Fix: support HTTPS backend (#33)

* Fix: forwarded request Host has to be overridden with origin request Host

* Add custom host header config when building proxy

config.template.json

@@ -1,6 +1,8 @@
 {
     "main-target": "http://server-mono.localhost",
+    "main-header-host": "server-mono",
     "canary-target": "http://server-micro.localhost",
+    "canary-header-host": "server-micro",
     "sidecar-url": "http://sidecar.localhost",
     "trim-prefix": "/prefix/path/to/strip",
     "circuit-breaker": {

config/config.go

@@ -2,9 +2,11 @@ package config
 
 // Config holds the configuration values to be used throughout the application.
 type Config struct {
-	MainTarget   string `mapstructure:"main-target"`
-	CanaryTarget string `mapstructure:"canary-target"`
-	SidecarURL   string `mapstructure:"sidecar-url"`
+	MainTarget       string `mapstructure:"main-target"`
+	MainHeaderHost   string `mapstructure:"main-header-host"`
+	CanaryTarget     string `mapstructure:"canary-target"`
+	CanaryHeaderHost string `mapstructure:"canary-header-host"`
+	SidecarURL       string `mapstructure:"sidecar-url"`
 
 	// TrimPrefix if set will modify subsequent request path to main, canary, and sidecar service
 	// by removing TrimPrefix substring in the request path string

proxy.go

@@ -23,16 +23,16 @@ type Proxy struct {
 
 // BuildProxies constructs a Proxy object with mainTargetURL as the URL for Main proxy
 // and canaryTargetURL as the URL for Canary proxy
-func BuildProxies(configClient config.HTTPClientConfig, mainTargetURL, canaryTargetURL string) (*Proxy, error) {
+func BuildProxies(configClient config.HTTPClientConfig, mainTargetURL, mainHeaderHost, canaryTargetURL, canaryHeaderHost string) (*Proxy, error) {
 
-	proxyMain, err := newReverseProxy(mainTargetURL)
+	proxyMain, err := newReverseProxy(mainTargetURL, mainHeaderHost)
 	if err != nil {
 		return nil, errors.Trace(err)
 	}
 	proxyMain.Transport = newTransport(configClient.MaxIdleConns, configClient.IdleConnTimeout, configClient.DisableCompression, configClient.TLS)
 	proxyMain.ErrorLog = log.New(os.Stderr, "[proxy-main] ", log.LstdFlags|log.Llongfile)
 
-	proxyCanary, err := newReverseProxy(canaryTargetURL)
+	proxyCanary, err := newReverseProxy(canaryTargetURL, canaryHeaderHost)
 	if err != nil {
 		return nil, errors.Trace(err)
 	}
@@ -56,11 +56,23 @@ func newTransport(maxIdleConns, idleConnTimeout int, disableCompression bool, tl
 	}
 }
 
-func newReverseProxy(target string) (*httputil.ReverseProxy, error) {
+func newReverseProxy(target, customHost string) (*httputil.ReverseProxy, error) {
 	url, err := url.ParseRequestURI(target)
 	if err != nil {
 		return nil, errors.Trace(err)
 	}
 
-	return httputil.NewSingleHostReverseProxy(url), nil
+	proxy := httputil.NewSingleHostReverseProxy(url)
+
+	director := proxy.Director
+	proxy.Director = func(req *http.Request) {
+		director(req)
+		if customHost != "" {
+			req.Host = customHost
+		} else {
+			req.Host = req.URL.Host
+		}
+	}
+
+	return proxy, nil
 }

proxy_test.go

@@ -39,7 +39,7 @@ func Test_newReverseProxy(t *testing.T) {
 			t.Run(tc.name, func(t *testing.T) {
 				t.Parallel()
 
-				got, err := newReverseProxy(c.urlTarget)
+				got, err := newReverseProxy(c.urlTarget, "")
 
 				if (err != nil) != c.wantErr {
 					t.Errorf("newReverseProxy() error = %v, wantErr %v", err, c.wantErr)

server/server.go

@@ -43,7 +43,7 @@ type Server struct {
 func NewServer(config config.Config) (*Server, error) {
 	server := &Server{config: config}
 
-	proxies, err := canaryrouter.BuildProxies(config.Client.MainAndCanary, config.MainTarget, config.CanaryTarget)
+	proxies, err := canaryrouter.BuildProxies(config.Client.MainAndCanary, config.MainTarget, config.MainHeaderHost, config.CanaryTarget, config.CanaryHeaderHost)
 	if err != nil {
 		return nil, errors.Trace(err)
 	}