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server.go
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server.go
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// Package cprpc was forked from the standard package net/rpc:
// https://golang.org/pkg/net/rpc/
// Original work Copyright 2009 The Go Authors
// Modified work Copyright 2019 Hmgle (dustgle@gmail.com)
// All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package cprpc
import (
"bufio"
"context"
"encoding/gob"
"errors"
"io"
"log"
"net"
"net/http"
"reflect"
"sync"
"sync/atomic"
"time"
)
const (
// DefaultRPCPath used by HandleHTTP
DefaultRPCPath = "/_goRPC_"
// DefaultDebugPath used by HandleHTTP
DefaultDebugPath = "/debug/rpc"
)
// Request is a header written before every RPC call. It is used internally
// but documented here as an aid to debugging, such as when analyzing
// network traffic.
type Request struct {
Path string
Seq uint64 // sequence number chosen by client
next *Request // for free list in Server
}
// Response is a header written before every RPC return. It is used internally
// but documented here as an aid to debugging, such as when analyzing
// network traffic.
type Response struct {
Path string
Seq uint64 // echoes that of the request
Error string // error, if any.
next *Response // for free list in Server
}
type rpcConn struct {
numActiveReq int32
rwc io.ReadWriteCloser
}
func newRPCConn(c io.ReadWriteCloser) *rpcConn {
return &rpcConn{
rwc: c,
}
}
func (rc *rpcConn) incrNumReq() {
atomic.AddInt32(&rc.numActiveReq, 1)
}
func (rc *rpcConn) decrNumReq() {
atomic.AddInt32(&rc.numActiveReq, -1)
}
func (rc *rpcConn) numReq() int32 {
return atomic.LoadInt32(&rc.numActiveReq)
}
// ErrServerClosed is returned by the Server's Serve method
// after a call to Shutdown or Close.
var ErrServerClosed = errors.New("cprpc: Server closed")
// Server represents an RPC Server.
type Server struct {
reqLock sync.Mutex // protects freeReq
freeReq *Request
respLock sync.Mutex // protects freeResp
freeResp *Response
apis map[string]API
mu sync.Mutex
listeners map[net.Listener]struct{}
activeConn map[*rpcConn]struct{}
inShutdown int32 // accessed atomically (non-zero means we're in Shutdown)
}
// NewServer returns a new Server.
func NewServer() *Server {
return &Server{
apis: make(map[string]API),
}
}
// DefaultServer is the default instance of *Server.
var DefaultServer = NewServer()
// Context including Server, seq, ServerCodec and sync.Mutex.
type Context struct {
conn *Server
seq uint64
req *Request
codec ServerCodec
sending *sync.Mutex
}
// A API implements the Serve method.
type API interface {
Serve(*Context)
}
// RegisterAPI bind the path to api.
func (server *Server) RegisterAPI(path string, api API) {
server.apis[path] = api
}
// A value sent as a placeholder for the server's response value when the server
// receives an invalid request. It is never decoded by the client since the Response
// contains an error when it is used.
var invalidRequest = struct{}{}
func (server *Server) sendResponse(sending *sync.Mutex, req *Request, reply interface{}, codec ServerCodec, errmsg string) {
resp := server.getResponse()
// Encode the response header
resp.Path = req.Path
if errmsg != "" {
resp.Error = errmsg
reply = invalidRequest
}
resp.Seq = req.Seq
sending.Lock()
err := codec.WriteResponse(resp, reply)
if err != nil {
log.Println("rpc: writing response:", err)
}
sending.Unlock()
server.freeResponse(resp)
}
// ReplyOk reply ok data.
func (ctx *Context) ReplyOk(ret interface{}) {
ctx.conn.sendResponse(ctx.sending, ctx.req, ret, ctx.codec, "")
ctx.conn.freeRequest(ctx.req)
}
type gobServerCodec struct {
rwc io.ReadWriteCloser
dec *gob.Decoder
enc *gob.Encoder
encBuf *bufio.Writer
closed bool
}
func (c *gobServerCodec) ReadRequestHeader(r *Request) error {
return c.dec.Decode(r)
}
func (c *gobServerCodec) ReadRequestBody(body interface{}) error {
return c.dec.Decode(body)
}
func (c *gobServerCodec) WriteResponse(r *Response, body interface{}) (err error) {
if err = c.enc.Encode(r); err != nil {
if c.encBuf.Flush() == nil {
// Gob couldn't encode the header. Should not happen, so if it does,
// shut down the connection to signal that the connection is broken.
log.Println("rpc: gob error encoding response:", err)
c.Close()
}
return
}
if err = c.enc.Encode(body); err != nil {
if c.encBuf.Flush() == nil {
// Was a gob problem encoding the body but the header has been written.
