Add basic apiserver backend

Signed-off-by: Ben Firshman <ben@firshman.co.uk>

backends/apiserver.go

@@ -0,0 +1,118 @@
+package backends
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/docker/libswarm/beam"
+	"github.com/dotcloud/docker/api"
+	"github.com/dotcloud/docker/pkg/version"
+	"github.com/gorilla/mux"
+	"net"
+	"net/http"
+)
+
+func ApiServer() beam.Sender {
+	backend := beam.NewServer()
+	backend.OnSpawn(beam.Handler(func(ctx *beam.Message) error {
+		instance := beam.Task(func(in beam.Receiver, out beam.Sender) {
+			err := listenAndServe("tcp", "0.0.0.0:4243", out)
+			if err != nil {
+				fmt.Printf("listenAndServe: %v", err)
+			}
+		})
+		_, err := ctx.Ret.Send(&beam.Message{Verb: beam.Ack, Ret: instance})
+		return err
+	}))
+	return backend
+}
+
+type HttpApiFunc func(out beam.Sender, version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error
+
+func listenAndServe(proto, addr string, out beam.Sender) error {
+	fmt.Println("Starting API server...")
+	r, err := createRouter(out)
+	if err != nil {
+		return err
+	}
+	l, err := net.Listen(proto, addr)
+	if err != nil {
+		return err
+	}
+	httpSrv := http.Server{Addr: addr, Handler: r}
+	return httpSrv.Serve(l)
+}
+
+func ping(out beam.Sender, version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	_, err := w.Write([]byte{'O', 'K'})
+	return err
+}
+
+func getContainersJSON(out beam.Sender, version version.Version, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
+	if err := r.ParseForm(); err != nil {
+		return err
+	}
+
+	o := beam.Obj(out)
+	names, err := o.Ls()
+	if err != nil {
+		return err
+	}
+
+	return writeJSON(w, 200, names)
+}
+
+func createRouter(out beam.Sender) (*mux.Router, error) {
+	r := mux.NewRouter()
+	m := map[string]map[string]HttpApiFunc{
+		"GET": {
+			"/_ping":           ping,
+			"/containers/json": getContainersJSON,
+		},
+		"POST":    {},
+		"DELETE":  {},
+		"OPTIONS": {},
+	}
+
+	for method, routes := range m {
+		for route, fct := range routes {
+			localRoute := route
+			localFct := fct
+			localMethod := method
+
+			f := makeHttpHandler(out, localMethod, localRoute, localFct, version.Version("0.11.0"))
+
+			// add the new route
+			if localRoute == "" {
+				r.Methods(localMethod).HandlerFunc(f)
+			} else {
+				r.Path("/v{version:[0-9.]+}" + localRoute).Methods(localMethod).HandlerFunc(f)
+				r.Path(localRoute).Methods(localMethod).HandlerFunc(f)
+			}
+		}
+	}
+
+	return r, nil
+}
+
+func makeHttpHandler(out beam.Sender, localMethod string, localRoute string, handlerFunc HttpApiFunc, dockerVersion version.Version) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		// log the request
+		fmt.Printf("Calling %s %s\n", localMethod, localRoute)
+
+		version := version.Version(mux.Vars(r)["version"])
+		if version == "" {
+			version = api.APIVERSION
+		}
+
+		if err := handlerFunc(out, version, w, r, mux.Vars(r)); err != nil {
+			fmt.Printf("Error: %s", err)
+		}
+	}
+}
+
+func writeJSON(w http.ResponseWriter, code int, v interface{}) error {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(code)
+	enc := json.NewEncoder(w)
+	return enc.Encode(v)
+}

backends/backends.go

@@ -17,5 +17,6 @@ func New() *beam.Object {
 	backends.Bind("fakeclient", FakeClient())
 	backends.Bind("forward", Forward())
 	backends.Bind("exec", Exec())
+	backends.Bind("apiserver", ApiServer())
 	return beam.Obj(backends)
 }