Expose response HTTP status code in errors

For various operations involving HTTP requests against the Eureka
server, allow callers to interpret surfaced failures by way of
inspecting the HTTP response's status code.

errors.go

@@ -2,6 +2,29 @@ package fargo
 
 // MIT Licensed (see README.md) - Copyright (c) 2013 Hudl <@Hudl>
 
+import (
+	"fmt"
+)
+
+type unsuccessfulHTTPResponse struct {
+	statusCode    int
+	messagePrefix string
+}
+
+func (u *unsuccessfulHTTPResponse) Error() string {
+	return fmt.Sprint(u.messagePrefix, ", rcode = ", u.statusCode)
+}
+
+// HTTPResponseStatusCode extracts the HTTP status code for the response from Eureka that motivated
+// the supplied error, if any. If the returned present value is true, the returned code is an HTTP
+// status code.
+func HTTPResponseStatusCode(err error) (code int, present bool) {
+	if u, ok := err.(*unsuccessfulHTTPResponse); ok {
+		return u.statusCode, true
+	}
+	return 0, false
+}
+
 type AppNotFoundError struct {
 	specific string
 }

errors_test.go

@@ -0,0 +1,34 @@
+package fargo
+
+// MIT Licensed (see README.md) - Copyright (c) 2013 Hudl <@Hudl>
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestHTTPResponseStatusCode(t *testing.T) {
+	tests := []struct {
+		input   error
+		present bool
+		code    int
+	}{
+		{nil, false, 0},
+		{errors.New("other"), false, 0},
+		{&unsuccessfulHTTPResponse{404, "missing"}, true, 404},
+	}
+	for _, test := range tests {
+		code, present := HTTPResponseStatusCode(test.input)
+		if present {
+			if !test.present {
+				t.Errorf("input %v: want absent, got code %d", test.input, code)
+				continue
+			}
+			if code != test.code {
+				t.Errorf("input %v: want %d, got %d", test.input, test.code, code)
+			}
+		} else if test.present {
+			t.Errorf("input %v: want code %d, got absent", test.input, test.code)
+		}
+	}
+}

net.go

@@ -131,7 +131,7 @@ func (e *EurekaConnection) RegisterInstance(ins *Instance) error {
 			ins.Id(), ins.App, err.Error())
 		return err
 	}
-	if rcode == 200 {
+	if rcode == http.StatusOK {
 		log.Noticef("Instance=%s already exists in App=%s, aborting registration", ins.Id(), ins.App)
 		return nil
 	}
@@ -164,7 +164,7 @@ func (e *EurekaConnection) ReregisterInstance(ins *Instance) error {
 	if rcode != 204 {
 		log.Warningf("HTTP returned %d registering Instance=%s App=%s Body=\"%s\"", rcode,
 			ins.Id(), ins.App, string(body))
-		return fmt.Errorf("http returned %d possible failure registering instance\n", rcode)
+		return &unsuccessfulHTTPResponse{rcode, "possible failure registering instance"}
 	}
 
 	// read back our registration to pick up eureka-supplied values
@@ -182,8 +182,8 @@ func (e *EurekaConnection) GetInstance(app, insId string) (*Instance, error) {
 	if err != nil {
 		return nil, err
 	}
-	if rcode != 200 {
-		return nil, fmt.Errorf("Error getting instance, rcode = %d", rcode)
+	if rcode != http.StatusOK {
+		return nil, &unsuccessfulHTTPResponse{rcode, "unable to retrieve instance"}
 	}
 	var ins *Instance
 	if e.UseJson {
@@ -219,9 +219,9 @@ func (e *EurekaConnection) DeregisterInstance(ins *Instance) error {
 	}
 	// Eureka promises to return HTTP status code upon deregistration success, but fargo used to accept status code 204
 	// here instead. Accommodate both for backward compatibility with any fake or proxy Eureka stand-ins.
-	if rcode != 200 && rcode != 204 {
+	if rcode != http.StatusOK && rcode != http.StatusNoContent {
 		log.Warningf("HTTP returned %d deregistering Instance=%s App=%s", rcode, ins.Id(), ins.App)
-		return fmt.Errorf("http returned %d possible failure deregistering instance\n", rcode)
+		return &unsuccessfulHTTPResponse{rcode, "possible failure deregistering instance"}
 	}
 
