Gateway never returns 500

[kevburnsjr]

API Requests to rudder-server will only ever return a status code of 200 or 400.

rudder-server/gateway/gateway.go

Lines 323 to 329 in 995e9ca

	if errorMessage != "" {
	logger.Debug(errorMessage)
	http.Error(w, errorMessage, 400)
	} else {
	logger.Debug(respMessage)
	w.Write([]byte(respMessage))
	}

This is problematic for at least 2 reasons

1) Lack of differentiation between 400 and 500 reduces visibility into service operation.

Services should differentiate between client errors and server errors. If the database becomes unavailable, you want the service to return 500 so that your alerting system can page the OPS team.

2) Clients treat 4xx and 5xx differently

Some clients will retry events when they receive a 500 and remove events when they receive a 400.

https://github.com/segmentio/analytics-android/blob/47f7341d81766b1b4a101ef69f491835d11f7532/analytics/src/main/java/com/segment/analytics/SegmentIntegration.java#L386-L394

The service must return 5xx on server error in order to minimize event loss during service outage.

[chandumlg]

Gateway error codes are corrected.