serverless-offline-stepfunctions-plugin

serverless-offline-stepfunctions-plugin

Overview

This Serverless Offline plugin provides local support for Serverless Step Functions. It creates state machines for every stepFunctions entry on a local step function emulator.

This plugin doesn't manage the local step function emulator. You need to install and start the emulator before using this plugin.

Tested emulators:

• stepfunctions-local standalone
• stepfunctions-local via serverless-offline-stepfunctions-local plugin

Installation

npm install serverless-offline-stepfunctions-plugin

OR

yarn add serverless-offline-stepfunctions-plugin

Usage

1. Enable this plugin by editing your serverless.yml file and placing an serverless-offline-stepfunctions-plugin entry in the plugins section, placed above the serverless-offline plugin
2. Create a offlineStepFunctions entry in the custom section.
3. For each lambda task, add a task name -> lambda name pair. See serverless.yml example below.
4. (Optional) Add a host and port property defining the emulator host and port. Default host is localhost and default port is 4584.
5. (Optional) Add an accountId property. Default is 0123456789.

Example

serverless.yml:

plugins:
  # Note how this comes before serverless-offline
  - serverless-step-functions
  - serverless-offline-stepfunctions-plugin
  - serverless-offline

functions:
  hello:
    handler: src/hello.default
    
stepFunctions:
  stateMachines:
    Test:
      definition:
        Comment: Test Step Function
        StartAt: HelloWorld
        States:
          HelloWorld:
            Type: Task
            Resource:
              Fn::GetAtt: [HelloLambdaFunction, Arn]
            End: true

custom:
  offlineStepFunctions:
  	accountId: 0123456789
    host: localhost
    port: 4584
    functions:
	    HelloWorld: hello

Execute via AWS CLI

aws stepfunctions --endpoint http://localhost:4584 start-execution --state-machine-arn "arn:aws:states:us-east-1:0123456789:stateMachine:Test" --input '{"first": 1, "second": 2}'

Executing via AWS JS SDK

const AWS = require('aws-sdk');

const stepFunctions = new AWS.StepFunctions({
	endpoint: `http://localhost:4584`,
});

const response = stepFunctions
	.startExecution({
		stateMachineArn: 'arn:aws:states:us-east-1:0123456789:stateMachine:Test',
		input: JSON.stringify({{"first": 1, "second": 2}}),
	})
	.promise();

Comparison to other plugins

serverless-step-functions-offline

This plugin has an internal simulation of the Step Function API. It supports a subset of the API and runs independently of Serverless Offline. Because of this, it cannot support direct API calls from AWS JS SDK or CLI. For example, you cannot start state machine execution from lambda function. You can only start execution from the command line. Furthermore, it only supports NodeJS lambda tasks.

serverless-offline-step-functions

Like the plugin above it (serverless-step-functions-offline), this plugin internally simulates Step Functions. It has no support for AWS JS SDK or CLI and has implemented even less of the Step Functions API.

serverless-step-functions-local

This plugin downloads and wraps AWS's Step Functions Local and creates state machines for each stepFunctions entry. It's the closest to this plugin in terms of functionality. But the one main distinction is that it manages your Step Functions emulator for you, which also means you have to use its emulator. Which means you need Java to download and run Step Functions Local. On the contrary, serverless-offline-stepfunctions-plugin defers that decision and control, so you are free to use whatever emulator you wish.

Roadmap

• Integrate with Step Functions Local
• Integration with Localstack