// Shut down the connection to signal that the connection is broken.
log.Println("rpc: gob error encoding body:", err)
c.Close()
}
return
}
return c.encBuf.Flush()
}
func (c *gobServerCodec) Close() error {
if c.closed {
// Only call c.rwc.Close once; otherwise the semantics are undefined.
return nil
}
c.closed = true
return c.rwc.Close()
}
func (c *gobServerCodec) GetRwc() io.ReadWriteCloser {
return c.rwc
}
// ServeConn runs the server on a single connection.
// ServeConn blocks, serving the connection until the client hangs up.
// The caller typically invokes ServeConn in a go statement.
// ServeConn uses the gob wire format (see package gob) on the
// connection. To use an alternate codec, use ServeCodec.
// See NewClient's comment for information about concurrent access.
func (server *Server) ServeConn(conn io.ReadWriteCloser) {
buf := bufio.NewWriter(conn)
srv := &gobServerCodec{
rwc: conn,
dec: gob.NewDecoder(conn),
enc: gob.NewEncoder(buf),
encBuf: buf,
}
server.ServeCodec(srv)
}
// ServeCodec is like ServeConn but uses the specified codec to
// decode requests and encode responses.
func (server *Server) ServeCodec(codec ServerCodec) {
rc := newRPCConn(codec.GetRwc())
server.trackConn(rc, true)
sending := new(sync.Mutex)
wg := new(sync.WaitGroup)
for {
api, req, keepReading, err := server.readRequest(codec, rc)
if err != nil {
if !keepReading {
break
}
// send a response if we actually managed to read a header.
if req != nil {
server.sendResponse(sending, req, invalidRequest, codec, err.Error())
server.freeRequest(req)
}
rc.decrNumReq()
continue
}
wg.Add(1)
go func() {
defer func() {
if r := recover(); r != nil {
log.Printf("bad recover: %v", r)
}
}()
api.Serve(&Context{
conn: server,
seq: req.Seq,
req: req,
codec: codec,
sending: sending,
})
rc.decrNumReq()
wg.Done()
}()
}
// We've seen that there are no more requests.
// Wait for responses to be sent before closing codec.
wg.Wait()
codec.Close()
server.trackConn(rc, false)
}
// ServeRequest is like ServeCodec but synchronously serves a single request.
// It does not close the codec upon completion.
func (server *Server) ServeRequest(codec ServerCodec) error {
rc := newRPCConn(codec.GetRwc())
server.trackConn(rc, true)
sending := new(sync.Mutex)
api, req, keepReading, err := server.readRequest(codec, rc)
if err != nil {
defer rc.decrNumReq()
if !keepReading {
return err
}
// send a response if we actually managed to read a header.
if req != nil {
server.sendResponse(sending, req, invalidRequest, codec, err.Error())
server.freeRequest(req)
}
return err
}
api.Serve(&Context{
conn: server,
seq: req.Seq,
req: req,
codec: codec,
sending: sending,
})
rc.decrNumReq()
return nil
}
func (server *Server) getRequest() *Request {
server.reqLock.Lock()
req := server.freeReq
if req == nil {
req = new(Request)
} else {
server.freeReq = req.next
*req = Request{}
}
server.reqLock.Unlock()
return req
}
func (server *Server) freeRequest(req *Request) {
server.reqLock.Lock()
req.next = server.freeReq
server.freeReq = req
server.reqLock.Unlock()
}
func (server *Server) getResponse() *Response {
server.respLock.Lock()
resp := server.freeResp
if resp == nil {
resp = new(Response)
} else {
server.freeResp = resp.next
*resp = Response{}
}
server.respLock.Unlock()
return resp
}
func (server *Server) freeResponse(resp *Response) {
server.respLock.Lock()
resp.next = server.freeResp
server.freeResp = resp
server.respLock.Unlock()
}
func (server *Server) readRequest(codec ServerCodec, rc *rpcConn) (api API, req *Request, keepReading bool, err error) {
api, req, keepReading, err = server.readRequestHeader(codec)
rc.incrNumReq()
if err != nil {
if !keepReading {
return
}
// discard body
codec.ReadRequestBody(nil)
return
}
if err = codec.ReadRequestBody(api); err != nil {
log.Panic(err)
}
return
}
func (server *Server) readRequestHeader(codec ServerCodec) (api API, req *Request, keepReading bool, err error) {
// Grab the request header.
