server: Apply review comments and split basic handler

server/etcdserver/api/etcdhttp/utils.go

@@ -0,0 +1,92 @@
+// Copyright 2022 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package etcdhttp
+
+import (
+	"net/http"
+
+	"go.etcd.io/etcd/server/v3/etcdserver"
+	httptypes "go.etcd.io/etcd/server/v3/etcdserver/api/etcdhttp/types"
+	"go.etcd.io/etcd/server/v3/etcdserver/api/v2error"
+	"go.uber.org/zap"
+)
+
+func allowMethod(w http.ResponseWriter, r *http.Request, m string) bool {
+	if m == r.Method {
+		return true
+	}
+	w.Header().Set("Allow", m)
+	http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
+	return false
+}
+
+// writeError logs and writes the given Error to the ResponseWriter
+// If Error is an etcdErr, it is rendered to the ResponseWriter
+// Otherwise, it is assumed to be a StatusInternalServerError
+func writeError(lg *zap.Logger, w http.ResponseWriter, r *http.Request, err error) {
+	if err == nil {
+		return
+	}
+	switch e := err.(type) {
+	case *v2error.Error:
+		e.WriteTo(w)
+
+	case *httptypes.HTTPError:
+		if et := e.WriteTo(w); et != nil {
+			if lg != nil {
+				lg.Debug(
+					"failed to write v2 HTTP error",
+					zap.String("remote-addr", r.RemoteAddr),
+					zap.String("internal-server-error", e.Error()),
+					zap.Error(et),
+				)
+			}
+		}
+
+	default:
+		switch err {
+		case etcdserver.ErrTimeoutDueToLeaderFail, etcdserver.ErrTimeoutDueToConnectionLost, etcdserver.ErrNotEnoughStartedMembers,
+			etcdserver.ErrUnhealthy:
+			if lg != nil {
+				lg.Warn(
+					"v2 response error",
+					zap.String("remote-addr", r.RemoteAddr),
+					zap.String("internal-server-error", err.Error()),
+				)
+			}
+
+		default:
+			if lg != nil {
+				lg.Warn(
+					"unexpected v2 response error",
+					zap.String("remote-addr", r.RemoteAddr),
+					zap.String("internal-server-error", err.Error()),
+				)
+			}
+		}
+
+		herr := httptypes.NewHTTPError(http.StatusInternalServerError, "Internal Server Error")
+		if et := herr.WriteTo(w); et != nil {
+			if lg != nil {
+				lg.Debug(
+					"failed to write v2 HTTP error",
+					zap.String("remote-addr", r.RemoteAddr),
+					zap.String("internal-server-error", err.Error()),
+					zap.Error(et),
+				)
+			}
+		}
+	}
+}