[Golang] 剑走偏锋 -- IoComplete ports
前言
Golang 目前的主要應用領域還是後臺微服務，雖然在業務領域也有所應用但仍然是比較小衆的選擇。大多數的服務運行環境都是linux，而在windows中golang應用更少，而作者因爲特殊情況，不得已要在widows環境中用golang去寫本地代理服務。在我的使用場景中實時性要求非常高（視頻通信），對tcp數據處理要足夠快，否則會造成TCP 服務端的 Receive Buffer 溢出造成 Packet loss，影響實時性和數據的完整性。
作者閲讀了golang 在windows 環境下 tcp 部分syscall 的實現，最終確認它的底層模型是用了完成端口（異步IO模型）的。
但是由於作者本人比較喜歡折騰，所以用golang 底層的syscall 實現了一下tcp 完成端口服務。
IoCompletion Port
以下為windows環境下用golang實現的 IoCompletion Port Server
IoCompletionRootContext
管理指定 Port 上所有 accepted socket:
type IoCompletionRootContext struct {
socket windows.Handle
socketAddr windows.SockaddrInet4
ioSet []*IoCompletionContext
sync.Mutex
}
func (root *IoCompletionRootContext) NewIoContext() *IoCompletionContext {
root.Lock()
defer root.Unlock()
res := &IoCompletionContext{
data: make([]byte, 65535),
overlapped: windows.Overlapped{
Internal: 0,
InternalHigh: 0,
Offset: 0,
OffsetHigh: 0,
HEvent: 0,
},
}
res.wsaBuf.Buf = &res.data[0]
res.wsaBuf.Len = uint32(65535)
root.ioSet = append(root.ioSet, res)
return res
}
func NewRootContext() *IoCompletionRootContext {
return &IoCompletionRootContext{
ioSet: make([]*IoCompletionContext, 0),
}
}IoCompletionContext
accepted socket 的上下文：
type IoCompletionContext struct {
socket windows.Handle
socketAddr windows.SockaddrInet4
wsaBuf windows.WSABuf
data []byte
opType OP_TYPE
overlapped windows.Overlapped
}IoCompletionServer
完成端口服務:
type IoCompletionServer struct {
Addr string
Port int
recvFunc func(data []byte) error
rootCtx *IoCompletionRootContext
// 爲了防止内存移動，采用此種方式
accepts sync.Map
hIOCompletionPort windows.Handle
}
func (ss *IoCompletionServer) saveIoRootCtx(id uint32, ctx *IoCompletionRootContext) {
ss.accepts.Store(id, ctx)
}
func (ss *IoCompletionServer) loadIoRootCtx(id uint32) *IoCompletionRootContext {
if id == uint32(ss.rootCtx.socket) {
return ss.rootCtx
}
if v, isOk := ss.accepts.Load(id); isOk {
if res, isOk := v.(*IoCompletionRootContext); isOk {
return res
}
}
return nil
}
func (ss *IoCompletionServer) remove(id uint32) {
ss.accepts.Delete(id)
}
func (ss *IoCompletionServer) RegisterReceiveFunc(rfunc func([]byte) error) {
ss.recvFunc = rfunc
}
func (ss *IoCompletionServer) Listen() {
dwBytesTransfered := uint32(0)
var ctxId uint32
var overlapped *windows.Overlapped
for {
err := windows.GetQueuedCompletionStatus(ss.hIOCompletionPort, &dwBytesTransfered,
&ctxId, &overlapped, windows.INFINITE)
if err != nil {
fmt.Printf("syscall.GetQueuedCompletionStatus: %v\n", err)
}
if overlapped == nil {
continue
}
// 通过位移取得ioCtx
ioCtx := (*IoCompletionContext)(unsafe.Pointer(uintptr(unsafe.Pointer(overlapped)) - unsafe.Offsetof(IoCompletionContext{}.overlapped)))