 	return nil
@@ -243,7 +243,7 @@ func (e EurekaConnection) AddMetadataString(ins *Instance, key, value string) er
 	if rcode < 200 || rcode >= 300 {
 		log.Warningf("HTTP returned %d updating metadata Instance=%s App=%s Body=\"%s\"", rcode,
 			ins.Id(), ins.App, string(body))
-		return fmt.Errorf("http returned %d possible failure updating instance metadata ", rcode)
+		return &unsuccessfulHTTPResponse{rcode, "possible failure updating instance metadata"}
 	}
 	ins.SetMetadataString(key, value)
 	return nil
@@ -265,7 +265,7 @@ func (e EurekaConnection) UpdateInstanceStatus(ins *Instance, status StatusType)
 	if rcode < 200 || rcode >= 300 {
 		log.Warningf("HTTP returned %d updating status Instance=%s App=%s Body=\"%s\"", rcode,
 			ins.Id(), ins.App, string(body))
-		return fmt.Errorf("http returned %d possible failure updating instance status ", rcode)
+		return &unsuccessfulHTTPResponse{rcode, "possible failure updating instance status"}
 	}
 	return nil
 }
@@ -286,9 +286,9 @@ func (e *EurekaConnection) HeartBeatInstance(ins *Instance) error {
 		log.Errorf("Error sending heartbeat for Instance=%s App=%s, error: %s", ins.Id(), ins.App, err.Error())
 		return err
 	}
-	if rcode != 200 {
+	if rcode != http.StatusOK {
 		log.Errorf("Sending heartbeat for Instance=%s App=%s returned code %d", ins.Id(), ins.App, rcode)
-		return fmt.Errorf("heartbeat returned code %d\n", rcode)
+		return &unsuccessfulHTTPResponse{rcode, "heartbeat failed"}
 	}
 	return nil
 }

tests/net_test.go

@@ -3,11 +3,33 @@ package fargo_test
 // MIT Licensed (see README.md) - Copyright (c) 2013 Hudl <@Hudl>
 
 import (
+	"fmt"
+	"net/http"
+	"testing"
+
 	"github.com/hudl/fargo"
 	. "github.com/smartystreets/goconvey/convey"
-	"testing"
 )
 
+func shouldNotBearAnHTTPStatusCode(actual interface{}, expected ...interface{}) string {
+	if code, present := fargo.HTTPResponseStatusCode(actual.(error)); present {
+		return fmt.Sprintf("Expected:	no HTTP status code\nActual: 		%d", code)
+	}
+	return ""
+}
+
+func shouldBearHTTPStatusCode(actual interface{}, expected ...interface{}) string {
+	expectedCode := expected[0]
+	code, present := fargo.HTTPResponseStatusCode(actual.(error))
+	if !present {
+		return fmt.Sprintf("Expected:	%d\nActual:		no HTTP status code", expectedCode)
+	}
+	if code != expectedCode {
+		return fmt.Sprintf("Expected:	%d\nActual:		%d", expectedCode, code)
+	}
+	return ""
+}
+
 func TestConnectionCreation(t *testing.T) {
 	Convey("Pull applications", t, func() {
 		cfg, err := fargo.ReadConfig("./config_sample/local.gcfg")
@@ -64,6 +86,7 @@ func TestRegistration(t *testing.T) {
 			}
 			err := e.HeartBeatInstance(&j)
 			So(err, ShouldNotBeNil)
+			So(err, shouldBearHTTPStatusCode, http.StatusNotFound)
 		})
 		Convey("Register an instance to TESTAPP", t, func() {
 			Convey("Instance registers correctly", func() {
@@ -149,6 +172,7 @@ func DontTestDeregistration(t *testing.T) {
 		Convey("Instance cannot check in", func() {
 			err := e.HeartBeatInstance(&i)
 			So(err, ShouldNotBeNil)
+			So(err, shouldBearHTTPStatusCode, http.StatusNotFound)
 		})
 	})
 }