Layered rpc-client implementation (#2512)

cmd/auth-rpc-client.go

@@ -0,0 +1,79 @@
+/*
+ * Minio Cloud Storage, (C) 2016 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 (
+	"time"
+
+	"github.com/minio/dsync"
+)
+
+// AuthRPCClient is a wrapper type for RPCClient which provides JWT based authentication across reconnects.
+type AuthRPCClient struct {
+	rpc         *RPCClient // reconnect'able rpc client built on top of net/rpc Client
+	cred        credential // AccessKey and SecretKey
+	token       string     // JWT based token
+	tstamp      time.Time  // Timestamp as received on Login RPC.
+	loginMethod string     // RPC service name for authenticating using JWT
+}
+
+// newAuthClient - returns a jwt based authenticated (go) rpc client, which does automatic reconnect.
+func newAuthClient(node, rpcPath string, cred credential, loginMethod string) *AuthRPCClient {
+	return &AuthRPCClient{
+		rpc:         newClient(node, rpcPath),
+		cred:        cred,
+		loginMethod: loginMethod,
+	}
+}
+
+// Close - closes underlying rpc connection.
+func (authClient *AuthRPCClient) Close() error {
+	// reset token on closing a connection
+	authClient.token = ""
+	return authClient.rpc.Close()
+}
+
+// Login - a jwt based authentication is performed with rpc server.
+func (authClient *AuthRPCClient) Login() (string, time.Time, error) {
+	reply := RPCLoginReply{}
+	if err := authClient.rpc.Call(authClient.loginMethod, RPCLoginArgs{
+		Username: authClient.cred.AccessKeyID,
+		Password: authClient.cred.SecretAccessKey,
+	}, &reply); err != nil {
+		return "", time.Time{}, err
+	}
+	return reply.Token, reply.Timestamp, nil
+}
+
+// Call - If rpc connection isn't established yet since previous disconnect,
+// connection is established, a jwt authenticated login is performed and then
+// the call is performed.
+func (authClient *AuthRPCClient) Call(serviceMethod string, args dsync.TokenSetter, reply interface{}) (err error) {
+	if authClient.token == "" {
+		token, tstamp, err := authClient.Login()
+		if err != nil {
+			return err
+		}
+		// set token, time stamp as received from a successful login call.
+		authClient.token = token
+		authClient.tstamp = tstamp
+		// Update the RPC call's token with that received from the recent login call.
+		args.SetToken(token)
+		args.SetTimestamp(tstamp)
+	}
+	return authClient.rpc.Call(serviceMethod, args, reply)
+}