Implement HTTP POST based RPC (#5840)

Added support for new RPC support using HTTP POST.  RPC's 
arguments and reply are Gob encoded and sent as HTTP 
request/response body.

This patch also removes Go RPC based implementation.

cmd/peer-rpc-server.go

@@ -0,0 +1,207 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * 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 cmd
+
+import (
+	"context"
+	"fmt"
+	"path"
+
+	"github.com/gorilla/mux"
+	"github.com/minio/minio/cmd/logger"
+	xrpc "github.com/minio/minio/cmd/rpc"
+	"github.com/minio/minio/pkg/auth"
+	"github.com/minio/minio/pkg/event"
+	xnet "github.com/minio/minio/pkg/net"
+	"github.com/minio/minio/pkg/policy"
+)
+
+const peerServiceName = "Peer"
+const peerServiceSubPath = "/s3/remote"
+
+var peerServicePath = path.Join(minioReservedBucketPath, peerServiceSubPath)
+
+// peerRPCReceiver - Peer RPC receiver for peer RPC server.
+type peerRPCReceiver struct{}
+
+// DeleteBucketArgs - delete bucket RPC arguments.
+type DeleteBucketArgs struct {
+	AuthArgs
+	BucketName string
+}
+
+// DeleteBucket - handles delete bucket RPC call which removes all values of given bucket in global NotificationSys object.
+func (receiver *peerRPCReceiver) DeleteBucket(args *DeleteBucketArgs, reply *VoidReply) error {
+	globalNotificationSys.RemoveNotification(args.BucketName)
+	globalPolicySys.Remove(args.BucketName)
+	return nil
+}
+
+// SetBucketPolicyArgs - set bucket policy RPC arguments.
+type SetBucketPolicyArgs struct {
+	AuthArgs
+	BucketName string
+	Policy     policy.Policy
+}
+
+// SetBucketPolicy - handles set bucket policy RPC call which adds bucket policy to globalPolicySys.
+func (receiver *peerRPCReceiver) SetBucketPolicy(args *SetBucketPolicyArgs, reply *VoidReply) error {
+	globalPolicySys.Set(args.BucketName, args.Policy)
+	return nil
+}
+
+// RemoveBucketPolicyArgs - delete bucket policy RPC arguments.
+type RemoveBucketPolicyArgs struct {
+	AuthArgs
+	BucketName string
+}
+
+// RemoveBucketPolicy - handles delete bucket policy RPC call which removes bucket policy to globalPolicySys.
+func (receiver *peerRPCReceiver) RemoveBucketPolicy(args *RemoveBucketPolicyArgs, reply *VoidReply) error {
+	globalPolicySys.Remove(args.BucketName)
+	return nil
+}
+
+// PutBucketNotificationArgs - put bucket notification RPC arguments.
+type PutBucketNotificationArgs struct {
+	AuthArgs
+	BucketName string
+	RulesMap   event.RulesMap
+}
+
+// PutBucketNotification - handles put bucket notification RPC call which adds rules to given bucket to global NotificationSys object.
+func (receiver *peerRPCReceiver) PutBucketNotification(args *PutBucketNotificationArgs, reply *VoidReply) error {
+	globalNotificationSys.AddRulesMap(args.BucketName, args.RulesMap)
+	return nil
+}
+
+// ListenBucketNotificationArgs - listen bucket notification RPC arguments.
+type ListenBucketNotificationArgs struct {
+	AuthArgs   `json:"-"`
+	BucketName string         `json:"-"`
+	EventNames []event.Name   `json:"eventNames"`
+	Pattern    string         `json:"pattern"`
+	TargetID   event.TargetID `json:"targetId"`
+	Addr       xnet.Host      `json:"addr"`
+}
+
+// ListenBucketNotification - handles listen bucket notification RPC call. It creates PeerRPCClient target which pushes requested events to target in remote peer.
+func (receiver *peerRPCReceiver) ListenBucketNotification(args *ListenBucketNotificationArgs, reply *VoidReply) error {
+	rpcClient := globalNotificationSys.GetPeerRPCClient(args.Addr)
+	if rpcClient == nil {