req = server.getRequest()
err = codec.ReadRequestHeader(req)
if err != nil {
req = nil
if err == io.EOF || err == io.ErrUnexpectedEOF {
return
}
err = errors.New("rpc: server cannot decode request: " + err.Error())
return
}
// We read the header successfully. If we see an error now,
// we can still recover and move on to the next request.
keepReading = true
if originAPI, ok := server.apis[req.Path]; ok {
if reflect.TypeOf(originAPI).Kind() == reflect.Ptr {
api = reflect.New(reflect.ValueOf(originAPI).Elem().Type()).Interface().(API)
} else {
api = reflect.New(reflect.TypeOf(originAPI)).Elem().Interface().(API)
}
} else {
err = errors.New("rpc: can't find path " + req.Path)
}
return
}
func (server *Server) serve(lis net.Listener) error {
defer lis.Close()
if !server.trackListener(lis, true) {
return ErrServerClosed
}
defer server.trackListener(lis, false)
for {
conn, err := lis.Accept()
if err != nil {
if server.shuttingDown() {
atomic.StoreInt32(&server.inShutdown, 0)
return ErrServerClosed
}
return err
}
go func() {
defer func() {
if r := recover(); r != nil {
log.Printf("bad recover: %v", r)
}
}()
server.ServeConn(conn)
}()
}
}
// shutdownPollInterval is how often we poll for quiescence
// during Server.Shutdown. This is lower during tests, to
// speed up tests.
var shutdownPollInterval = 500 * time.Millisecond
// Shutdown gracefully shuts down the server without interrupting any
// active connections. Shutdown works by first closing all open
// listeners, then closing all idle connections, and then waiting
// indefinitely for connections to return to idle and then shut down.
// If the provided context expires before the shutdown is complete,
// Shutdown returns the context's error, otherwise it returns any
// error returned from closing the Server's underlying Listener(s).
func (server *Server) Shutdown(ctx context.Context) error {
atomic.StoreInt32(&server.inShutdown, 1)
server.mu.Lock()
lnerr := server.closeListenersLocked()
server.mu.Unlock()
ticker := time.NewTicker(shutdownPollInterval)
defer ticker.Stop()
for {
if server.closeIdleConns() {
return lnerr
}
select {
case <-ctx.Done():
return ctx.Err()
case <-ticker.C:
}
}
}
// Close immediately closes all active net.Listeners and any
// connections in state StateNew, StateActive, or StateIdle. For a
// graceful shutdown, use Shutdown.
func (server *Server) Close() error {
atomic.StoreInt32(&server.inShutdown, 1)
server.mu.Lock()
defer server.mu.Unlock()
err := server.closeListenersLocked()
for rc := range server.activeConn {
rc.rwc.Close()
delete(server.activeConn, rc)
}
return err
}
func (server *Server) closeListenersLocked() error {
var err error
for ln := range server.listeners {
if cerr := ln.Close(); err != nil {
err = cerr
}
delete(server.listeners, ln)
}
return err
}
func (server *Server) trackConnUnlock(rc *rpcConn, add bool) {
if server.activeConn == nil {
server.activeConn = make(map[*rpcConn]struct{})
}
if add {
server.activeConn[rc] = struct{}{}
} else {
delete(server.activeConn, rc)
}
}
func (server *Server) trackConn(rc *rpcConn, add bool) {
server.mu.Lock()
defer server.mu.Unlock()
if server.activeConn == nil {
server.activeConn = make(map[*rpcConn]struct{})
}
if add {
server.activeConn[rc] = struct{}{}
} else {
delete(server.activeConn, rc)
}
}
func (server *Server) shuttingDown() bool {
return atomic.LoadInt32(&server.inShutdown) != 0
}
func (server *Server) trackListener(lis net.Listener, add bool) bool {
server.mu.Lock()
defer server.mu.Unlock()
if server.listeners == nil {
server.listeners = make(map[net.Listener]struct{})
}
if add {
if server.shuttingDown() {
return false
}
server.listeners[lis] = struct{}{}
} else {
delete(server.listeners, lis)
}
return true
}
// closeIdleConns closes all idle connections and reports whether the
// server is quiescent.
