Move middleware to interfaces.

This makes separating middlewares from the core api easier.
As an example, the authorization middleware is moved to
it's own package.

Initialize all static middlewares when the server is created, reducing
allocations every time a route is wrapper with the middlewares.

Signed-off-by: David Calavera <david.calavera@gmail.com>

api/server/middleware.go

@@ -2,10 +2,8 @@ package server
 
 import (
 	"github.com/Sirupsen/logrus"
-	"github.com/docker/docker/api"
 	"github.com/docker/docker/api/server/httputils"
 	"github.com/docker/docker/api/server/middleware"
-	"github.com/docker/docker/pkg/authorization"
 )
 
 // handleWithGlobalMiddlwares wraps the handler function for a request with
@@ -14,27 +12,13 @@ import (
 func (s *Server) handleWithGlobalMiddlewares(handler httputils.APIFunc) httputils.APIFunc {
 	next := handler
 
-	handleVersion := middleware.NewVersionMiddleware(s.cfg.Version, api.DefaultVersion, api.MinVersion)
-	next = handleVersion(next)
-
-	if s.cfg.EnableCors {
-		handleCORS := middleware.NewCORSMiddleware(s.cfg.CorsHeaders)
-		next = handleCORS(next)
+	for _, m := range s.middlewares {
+		next = m.WrapHandler(next)
 	}
 
-	handleUserAgent := middleware.NewUserAgentMiddleware(s.cfg.Version)
-	next = handleUserAgent(next)
-
-	// Only want this on debug level
 	if s.cfg.Logging && logrus.GetLevel() == logrus.DebugLevel {
 		next = middleware.DebugRequestMiddleware(next)
 	}
 
-	if len(s.cfg.AuthorizationPluginNames) > 0 {
-		s.authZPlugins = authorization.NewPlugins(s.cfg.AuthorizationPluginNames)
-		handleAuthorization := middleware.NewAuthorizationMiddleware(s.authZPlugins)
-		next = handleAuthorization(next)
-	}
-
 	return next
 }

api/server/middleware/cors.go

@@ -4,30 +4,34 @@ import (
 	"net/http"
 
 	"github.com/Sirupsen/logrus"
-	"github.com/docker/docker/api/server/httputils"
 	"golang.org/x/net/context"
 )
 
-// NewCORSMiddleware creates a new CORS middleware.
-func NewCORSMiddleware(defaultHeaders string) Middleware {
-	return func(handler httputils.APIFunc) httputils.APIFunc {
-		return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
-			// If "api-cors-header" is not given, but "api-enable-cors" is true, we set cors to "*"
-			// otherwise, all head values will be passed to HTTP handler
-			corsHeaders := defaultHeaders
-			if corsHeaders == "" {
-				corsHeaders = "*"
-			}
+// CORSMiddleware injects CORS headers to each request
+// when it's configured.
+type CORSMiddleware struct {
+	defaultHeaders string
+}
 
-			writeCorsHeaders(w, r, corsHeaders)
-			return handler(ctx, w, r, vars)
-		}
-	}
+// NewCORSMiddleware creates a new CORSMiddleware with default headers.
+func NewCORSMiddleware(d string) CORSMiddleware {
+	return CORSMiddleware{defaultHeaders: d}
 }
 
-func writeCorsHeaders(w http.ResponseWriter, r *http.Request, corsHeaders string) {
-	logrus.Debugf("CORS header is enabled and set to: %s", corsHeaders)
-	w.Header().Add("Access-Control-Allow-Origin", corsHeaders)
-	w.Header().Add("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, X-Registry-Auth")
-	w.Header().Add("Access-Control-Allow-Methods", "HEAD, GET, POST, DELETE, PUT, OPTIONS")
+// WrapHandler returns a new handler function wrapping the previous one in the request chain.
+func (c CORSMiddleware) WrapHandler(handler func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+		// If "api-cors-header" is not given, but "api-enable-cors" is true, we set cors to "*"
+		// otherwise, all head values will be passed to HTTP handler
+		corsHeaders := c.defaultHeaders
+		if corsHeaders == "" {
+			corsHeaders = "*"
+		}
+
+		logrus.Debugf("CORS header is enabled and set to: %s", corsHeaders)
+		w.Header().Add("Access-Control-Allow-Origin", corsHeaders)
+		w.Header().Add("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, X-Registry-Auth")
+		w.Header().Add("Access-Control-Allow-Methods", "HEAD, GET, POST, DELETE, PUT, OPTIONS")
+		return handler(ctx, w, r, vars)
+	}
 }

api/server/middleware/debug.go

@@ -13,7 +13,7 @@ import (
 )
 