+		return fmt.Errorf("unable to find PeerRPCClient for provided address %v. This happens only if remote and this minio run with different set of endpoints", args.Addr)
+	}
+
+	target := NewPeerRPCClientTarget(args.BucketName, args.TargetID, rpcClient)
+	rulesMap := event.NewRulesMap(args.EventNames, args.Pattern, target.ID())
+	if err := globalNotificationSys.AddRemoteTarget(args.BucketName, target, rulesMap); err != nil {
+		reqInfo := &logger.ReqInfo{BucketName: target.bucketName}
+		reqInfo.AppendTags("target", target.id.Name)
+		ctx := logger.SetReqInfo(context.Background(), reqInfo)
+		logger.LogIf(ctx, err)
+		return err
+	}
+	return nil
+}
+
+// RemoteTargetExistArgs - remote target ID exist RPC arguments.
+type RemoteTargetExistArgs struct {
+	AuthArgs
+	BucketName string
+	TargetID   event.TargetID
+}
+
+// RemoteTargetExist - handles target ID exist RPC call which checks whether given target ID is a HTTP client target or not.
+func (receiver *peerRPCReceiver) RemoteTargetExist(args *RemoteTargetExistArgs, reply *bool) error {
+	*reply = globalNotificationSys.RemoteTargetExist(args.BucketName, args.TargetID)
+	return nil
+}
+
+// SendEventArgs - send event RPC arguments.
+type SendEventArgs struct {
+	AuthArgs
+	Event      event.Event
+	TargetID   event.TargetID
+	BucketName string
+}
+
+// SendEvent - handles send event RPC call which sends given event to target by given target ID.
+func (receiver *peerRPCReceiver) SendEvent(args *SendEventArgs, reply *bool) error {
+	// Set default to true to keep the target.
+	*reply = true
+	errs := globalNotificationSys.send(args.BucketName, args.Event, args.TargetID)
+
+	for i := range errs {
+		reqInfo := (&logger.ReqInfo{}).AppendTags("Event", args.Event.EventName.String())
+		reqInfo.AppendTags("targetName", args.TargetID.Name)
+		ctx := logger.SetReqInfo(context.Background(), reqInfo)
+		logger.LogIf(ctx, errs[i].Err)
+
+		*reply = false // send failed i.e. do not keep the target.
+		return errs[i].Err
+	}
+
+	return nil
+}
+
+// SetCredentialsArgs - set credentials RPC arguments.
+type SetCredentialsArgs struct {
+	AuthArgs
+	Credentials auth.Credentials
+}
+
+// SetCredentials - handles set credentials RPC call.
+func (receiver *peerRPCReceiver) SetCredentials(args *SetCredentialsArgs, reply *VoidReply) error {
+	if !args.Credentials.IsValid() {
+		return fmt.Errorf("invalid credentials passed")
+	}
+
+	// Acquire lock before updating global configuration.
+	globalServerConfigMu.Lock()
+	defer globalServerConfigMu.Unlock()
+
+	// Update credentials in memory
+	prevCred := globalServerConfig.SetCredential(args.Credentials)
+
+	// Save credentials to config file
+	if err := globalServerConfig.Save(); err != nil {
+		// As saving configurstion failed, restore previous credential in memory.
+		globalServerConfig.SetCredential(prevCred)
+
+		logger.LogIf(context.Background(), err)
+		return err
+	}
+
+	return nil
+}
+
+// NewPeerRPCServer - returns new peer RPC server.
+func NewPeerRPCServer() (*xrpc.Server, error) {
+	rpcServer := xrpc.NewServer()
+	if err := rpcServer.RegisterName(peerServiceName, &peerRPCReceiver{}); err != nil {
+		return nil, err
+	}
+	return rpcServer, nil
+}
+
+// registerPeerRPCRouter - creates and registers Peer RPC server and its router.
+func registerPeerRPCRouter(router *mux.Router) {
+	rpcServer, err := NewPeerRPCServer()
+	logger.CriticalIf(context.Background(), err)
+	subrouter := router.PathPrefix(minioReservedBucketPath).Subrouter()
+	subrouter.Path(peerServiceSubPath).Handler(rpcServer)
+}