func (server *Server) closeIdleConns() bool {
server.mu.Lock()
defer server.mu.Unlock()
quiescent := true
for rc := range server.activeConn {
if rc.numReq() == 0 {
rc.rwc.Close()
server.trackConnUnlock(rc, false)
} else {
quiescent = false
}
}
return quiescent
}
// A ServerCodec implements reading of RPC requests and writing of
// RPC responses for the server side of an RPC session.
// The server calls ReadRequestHeader and ReadRequestBody in pairs
// to read requests from the connection, and it calls WriteResponse to
// write a response back. The server calls Close when finished with the
// connection. ReadRequestBody may be called with a nil
// argument to force the body of the request to be read and discarded.
// See NewClient's comment for information about concurrent access.
type ServerCodec interface {
ReadRequestHeader(*Request) error
ReadRequestBody(interface{}) error
WriteResponse(*Response, interface{}) error
// Close can be called multiple times and must be idempotent.
Close() error
GetRwc() io.ReadWriteCloser
}
// ServeConn runs the DefaultServer on a single connection.
// ServeConn blocks, serving the connection until the client hangs up.
// The caller typically invokes ServeConn in a go statement.
// ServeConn uses the gob wire format (see package gob) on the
// connection. To use an alternate codec, use ServeCodec.
// See NewClient's comment for information about concurrent access.
func ServeConn(conn io.ReadWriteCloser) {
DefaultServer.ServeConn(conn)
}
// ServeCodec is like ServeConn but uses the specified codec to
// decode requests and encode responses.
func ServeCodec(codec ServerCodec) {
DefaultServer.ServeCodec(codec)
}
// ServeRequest is like ServeCodec but synchronously serves a single request.
// It does not close the codec upon completion.
func ServeRequest(codec ServerCodec) error {
return DefaultServer.ServeRequest(codec)
}
// Serve accepts connections on the listener and serves requests
// to DefaultServer for each incoming connection.
// Accept blocks; the caller typically invokes it in a go statement.
func Serve(lis net.Listener) error {
return DefaultServer.Serve(lis)
}
// Can connect to RPC service using HTTP CONNECT to rpcPath.
var connected = "200 Connected to Go RPC"
// ServeHTTP implements an http.Handler that answers RPC requests.
func (server *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
if req.Method != "CONNECT" {
w.Header().Set("Content-Type", "text/plain; charset=utf-8")
w.WriteHeader(http.StatusMethodNotAllowed)
io.WriteString(w, "405 must CONNECT\n")
return
}
conn, _, err := w.(http.Hijacker).Hijack()
if err != nil {
log.Print("rpc hijacking ", req.RemoteAddr, ": ", err.Error())
return
}
io.WriteString(conn, "HTTP/1.0 "+connected+"\n\n")
server.ServeConn(conn)
}
// HandleHTTP registers an HTTP handler for RPC messages on rpcPath,
// and a debugging handler on debugPath.
// It is still necessary to invoke http.Serve(), typically in a go statement.
func (server *Server) HandleHTTP(rpcPath, debugPath string) {
http.Handle(rpcPath, server)
}
// HandleHTTP registers an HTTP handler for RPC messages to DefaultServer
// on DefaultRPCPath and a debugging handler on DefaultDebugPath.
// It is still necessary to invoke http.Serve(), typically in a go statement.
func HandleHTTP() {
DefaultServer.HandleHTTP(DefaultRPCPath, DefaultDebugPath)
}
// Shutdown gracefully shuts down the DefaultServer without interrupting any
// active connection. Shutdown works by first closing all DefaultServer's
// open listeners, then waiting indefinitely for connections to transition to
// an idle state before closing them and shutting down. If the provided context
// expires before the shutdown is complete, Shutdown forcibly closes active
// connections and returns the context's error, otherwise it returns any error
// returned from closing the DefaultServer's underlying Listener(s).
func Shutdown(ctx context.Context) error {
return DefaultServer.Shutdown(ctx)
}