136 lines
4.1 KiB
Go
136 lines
4.1 KiB
Go
/*
|
|
* 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 (
|
|
"errors"
|
|
"net/rpc"
|
|
"sync"
|
|
)
|
|
|
|
// RPCClient is a wrapper type for rpc.Client which provides reconnect on first failure.
|
|
type RPCClient struct {
|
|
mu sync.Mutex
|
|
rpcPrivate *rpc.Client
|
|
node string
|
|
rpcPath string
|
|
}
|
|
|
|
// newClient constructs a RPCClient object with node and rpcPath initialized.
|
|
// It _doesn't_ connect to the remote endpoint. See Call method to see when the
|
|
// connect happens.
|
|
func newClient(node, rpcPath string) *RPCClient {
|
|
return &RPCClient{
|
|
node: node,
|
|
rpcPath: rpcPath,
|
|
}
|
|
}
|
|
|
|
// clearRPCClient clears the pointer to the rpc.Client object in a safe manner
|
|
func (rpcClient *RPCClient) clearRPCClient() {
|
|
rpcClient.mu.Lock()
|
|
rpcClient.rpcPrivate = nil
|
|
rpcClient.mu.Unlock()
|
|
}
|
|
|
|
// getRPCClient gets the pointer to the rpc.Client object in a safe manner
|
|
func (rpcClient *RPCClient) getRPCClient() *rpc.Client {
|
|
rpcClient.mu.Lock()
|
|
rpcLocalStack := rpcClient.rpcPrivate
|
|
rpcClient.mu.Unlock()
|
|
return rpcLocalStack
|
|
}
|
|
|
|
// dialRPCClient tries to establish a connection to the server in a safe manner
|
|
func (rpcClient *RPCClient) dialRPCClient() (*rpc.Client, error) {
|
|
rpcClient.mu.Lock()
|
|
defer rpcClient.mu.Unlock()
|
|
// After acquiring lock, check whether another thread may not have already dialed and established connection
|
|
if rpcClient.rpcPrivate != nil {
|
|
return rpcClient.rpcPrivate, nil
|
|
}
|
|
rpc, err := rpc.DialHTTPPath("tcp", rpcClient.node, rpcClient.rpcPath)
|
|
if err != nil {
|
|
return nil, err
|
|
} else if rpc == nil {
|
|
return nil, errors.New("No valid RPC Client created after dial")
|
|
}
|
|
rpcClient.rpcPrivate = rpc
|
|
return rpcClient.rpcPrivate, nil
|
|
}
|
|
|
|
// 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 {
|
|
// Make a copy below so that we can safely (continue to) work with the rpc.Client.
|
|
// Even in the case the two threads would simultaneously find that the connection is not initialised,
|
|
// they would both attempt to dial and only one of them would succeed in doing so.
|
|
rpcLocalStack := rpcClient.getRPCClient()
|
|
|
|
// If the rpc.Client is nil, we attempt to (re)connect with the remote endpoint.
|
|
if rpcLocalStack == nil {
|
|
var err error
|
|
rpcLocalStack, err = rpcClient.dialRPCClient()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
// If the RPC fails due to a network-related error, then we reset
|
|
// rpc.Client for a subsequent reconnect.
|
|
err := rpcLocalStack.Call(serviceMethod, args, reply)
|
|
if err != nil {
|
|
if err.Error() == rpc.ErrShutdown.Error() {
|
|
// Reset rpcClient.rpc to nil to trigger a reconnect in future
|
|
// and close the underlying connection.
|
|
rpcClient.clearRPCClient()
|
|
|
|
// Close the underlying connection.
|
|
rpcLocalStack.Close()
|
|
|
|
// Set rpc error as rpc.ErrShutdown type.
|
|
err = rpc.ErrShutdown
|
|
}
|
|
}
|
|
return err
|
|
}
|
|
|
|
// Close closes the underlying socket file descriptor.
|
|
func (rpcClient *RPCClient) Close() error {
|
|
// See comment above for making a copy on local stack
|
|
rpcLocalStack := rpcClient.getRPCClient()
|
|
|
|
// If rpc client has not connected yet there is nothing to close.
|
|
if rpcLocalStack == nil {
|
|
return nil
|
|
}
|
|
|
|
// Reset rpcClient.rpc to allow for subsequent calls to use a new
|
|
// (socket) connection.
|
|
rpcClient.clearRPCClient()
|
|
return rpcLocalStack.Close()
|
|
}
|
|
|
|
// Node returns the node (network address) of the connection
|
|
func (rpcClient *RPCClient) Node() string {
|
|
return rpcClient.node
|
|
}
|
|
|
|
// RPCPath returns the RPC path of the connection
|
|
func (rpcClient *RPCClient) RPCPath() string {
|
|
return rpcClient.rpcPath
|
|
}
|