switch ioCtx.opType {
case ACCEPT_POSTED:
{
ss.DoAcceptEx(ss.loadIoRootCtx(ctxId), ioCtx)
}
case RECV_POSTED:
{
ss.DoReceive(ss.loadIoRootCtx(ctxId), ioCtx)
}
case SEND_POSTED:
case NULL_POSTED:
default:
}
}
}
func (ss *IoCompletionServer) DoAcceptEx(rootCtx *IoCompletionRootContext, ioCtx *IoCompletionContext) (err error) {
nFdCtx := NewRootContext()
nFdCtx.socket = ioCtx.socket
addrSize := uint32(unsafe.Sizeof(windows.RawSockaddrAny{}))
var localAddr, remoteAddr *windows.RawSockaddrAny
lrsalen := int32(addrSize)
rrsalen := int32(addrSize)
// 與windows C++ 不同，此處函數無需去函數指針即可使用
windows.GetAcceptExSockaddrs(ioCtx.wsaBuf.Buf, ioCtx.wsaBuf.Len-(addrSize+16)*2,
addrSize+16, addrSize+16, &localAddr, &lrsalen, &remoteAddr, &rrsalen)
if ss.recvFunc != nil {
ss.recvFunc(ioCtx.data[:ioCtx.overlapped.InternalHigh])
}
// 继承listen socket的属性
err = windows.Setsockopt(nFdCtx.socket, windows.SOL_SOCKET, windows.SO_UPDATE_ACCEPT_CONTEXT,
(*byte)(unsafe.Pointer(&ss.rootCtx.socket)), int32(unsafe.Sizeof(ss.rootCtx.socket)))
if err != nil {
return errors.Wrap(err, "syscall.AcceptEx")
}
err = windows.SetsockoptInt(nFdCtx.socket, windows.SOL_SOCKET, windows.SO_RCVBUF, 65535)
if err != nil {
return errors.Wrap(err, "windows.SetsockoptInt")
}
// 綁定到完成端口, 此步驟很關鍵
handle, err := windows.CreateIoCompletionPort(nFdCtx.socket,
ss.hIOCompletionPort, uint32(nFdCtx.socket), 0)
if err != nil {
return errors.Wrap(err, "syscall.CreateIoCompletionPort")
} else {
fmt.Println(handle, rootCtx.socket)
}
// 投遞接收請求, 此處可以自行修改
for i := 0; i < 16; i++ {
nFdIoCtx := nFdCtx.NewIoContext()
nFdIoCtx.socket = nFdCtx.socket
if err = ss.Receive(nFdIoCtx); err != nil {
return err
}
}
//投遞接收連接請求
if err = ss.AcceptEx(ioCtx); err != nil {
return err
}
// 保存到context中
ss.saveIoRootCtx(uint32(nFdCtx.socket), nFdCtx)
return nil
}
func (ss *IoCompletionServer) AcceptEx(ctx *IoCompletionContext) (err error) {
ctx.socket = windows.Handle(C.mWSASocket())
dwBytes := uint32(0)
addrSize := uint32(unsafe.Sizeof(windows.RawSockaddrAny{}))
ctx.opType = ACCEPT_POSTED
//err = syscall.AcceptEx(ss.rootCtx.socket, ctx.socket, ctx.wsaBuf.Buf,
// ctx.wsaBuf.Len-2*(addrSize+16), addrSize+16,
// addrSize+16, &dwBytes, &ctx.overlapped)
//windows.WSAIoctl(ss.rootCtx.socket, windows.SIO_GET_EXTENSION_FUNCTION_POINTER)
err = windows.AcceptEx(ss.rootCtx.socket, ctx.socket, ctx.wsaBuf.Buf,
ctx.wsaBuf.Len-2*(addrSize+16), addrSize+16,
addrSize+16, &dwBytes, &ctx.overlapped)
if err != nil {
if err == windows.Errno(997) { // ERROR_IO_PENDING 表示尚未接收到鏈接
err = nil
} else {
err = errors.Wrap(err, "syscall.AcceptEx")
}
}
return err
}
func (ss *IoCompletionServer) DoReceive(rootCtx *IoCompletionRootContext, ctx *IoCompletionContext) {