 // DebugRequestMiddleware dumps the request to logger
-func DebugRequestMiddleware(handler httputils.APIFunc) httputils.APIFunc {
+func DebugRequestMiddleware(handler func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
 	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
 		logrus.Debugf("Calling %s %s", r.Method, r.RequestURI)
 

api/server/middleware/middleware.go

@@ -1,7 +1,13 @@
 package middleware
 
-import "github.com/docker/docker/api/server/httputils"
+import (
+	"net/http"
 
-// Middleware is an adapter to allow the use of ordinary functions as Docker API filters.
-// Any function that has the appropriate signature can be registered as a middleware.
-type Middleware func(handler httputils.APIFunc) httputils.APIFunc
+	"golang.org/x/net/context"
+)
+
+// Middleware is an interface to allow the use of ordinary functions as Docker API filters.
+// Any struct that has the appropriate signature can be registered as a middleware.
+type Middleware interface {
+	WrapHandler(func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error
+}

api/server/middleware/user_agent.go

@@ -10,28 +10,38 @@ import (
 	"golang.org/x/net/context"
 )
 
-// NewUserAgentMiddleware creates a new UserAgent middleware.
-func NewUserAgentMiddleware(versionCheck string) Middleware {
-	serverVersion := version.Version(versionCheck)
-
-	return func(handler httputils.APIFunc) httputils.APIFunc {
-		return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
-			ctx = context.WithValue(ctx, httputils.UAStringKey, r.Header.Get("User-Agent"))
-
-			if strings.Contains(r.Header.Get("User-Agent"), "Docker-Client/") {
-				userAgent := strings.Split(r.Header.Get("User-Agent"), "/")
-
-				// v1.20 onwards includes the GOOS of the client after the version
-				// such as Docker/1.7.0 (linux)
-				if len(userAgent) == 2 && strings.Contains(userAgent[1], " ") {
-					userAgent[1] = strings.Split(userAgent[1], " ")[0]
-				}
-
-				if len(userAgent) == 2 && !serverVersion.Equal(version.Version(userAgent[1])) {
-					logrus.Debugf("Client and server don't have the same version (client: %s, server: %s)", userAgent[1], serverVersion)
-				}
+// UserAgentMiddleware is a middleware that
+// validates the client user-agent.
+type UserAgentMiddleware struct {
+	serverVersion version.Version
+}
+
+// NewUserAgentMiddleware creates a new UserAgentMiddleware
+// with the server version.
+func NewUserAgentMiddleware(s version.Version) UserAgentMiddleware {
+	return UserAgentMiddleware{
+		serverVersion: s,
+	}
+}
+
+// WrapHandler returns a new handler function wrapping the previous one in the request chain.
+func (u UserAgentMiddleware) WrapHandler(handler func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+		ctx = context.WithValue(ctx, httputils.UAStringKey, r.Header.Get("User-Agent"))
+
+		if strings.Contains(r.Header.Get("User-Agent"), "Docker-Client/") {
+			userAgent := strings.Split(r.Header.Get("User-Agent"), "/")
+
+			// v1.20 onwards includes the GOOS of the client after the version
+			// such as Docker/1.7.0 (linux)
+			if len(userAgent) == 2 && strings.Contains(userAgent[1], " ") {
+				userAgent[1] = strings.Split(userAgent[1], " ")[0]
+			}
+
+			if len(userAgent) == 2 && !u.serverVersion.Equal(version.Version(userAgent[1])) {
+				logrus.Debugf("Client and server don't have the same version (client: %s, server: %s)", userAgent[1], u.serverVersion)
 			}
-			return handler(ctx, w, r, vars)
 		}
+		return handler(ctx, w, r, vars)
 	}
 }

api/server/middleware/version.go

@@ -5,7 +5,6 @@ import (
 	"net/http"
 	"runtime"
 
-	"github.com/docker/docker/api/server/httputils"
 	"github.com/docker/docker/pkg/version"
 	"golang.org/x/net/context"
 )
@@ -18,28 +17,43 @@ func (badRequestError) HTTPErrorStatusCode() int {
 	return http.StatusBadRequest
 }
 
