Adding an Event Sink Endpoint

Workflow

Copy this checklist and track your progress:

Creating or modifying a sink endpoint:
- [ ] Step 1: Read local AGENTS.md file
- [ ] Step 2: Define in service.yaml
- [ ] Step 3: Generate Boilerplate Code
- [ ] Step 4: Move Implementation and Test if Renamed
- [ ] Step 5: Implement the Business Logic
- [ ] Step 6: Test the Inbound Event Sink
- [ ] Step 7: Document the Microservice
- [ ] Step 8: Versioning

Step 1: Read local AGENTS.md file

Check for and read a local AGENTS.md file in that microservice's directory. The local AGENTS.md file contains microservice-specific instructions that should take precedence over global instructions.

Step 2: Define in service.yaml

Locate the definition of the outbound event in its source microservice.

Define the inbound event sink in the sinks array in the service.yaml of the microservice.

• The signature of the inbound event sink must be an exact copy of the outbound event of the microservice that's firing it.
• The description should explain what circumstances trigger the event. Copy it from the definition of the outbound event of the microservice that's firing it.
• The source is the package import path to the microservice that's firing the event.

sinks:
  - signature: OnMyNewEvent(primitiveParam string, customParam CustomType) (result string)
    description: OnMyNewEvent does X, Y and Z.
    source: package/path/of/another/microservice

Step 3: Generate Boilerplate Code

If you've made changes to service.yaml, run go generate to generate the boilerplate code.

Step 4: Move Implementation and Test if Renamed

If you made a change to the name of the sink in the signature field, you need to move over its implementation in service.go from under the old name to the new name. Similarly, you'll need to move over the implementation of the tests in service_test.go.

Step 5: Implement the Business Logic

Look for the function declaration in service.go and implement or adjust its logic appropriately.

func (svc *Service) OnMyNewEvent(ctx context.Context, primitiveParam string, customParam CustomType) (result string, err error) {
	// Implement logic here
	return result, err
}

Step 6: Test the Inbound Event Sink

Look for the integration test created in service_test.go for the inbound event sink and implement or adjust it appropriately.

• Follow the pattern recommendation in the code
• Add downstream microservices or their mocks to the testing app

func TestMyservice_OnMyNewEvent(t *testing.T) {
	// Implement testing here
}

Step 7: Document the Microservice

Generate documentation for this microservice that captures its purpose, context, and design rationale. Focus on the reasons behind decisions rather than describing what the code does. Explain design choices, tradeoffs, and the context needed for someone to safely evolve this microservice in the future. Store the result in the microservice's local AGENTS.md file.

Step 8: Versioning

Run go generate to version the code.