodeOf(getActivityTaskResult.getInput());
                    String greetingResult =
                            greeterActivities.getGreeting(json.get("who").textValue());
                    client.sendTaskSuccess(
                            new SendTaskSuccessRequest().withOutput(
                                    greetingResult).withTaskToken(getActivityTaskResult.getTaskToken()));
                } catch (Exception e) {
                    client.sendTaskFailure(new SendTaskFailureRequest().withTaskToken(
                            getActivityTaskResult.getTaskToken()));
                }
            } else {
                Thread.sleep(1000);
            }
        }
    }
}

In the parameter list of the GetActivityTaskRequest().withActivityArn() constructor, replace the ACTIVITY_ARN value with the ARN of the activity task that you created earlier in Step 1: Create an Activity.

On the ActivityStateMachine page, choose Start execution.

The Start execution dialog box is displayed.

In the Start execution dialog box, do the following:

1. (Optional) Enter a custom execution name to override the generated default.

   Non-ASCII names and logging

   Step Functions accepts names for state machines, executions, activities, and labels that contain non-ASCII characters. Because such characters will not work with Amazon CloudWatch, we recommend using only ASCII characters so you can track metrics in CloudWatch.

2. In the Input box, enter the following JSON input to run your workflow.

   {
     "who": "Amazon Step Functions"
   }

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 overview.

On the command line, navigate to the directory in which you created GreeterActivities.java.

To use the Amazon SDK, add the full path of the lib and third-party directories to the dependencies of your build file and to your Java CLASSPATH. For more information, see Downloading and Extracting the SDK in the Amazon SDK for Java Developer Guide.

Compile the file.

$ javac GreeterActivities.java

Run the file.

$ java GreeterActivities

On the Step Functions console, navigate to the Execution Details page.

When the execution completes, examine the results of your execution.

Stop the worker.