Helper functions for interpreting fargo errors

errors.go

package fargo

import (
	"net/http"

	"github.com/hudl/fargo"
)

// errorBoreHTTPStatusCode returns true if the supplied error originated from an HTTP response
// bearing the given HTTP status code.
func errorBoreHTTPStatusCode(err error, code int) bool {
	c, ok := fargo.HTTPResponseStatusCode(err)
	return ok && c == code
}

// eurekaThoughtInstanceWasInvalid returns true if the error arose during an instance registration
// attempt due to Eureka rejecting the proposed instance as invalid.
func eurekaThoughtInstanceWasInvalid(err error) bool {
	return errorBoreHTTPStatusCode(err, http.StatusBadRequest)
}

// instanceWasMissing returns true if the error arose during an instance retrieval, status update,
// lease renewal, or deregistration attempt due to the target instance not being registered, being
// unknown to Eureka.
//
// See instanceWasMissingForMetadataUpdate to assess failures arising during metadata update attempts.
func instanceWasMissing(err error) bool {
	return errorBoreHTTPStatusCode(err, http.StatusNotFound)
}

// instanceWasMissingForMetadataUpdate returns true if the error arose during a metadata update
// attempt due to the target instance not being registered, being unknown to Eureka.
//
// See instanceWasMissing to assess failures arising during instance retrieval, status update,
// lease renewal, or deregistration attempts.
func instanceWasMissingForMetadataUpdate(err error) bool {
	return errorBoreHTTPStatusCode(err, http.StatusInternalServerError)
}

These functions are a caller-side adaptation of an earlier proposal for the fargo library itself (hudl/fargo#47), part of which made it into hudl/fargo#52.