Testing state machines locally with Step Functions Local

To Nha Notes | Oct. 10, 2023, 3:24 p.m.

Step Functions local

AWS Step Functions Local is a downloadable version of Step Functions that lets you develop and test applications using a version of Step Functions running in your own development environment. The local version of Step Functions can invoke AWS Lambda functions, both in AWS and while running locally. 

Benefits of using Step Functions local

The new Step Functions local Docker image enables you to get started with Step Functions local quickly by using a docker image with all the dependencies. The new Docker image also enables you to include Step Functions local in your containerized builds and as part of your continuous integration testing.

There are no state transition costs with Step Functions local.

The following topics describe how you can set up Step Functions Local using Docker and JAR file, and run Step Functions Local to work with AWS Lambda, AWS Serverless Application Model(AWS SAM) CLI Local, or other supported services.

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Sample projects for Step Functions

PDFRSS

In the AWS Step Functions console, you can choose one of the following starter templates to deploy state machines to your AWS accounts. These starter templates are ready-to-run sample projects that automatically create the workflow proptotype and definition, and all related AWS resources for the project.

You can use these sample projects to deploy and run them as is, or use the workflow prototypes to build on them. If you build upon these projects, Step Functions creates the workflow prototype, but doesn't deploy the resources listed in the workflow definition.

When you deploy the sample projects, they provision a fully functional state machine, and create the related resources for the state machine to run. When you create a sample project, Step Functions uses AWS CloudFormation to create the related resources referenced by the state machine.

Common State Fields

  • InputPath (Optional) – Holds a JSON path to select a portion of the state’s input for task processing. Default value is $, which means the entire input is used by the task.

  • OutputPath (Optional) – A JSON path to specify a portion of the input that should be passed to the output. Default value is $, so the entire input is passed on to the output of the state.

Pass State

  • Result – Used to specify the output of the Pass state to be passed to the next state. It is often used in conjunction with the ResultPath field.

  • ResultSelector

    Use the ResultSelector field to manipulate a state's result before ResultPath is applied. The ResultSelector field lets you create a collection of key value pairs, where the values are static or selected from the state's result. Using the ResultSelector field, you can choose what parts of a state's result you want to pass to the ResultPath field.

  • ResultPath – This is used to merge the input of the state with the values provided in the Result field.

  • Parameters – Create a key-value pair that will be passed as input. We can either use constants, or it can be picked from the input of the state.

InputPath, ResultPath, and OutputPath Examples

Get a Token from the Context Object

The context object is an internal JSON object that contains information about your execution. Like state input, it can be accessed with a path from the"Parameters" field during an execution. When accessed from within a task definition, it includes information about the specific execution, including the task token.  

{ "Execution": { "Id": "arn:aws:states:us-east-1:123456789012:execution:stateMachineName:executionName", "Input": { "key": "value" }, "Name": "executionName", "RoleArn": "arn:aws:iam::123456789012:role...", "StartTime": "2019-03-26T20:14:13.192Z" }, "State": { "EnteredTime": "2019-03-26T20:14:13.192Z", "Name": "Test", "RetryCount": 3 }, "StateMachine": { "Id": "arn:aws:states:us-east-1:123456789012:stateMachine:stateMachineName", "Name": "name" }, "Task": { "Token": "h7XRiCdLtd/83p1E0dMccoxlzFhglsdkzpK9mBVKZsp7d9yrT1W" } }

You can access the task token by using a special path from inside the "Parameters" field of your task definition. To access the input or the context object, you first specify that the parameter will be a path by appending a .$ to the parameter name. The following specifies nodes from both the input and the context object in a "Parameters"specification.

"Parameters": { "Input.$": "$", "TaskToken.$": "$$.Task.Token" },

In both cases, appending .$ to the parameter name tells Step Functions to expect a path. In the first case, "$" is a path that includes the entire input. In the second case, $$. specifies that the path will access the context object, and $$.Task.Tokensets the parameter to the value of the task token in the context object of a running execution.

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Tutorials for Step Functions

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Reference

https://docs.aws.amazon.com/step-functions/latest/dg/sfn-local.html

https://hub.docker.com/r/amazon/aws-stepfunctions-local

https://docs.aws.amazon.com/step-functions/latest/dg/create-sample-projects.html

https://docs.aws.amazon.com/step-functions/latest/dg/tutorials.htmlhtml

https://docs.aws.amazon.com/step-functions/latest/dg/concepts-access-cross-acct-resources.html

https://docs.aws.amazon.com/step-functions/latest/dg/tutorial-access-cross-acct-resources.html#tutorial-access-cross-acct-resources-update-task-def

https://docs.aws.amazon.com/step-functions/latest/dg/connect-supported-services.html

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