leader election: Display replica status in docker info.

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

api/handlers.go

@@ -27,7 +27,7 @@ func getInfo(c *context, w http.ResponseWriter, r *http.Request) {
 	info := dockerclient.Info{
 		Containers:      int64(len(c.cluster.Containers())),
 		Images:          int64(len(c.cluster.Images())),
-		DriverStatus:    c.cluster.Info(),
+		DriverStatus:    c.statusHandler.Status(),
 		NEventsListener: int64(c.eventsHandler.Size()),
 		Debug:           c.debug,
 		MemoryLimit:     true,

api/proxy.go

@@ -2,18 +2,24 @@ package api
 
 import (
 	"crypto/tls"
+	"fmt"
 	"net/http"
+	"strings"
 )
 
+var localRoutes = []string{"/info", "/_ping"}
+
 // ReverseProxy is a Docker reverse proxy.
 type ReverseProxy struct {
+	api       http.Handler
 	tlsConfig *tls.Config
 	dest      string
 }
 
 // NewReverseProxy creates a new reverse proxy.
-func NewReverseProxy(tlsConfig *tls.Config) *ReverseProxy {
+func NewReverseProxy(api http.Handler, tlsConfig *tls.Config) *ReverseProxy {
 	return &ReverseProxy{
+		api:       api,
 		tlsConfig: tlsConfig,
 	}
 }
@@ -26,12 +32,21 @@ func (p *ReverseProxy) SetDestination(dest string) {
 
 // ServeHTTP is the http.Handler.
 func (p *ReverseProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// Check whether we should handle this request locally.
+	for _, route := range localRoutes {
+		if strings.HasSuffix(r.URL.Path, route) {
+			p.api.ServeHTTP(w, r)
+			return
+		}
+	}
+
+	// Otherwise, forward.
 	if p.dest == "" {
 		httpError(w, "No cluster leader", http.StatusInternalServerError)
 		return
 	}
 
 	if err := hijack(p.tlsConfig, p.dest, w, r); err != nil {
-		httpError(w, err.Error(), http.StatusInternalServerError)
+		httpError(w, fmt.Sprintf("Unable to reach cluster leader: %v", err), http.StatusInternalServerError)
 	}
 }

api/router.go

@@ -13,6 +13,7 @@ import (
 type context struct {
 	cluster       cluster.Cluster
 	eventsHandler *eventsHandler
+	statusHandler StatusHandler
 	debug         bool
 	tlsConfig     *tls.Config
 }
@@ -83,7 +84,7 @@ func writeCorsHeaders(w http.ResponseWriter, r *http.Request) {
 }
 
 // NewRouter creates a new API router.
-func NewRouter(cluster cluster.Cluster, tlsConfig *tls.Config, enableCors bool) *mux.Router {
+func NewRouter(cluster cluster.Cluster, tlsConfig *tls.Config, status StatusHandler, enableCors bool) *mux.Router {
 	// Register the API events handler in the cluster.
 	eventsHandler := newEventsHandler()
 	cluster.RegisterEventHandler(eventsHandler)
@@ -91,6 +92,7 @@ func NewRouter(cluster cluster.Cluster, tlsConfig *tls.Config, enableCors bool)
 	context := &context{
 		cluster:       cluster,
 		eventsHandler: eventsHandler,
+		statusHandler: status,
 		tlsConfig:     tlsConfig,
 	}
 

api/status.go

@@ -0,0 +1,7 @@
+package api
+
+// StatusHandler allows the API to display extra information on docker info.
+type StatusHandler interface {
+	// Info provides key/values to be added to docker info.
+	Status() [][]string
+}