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minio/cmd/net-rpc-client.go

165 lines
4.7 KiB

/*
* 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 (
"bufio"
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"io"
"net"
"net/http"
"net/rpc"
"sync"
"time"
)
// defaultDialTimeout is used for non-secure connection.
const defaultDialTimeout = 3 * time.Second
// RPCClient is a reconnectable RPC client on Call().
type RPCClient struct {
sync.Mutex // Mutex to lock net rpc client.
netRPCClient *rpc.Client // Base RPC client to make any RPC call.
serverAddr string // RPC server address.
serviceEndpoint string // Endpoint on the server to make any RPC call.
secureConn bool // Make TLS connection to RPC server or not.
}
// newRPCClient returns new RPCClient object with given serverAddr and serviceEndpoint.
// It does lazy connect to the remote endpoint on Call().
func newRPCClient(serverAddr, serviceEndpoint string, secureConn bool) *RPCClient {
return &RPCClient{
serverAddr: serverAddr,
serviceEndpoint: serviceEndpoint,
secureConn: secureConn,
}
}
// dial tries to establish a connection to serverAddr in a safe manner.
// If there is a valid rpc.Cliemt, it returns that else creates a new one.
func (rpcClient *RPCClient) dial() (netRPCClient *rpc.Client, err error) {
rpcClient.Lock()
defer rpcClient.Unlock()
// Nothing to do as we already have valid connection.
if rpcClient.netRPCClient != nil {
return rpcClient.netRPCClient, nil
}
var conn net.Conn
if rpcClient.secureConn {
var hostname string
if hostname, _, err = net.SplitHostPort(rpcClient.serverAddr); err != nil {
err = &net.OpError{
Op: "dial-http",
Net: rpcClient.serverAddr + rpcClient.serviceEndpoint,
Addr: nil,
Err: fmt.Errorf("Unable to parse server address <%s>: %s", rpcClient.serverAddr, err.Error()),
}
return nil, err
}
// ServerName in tls.Config needs to be specified to support SNI certificates.
conn, err = tls.Dial("tcp", rpcClient.serverAddr, &tls.Config{ServerName: hostname, RootCAs: globalRootCAs})
} else {
// Dial with a timeout.
conn, err = net.DialTimeout("tcp", rpcClient.serverAddr, defaultDialTimeout)
}
if err != nil {
// Print RPC connection errors that are worthy to display in log.
switch err.(type) {
case x509.HostnameError:
errorIf(err, "Unable to establish secure connection to %s", rpcClient.serverAddr)
}
return nil, &net.OpError{
Op: "dial-http",
Net: rpcClient.serverAddr + rpcClient.serviceEndpoint,
Addr: nil,
Err: err,
}
}
io.WriteString(conn, "CONNECT "+rpcClient.serviceEndpoint+" HTTP/1.0\n\n")
// Require successful HTTP response before switching to RPC protocol.
resp, err := http.ReadResponse(bufio.NewReader(conn), &http.Request{Method: "CONNECT"})
if err == nil && resp.Status == "200 Connected to Go RPC" {
netRPCClient := rpc.NewClient(conn)
if netRPCClient == nil {
return nil, &net.OpError{
Op: "dial-http",
Net: rpcClient.serverAddr + rpcClient.serviceEndpoint,
Addr: nil,
Err: fmt.Errorf("Unable to initialize new rpc.Client, %s", errUnexpected),
}
}
rpcClient.netRPCClient = netRPCClient
return netRPCClient, nil
}
conn.Close()
if err == nil {
err = errors.New("unexpected HTTP response: " + resp.Status)
}
return nil, &net.OpError{
Op: "dial-http",
Net: rpcClient.serverAddr + rpcClient.serviceEndpoint,
Addr: nil,
Err: err,
}
}
// Call makes a RPC call to the remote endpoint using the default codec, namely encoding/gob.
func (rpcClient *RPCClient) Call(serviceMethod string, args interface{}, reply interface{}) error {
// Get a new or existing rpc.Client.
netRPCClient, err := rpcClient.dial()
if err != nil {
return err
}
return netRPCClient.Call(serviceMethod, args, reply)
}
// Close closes underlying rpc.Client.
func (rpcClient *RPCClient) Close() error {
rpcClient.Lock()
if rpcClient.netRPCClient != nil {
// We make a copy of rpc.Client and unlock it immediately so that another
// goroutine could try to dial or close in parallel.
netRPCClient := rpcClient.netRPCClient
rpcClient.netRPCClient = nil
rpcClient.Unlock()
return netRPCClient.Close()
}
rpcClient.Unlock()
return nil
}