Workflows

Experiments with AWS step functions.

Usage

See setup and deployment instructions below.

Workflow calling a lambda

See Workflow Lambda for code. Explanation in blog.

Workflow for idempotent tests

See Workflow Idempotent for code.

After deployment the API endpoints are listed as output like-

Outputs:
WorkflowIdempotentStack.WorkflowIdempotentApiEndpointXXXX = https://$api.execute-api.$region.amazonaws.com/prod/

Stack ARN:
arn:aws:cloudformation:region::stack/WorkflowIdempotentStack/id

Invoke using curl like

curl --request POST \
  --url https://$api.execute-api.$region.amazonaws.com/prod/workflow \
  --header 'Content-Type: application/json' \
  --data '{
	"name": "foo",
	"input": { "data": "value"}
}'

the name is the id to be used for the workflow execution.

Workflow for async token pattern

Workflow Stack implements the callback with token pattern. The flow diagram is shown below.

sequenceDiagram
    participant client
    participant systemGateway
    participant systemLambda
    participant systemStepfn
    participant external

    client->>+systemGateway: POST /tasks
    systemGateway->>+systemLambda: invoke lambda for start
    systemLambda->>systemStepfn: start workflow execution
    activate systemStepfn
    systemStepfn->>systemLambda: $workflow init
    systemLambda->>-systemGateway: $taskId started
    systemGateway->>-client: $taskId started


    systemStepfn->>systemLambda: External service step
    activate systemLambda
    systemLambda->>+external: POST /external { id, resumeToken }
    deactivate systemLambda
    activate external
    external->>+systemGateway: PUT /tasks/$taskId { id, resumeToken, status }
    deactivate external
    activate systemGateway
    systemGateway->>+systemLambda: invoke lambda for update status
    deactivate systemGateway
    systemLambda->>systemStepfn: update workflow
    systemStepfn->>systemLambda: $workflow update
    systemLambda->>-systemGateway: $taskId updated

    systemStepfn->>systemStepfn: workflow complete
    deactivate systemStepfn

After deployment the API endpoints are listed as output like-

Outputs:
WorkflowsStack.ServiceApiEndpointXXXX = https://$api.execute-api.$region.amazonaws.com/prod/
WorkflowsStack.WorkflowApiEndpointYYYY = https://$apiComposite.execute-api.$region.amazonaws.com/prod/

Stack ARN:
arn:aws:cloudformation:region::stack/WorkflowsStack/id

API endpoints

Task	Endpoint sample
Start simple workflow	POST https://$api.execute-api.$region.amazonaws.com/prod/workflows
Get simple workflow results	GET https://$api.execute-api.$region.amazonaws.com/prod/workflows/$workflowId
Start composite workflow	POST https://$apiComposite.execute-api.$region.amazonaws.com/prod/compositeWorkflows
Get composite workflow results	GET https://$apiComposite.execute-api.$region.amazonaws.com/prod/compositeWorkflows/$compositeWorkflowId

Deployment

Tooling setup

This project is based on AWS CDK in typescript. Follow the steps in getting started for-

• aws account setup with credentials
• cdk cli installation (v2)
• cdk bootstrapping

Project commands

Task	Command
install npm packages	npm install
build	npm run build
deploy to aws	cdk deploy -all
destroy app	cdk destroy