if ctx.overlapped.InternalHigh == 0 {
if rootCtx != nil {
ss.remove(uint32(rootCtx.socket))
C.mClose(C.int(rootCtx.socket))
}
return
}
if ss.recvFunc != nil {
ss.recvFunc(ctx.data[:ctx.overlapped.InternalHigh])
}
ss.Receive(ctx)
}
func (ss *IoCompletionServer) Receive(ioCtx *IoCompletionContext) error {
recv := uint32(0)
flags := uint32(0)
ioCtx.opType = RECV_POSTED
err := windows.WSARecv(ioCtx.socket, &ioCtx.wsaBuf,
1, &recv, &flags, &ioCtx.overlapped, nil)
if err != nil {
if err == windows.Errno(997) { // ERROR_IO_PENDING 表示尚未接收到數據
err = nil
} else {
err = errors.Wrap(err, "syscall.AcceptEx")
}
}
return err
}
func setDefaultSockOpt(handle windows.Handle) error {
err := windows.SetsockoptInt(handle, windows.SOL_SOCKET, windows.SO_REUSEADDR, 1)
if err != nil {
return errors.Wrap(err, "syscall.SetsockoptInt")
}
//err = windows.SetsockoptInt(handle, windows.SOL_SOCKET, windows.SO, 1)
//if err != nil {
// return errors.Wrap(err, "syscall.SetsockoptInt")
//}
return nil
}
func (ss *IoCompletionServer) Start() error {
fmt.Println(windows.WSAStartup(2, &windows.WSAData{}))
// 初始創建一個用於綁定的 listen socket 的 IoCompletion 句柄
hIOCompletionPort, err := windows.CreateIoCompletionPort(windows.InvalidHandle, 0, 0, 0)
if err != nil {
return errors.Wrap(err, "syscall.CreateIoCompletionPort")
}
ss.hIOCompletionPort = hIOCompletionPort
rootCtx := NewRootContext()
rootCtx.socket = windows.Handle(C.mWSASocket())
setDefaultSockOpt(rootCtx.socket)
ss.rootCtx = rootCtx
handle, err := windows.CreateIoCompletionPort(rootCtx.socket,
hIOCompletionPort, uint32(ss.rootCtx.socket), 0)
if err != nil {
return errors.Wrap(err, "syscall.CreateIoCompletionPort")
} else {
fmt.Println(handle, rootCtx.socket)
}
sockAddr := windows.SockaddrInet4{}
sockAddr.Port = ss.Port
if err := windows.Bind(rootCtx.socket, &sockAddr); err != nil {
return errors.Wrap(err, "syscall.Bind")
}
if err := windows.Listen(rootCtx.socket, MAX_POST_ACCEPT); err != nil {
return errors.Wrap(err, "windows.Listen")
}
ss.rootCtx = rootCtx
if err := ss.AcceptEx(rootCtx.NewIoContext()); err != nil {
return err
}
return nil
}example
完成端口服務使用示例:
ss = &StreamServer{
Addr: "127.0.0.1:10050",
Port: 10050,
accepts: sync.Map{},
}
ss.RegisterReceiveFunc(func(data []byte) error {
fmt.Println("receive data len:", string(data))
return nil
})
// 可以啓動多個携程來接收請求，但是需要特別注意的是
// 多携程可能會導致接受數據包時序發生亂序
ss.Listen()結尾
以上代碼經過實際測試檢驗，可以正常使用，尚未與標準庫進行 效率\性能 對比，沒有實現 send 功能,此處需要提醒的是,使用 IoCompletion Port 發送數據要注意時序的把握。
IoCompletion Port 是windows 系統中十分優秀的IO模型, 深入瞭解其工作機制及原理, 也有助於我們對操作系統 IO 數據處理的機制有更清晰的認知。
參考
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