-// NewVersionMiddleware creates a new Version middleware.
-func NewVersionMiddleware(versionCheck string, defaultVersion, minVersion version.Version) Middleware {
-	serverVersion := version.Version(versionCheck)
-
-	return func(handler httputils.APIFunc) httputils.APIFunc {
-		return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
-			apiVersion := version.Version(vars["version"])
-			if apiVersion == "" {
-				apiVersion = defaultVersion
-			}
-
-			if apiVersion.GreaterThan(defaultVersion) {
-				return badRequestError{fmt.Errorf("client is newer than server (client API version: %s, server API version: %s)", apiVersion, defaultVersion)}
-			}
-			if apiVersion.LessThan(minVersion) {
-				return badRequestError{fmt.Errorf("client version %s is too old. Minimum supported API version is %s, please upgrade your client to a newer version", apiVersion, minVersion)}
-			}
-
-			header := fmt.Sprintf("Docker/%s (%s)", serverVersion, runtime.GOOS)
-			w.Header().Set("Server", header)
-			ctx = context.WithValue(ctx, httputils.APIVersionKey, apiVersion)
-			return handler(ctx, w, r, vars)
+// VersionMiddleware is a middleware that
+// validates the client and server versions.
+type VersionMiddleware struct {
+	serverVersion  version.Version
+	defaultVersion version.Version
+	minVersion     version.Version
+}
+
+// NewVersionMiddleware creates a new VersionMiddleware
+// with the default versions.
+func NewVersionMiddleware(s, d, m version.Version) VersionMiddleware {
+	return VersionMiddleware{
+		serverVersion:  s,
+		defaultVersion: d,
+		minVersion:     m,
+	}
+}
+
+// WrapHandler returns a new handler function wrapping the previous one in the request chain.
+func (v VersionMiddleware) WrapHandler(handler func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+		apiVersion := version.Version(vars["version"])
+		if apiVersion == "" {
+			apiVersion = v.defaultVersion
 		}
+
+		if apiVersion.GreaterThan(v.defaultVersion) {
+			return badRequestError{fmt.Errorf("client is newer than server (client API version: %s, server API version: %s)", apiVersion, v.defaultVersion)}
+		}
+		if apiVersion.LessThan(v.minVersion) {
+			return badRequestError{fmt.Errorf("client version %s is too old. Minimum supported API version is %s, please upgrade your client to a newer version", apiVersion, v.minVersion)}
+		}
+
+		header := fmt.Sprintf("Docker/%s (%s)", v.serverVersion, runtime.GOOS)
+		w.Header().Set("Server", header)
+		ctx = context.WithValue(ctx, "api-version", apiVersion)
+		return handler(ctx, w, r, vars)
 	}
+
 }

api/server/middleware/version_test.go

@@ -21,8 +21,8 @@ func TestVersionMiddleware(t *testing.T) {
 
 	defaultVersion := version.Version("1.10.0")
 	minVersion := version.Version("1.2.0")
-	m := NewVersionMiddleware(defaultVersion.String(), defaultVersion, minVersion)
-	h := m(handler)
+	m := NewVersionMiddleware(defaultVersion, defaultVersion, minVersion)
+	h := m.WrapHandler(handler)
 
 	req, _ := http.NewRequest("GET", "/containers/json", nil)
 	resp := httptest.NewRecorder()
@@ -42,8 +42,8 @@ func TestVersionMiddlewareWithErrors(t *testing.T) {
 
 	defaultVersion := version.Version("1.10.0")
 	minVersion := version.Version("1.2.0")
-	m := NewVersionMiddleware(defaultVersion.String(), defaultVersion, minVersion)
-	h := m(handler)
+	m := NewVersionMiddleware(defaultVersion, defaultVersion, minVersion)
+	h := m.WrapHandler(handler)
 
 	req, _ := http.NewRequest("GET", "/containers/json", nil)
 	resp := httptest.NewRecorder()

api/server/server.go

@@ -8,8 +8,8 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/api/server/httputils"
+	"github.com/docker/docker/api/server/middleware"
 	"github.com/docker/docker/api/server/router"
-	"github.com/docker/docker/pkg/authorization"
 	"github.com/gorilla/mux"
 	"golang.org/x/net/context"
 )
@@ -20,22 +20,21 @@ const versionMatcher = "/v{version:[0-9.]+}"
 
 // Config provides the configuration for the API server
 type Config struct {
-	Logging                  bool
-	EnableCors               bool
-	CorsHeaders              string
-	AuthorizationPluginNames []string
-	Version                  string
-	SocketGroup              string
-	TLSConfig                *tls.Config
+	Logging     bool
+	EnableCors  bool
+	CorsHeaders string
+	Version     string
+	SocketGroup string
+	TLSConfig   *tls.Config
 }
 
 // Server contains instance details for the server
 type Server struct {
 	cfg           *Config
 	servers       []*HTTPServer
 	routers       []router.Router
-	authZPlugins  []authorization.Plugin
 	routerSwapper *routerSwapper
+	middlewares   []middleware.Middleware
 }
 
 // New returns a new instance of the server based on the specified configuration.
@@ -46,6 +45,12 @@ func New(cfg *Config) *Server {
 	}
 }
 
+// UseMiddleware appends a new middleware to the request chain.
+// This needs to be called before the API routes are configured.
+func (s *Server) UseMiddleware(m middleware.Middleware) {
+	s.middlewares = append(s.middlewares, m)
+}
+
 // Accept sets a listener the server accepts connections into.
 func (s *Server) Accept(addr string, listeners ...net.Listener) {
 	for _, listener := range listeners {