eoinsha / step-function-api-example

Example Express Step Function behind a REST API in API Gateway

Step Function Express API Example

This is a simple Step Function (EXPRESS) implementation of an AWS API Gateway REST API. It uses CDK to construct a sample state machine that is invoked by an API Gateway Proxy Integration.

Step Function Design

The state machine invokes an HTTPS endpoint using an HTTP Task defined by an EventBridge HTTP Connection. A choice state allows the HTTP invocation to be skipped if the skip=true query string is provided in the URL.

Deployment

npm install
cdk deploy

The API Gateway HTTPS endpoint is printed to the screen on successful deployment.

Evaluating

X-Ray tracing is enabled for the API deployment and the Step Function, allowing you to see errors and performance metrics.

Execute the API as follows (using cURL):

curl -v https://<REPLACE_WITH_YOURAPI_ID>.execute-api.eu-west-1.amazonaws.com/prod

To skip the API invocation and run the simple Pass and Choice states of the step function, add the skip=true query parameter:

curl -v "https://<REPLACE_WITH_YOURAPI_ID>.execute-api.eu-west-1.amazonaws.com/prod?skip=true"

With the HTTP invocation step, this sample shows 404ms end-to-end with 369ms of that for the HTTP invocation.

Skipping the HTTP invocation step, the following sample shows 98ms end-to-end, with 13ms for the State Machine execution. The rest of the time appears to be in the Step Function service orchestration.

Cleaning up

cdk destroy