server/prpc: updated server according to protocol

server/prpc/server.go

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package prpc
 
 import (
+        "fmt"
         "net/http"
         "sort"
         "sync"
 
         "github.com/julienschmidt/httprouter"
         "golang.org/x/net/context"
         "google.golang.org/grpc"
+        "google.golang.org/grpc/codes"
 
+        "github.com/luci/luci-go/common/logging"
         "github.com/luci/luci-go/server/auth"
         "github.com/luci/luci-go/server/middleware"
 )
 
 // Server is a pRPC server to serve RPC requests.
 // Zero value is valid.
 type Server struct {
         // CustomAuthenticator, if true, disables the forced authentication set by
         // RegisterDefaultAuth.
         CustomAuthenticator bool
@@ skipping 41 matching lines @@
         if a == nil {
                 panicf("prpc: CustomAuthenticator is false, but default authenticator was not registered. " +
                         "Forgot to import appengine/gaeauth/server package?")
         }
 
         return func(h middleware.Handler) httprouter.Handle {
                 return base(func(c context.Context, w http.ResponseWriter, r *http.Request, p httprouter.Params) {
                         c = auth.SetAuthenticator(c, a)
                         c, err := a.Authenticate(c, r)
                         if err != nil {
-                                writeError(c, w, withStatus(err, http.StatusUnauthorized))
+                                res := errResponse(codes.Unauthenticated, http.StatusUnauthorized, err.Error())
+                                res.write(c, w)
                                 return
                         }
                         h(c, w, r, p)
                 })
         }
 }
 
-// InstallHandlers installs HTTP POST handlers at
-// /prpc/{service_name}/{method_name} for all registered services.
+// InstallHandlers installs HTTP handlers at /prpc/:service/:method.
+// See https://godoc.org/github.com/luci/luci-go/common/prpc#hdr-Protocol
+// for pRPC protocol.
 func (s *Server) InstallHandlers(r *httprouter.Router, base middleware.Base) {
         s.mu.Lock()
         defer s.mu.Unlock()
 
         if !s.CustomAuthenticator {
                 base = s.authenticate(base)
         }
 
-        for _, service := range s.services {
-                for _, m := range service.methods {
-                        m.InstallHandlers(r, base)
-                }
+        const path = "/prpc/:service/:method"
+        handle := base(s.handle)
+        r.POST(path, handle)

[dnj (Google), 2016/01/26 16:13:57]

Do we need to support all of these methods? I thought we were only doing POST.
If not, leave the others for httprouter to 404.

Is StatusMethodNotAllowed important here? If so, we're not setting the Allow
headers accordingly. I don't think there's any value in returning
MethodNotAllowed over 404, though, so let's just not register endpoints we don't
have.

[nodir, 2016/01/26 18:01:07]

We had this discussion and decided to handle all methods and include grpc code
in the response.
Included Allow in response.

[dnj, 2016/01/26 18:50:27]

Seems pointless, but OK. IMO either a client knows what it's doing (POST,
protocol, etc.) or it doesn't, and in the latter case this won't help it at all.
I see no value at all to being partially RESTful. We're abusing HTTP/POST here
to implement RPC. I don't think there's any value in trying to have conformance
in this single minor area, moreso b/c basically nothing at all will consume this
response code meaningfully.

If you're going to do this, implement a simple separate handle method that
returns StatusMethodNotAllowed.

r.POST(path, handle)
r.GET(path, handleNotAllowed)
etc.

[nodir, 2016/01/26 19:06:09]

ah, Server.handle was exported at some point, that's why it checked method. 
Anyway, removed other methods and updated protocol.

+        r.GET(path, handle)
+        r.PUT(path, handle)
+        r.DELETE(path, handle)
+        r.PATCH(path, handle)
+}
+
+// handle handles RPCs.
+// See https://godoc.org/github.com/luci/luci-go/common/prpc#hdr-Protocol
+// for pRPC protocol.
+func (s *Server) handle(c context.Context, w http.ResponseWriter, r *http.Request, p httprouter.Params) {
+        res := s.respond(c, w, r, p)

[dnj (Google), 2016/01/26 16:13:57]

nit: pull service/method out of params up front, then pass them to respond().

[nodir, 2016/01/26 18:01:07]

Done.

+
+        c = logging.SetFields(c, logging.Fields{
+                "Service": p.ByName("service"),
+                "Method":  p.ByName("method"),
+        })
+        res.write(c, w)
+}
+
+func (s *Server) respond(c context.Context, w http.ResponseWriter, r *http.Request, p httprouter.Params) *response {
+        if r.Method != "POST" {
+                return errResponse(codes.Unimplemented, http.StatusMethodNotAllowed, "HTTP method must be POST")
         }
+
+        serviceName := p.ByName("service")
+        service := s.services[serviceName]
+        if service == nil {
+                return errResponse(
+                        codes.Unimplemented,
+                        http.StatusNotImplemented,
+                        fmt.Sprintf("service %q is not implemented", serviceName))
+        }
+
+        methodName := p.ByName("method")
+        method := service.methods[methodName]
+        if method == nil {
+                return errResponse(
+                        codes.Unimplemented,
+                        http.StatusNotImplemented,
+                        fmt.Sprintf("method %q in service %q is not implemented", methodName, serviceName))
+        }
+
+        return method.handle(c, w, r)
 }
 
 // ServiceNames returns a sorted list of full names of all registered services.
 func (s *Server) ServiceNames() []string {
         s.mu.Lock()
         defer s.mu.Unlock()
 
         names := make([]string, 0, len(s.services))
         for name := range s.services {
                 names = append(names, name)
         }
         sort.Strings(names)
         return names
 }