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msgserver.go
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msgserver.go
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// Package server is used to wrap the p2p services to define multiple req-res messages under one protocol.
package server
import (
"container/list"
"github.com/spacemeshos/go-spacemesh/log"
"github.com/spacemeshos/go-spacemesh/p2p/p2pcrypto"
"github.com/spacemeshos/go-spacemesh/p2p/service"
"runtime"
"sync"
"sync/atomic"
"time"
)
// MessageType is a uint32 used to distinguish between server messages inside a single protocol.
type MessageType uint32
// Message is helper type for `MessegeServer` messages.
type Message interface {
service.DirectMessage
Data() service.Data
}
func extractPayload(m Message) []byte {
data := m.Data().(*service.DataMsgWrapper)
return data.Payload
}
// Item is queue entry used to match responds to sent requests.
type Item struct {
id uint64
timestamp time.Time
}
// MessageServer is a request-response multiplexer on top of the p2p layer. it provides a way to register
// message types on top of a protocol and declare request and response handlers. it matches incoming responses to requests.
type MessageServer struct {
log.Log
ReqID uint64 //request id
name string //server name
network Service
pendMutex sync.RWMutex
pendingQueue *list.List //queue of pending messages
resHandlers map[uint64]func(msg []byte) //response handlers by request ReqID
msgRequestHandlers map[MessageType]func(message Message) []byte //request handlers by request type
ingressChannel chan service.DirectMessage //chan to relay messages into the server
requestLifetime time.Duration //time a request can stay in the pending queue until evicted
workerCount sync.WaitGroup
workerLimiter chan struct{}
exit chan struct{}
}
// Service is the subset of method used by MessageServer for p2p communications.
type Service interface {
RegisterDirectProtocolWithChannel(protocol string, ingressChannel chan service.DirectMessage) chan service.DirectMessage
SendWrappedMessage(nodeID p2pcrypto.PublicKey, protocol string, payload *service.DataMsgWrapper) error
}
// NewMsgServer registers a protocol and returns a new server to declare request and response handlers on.
func NewMsgServer(network Service, name string, requestLifetime time.Duration, c chan service.DirectMessage, logger log.Log) *MessageServer {
p := &MessageServer{
Log: logger,
name: name,
resHandlers: make(map[uint64]func(msg []byte)),
pendingQueue: list.New(),
network: network,
ingressChannel: network.RegisterDirectProtocolWithChannel(name, c),
msgRequestHandlers: make(map[MessageType]func(message Message) []byte),
requestLifetime: requestLifetime,
exit: make(chan struct{}),
workerLimiter: make(chan struct{}, runtime.NumCPU()),
}
go p.readLoop()
return p
}
// Close stops the MessageServer
func (p *MessageServer) Close() {
p.exit <- struct{}{}
<-p.exit
p.workerCount.Wait()
}
// readLoop reads incoming messages and matches them to requests or responses.
func (p *MessageServer) readLoop() {
timer := time.NewTicker(p.requestLifetime + time.Millisecond*100)
defer timer.Stop()
for {
select {
case <-p.exit:
p.With().Debug("shutting down protocol", log.String("protocol", p.name))
close(p.exit)
return
case <-timer.C:
go p.cleanStaleMessages()
case msg, ok := <-p.ingressChannel:
p.Debug("new msg received from channel")
if !ok {
p.Error("read loop channel was closed")
return
}
p.workerCount.Add(1)
p.workerLimiter <- struct{}{}
go func(msg Message) {
p.handleMessage(msg)
<-p.workerLimiter
p.workerCount.Done()
}(msg.(Message))
}
}
}
// clean stale messages after requests life time expire.
func (p *MessageServer) cleanStaleMessages() {
for {
p.pendMutex.RLock()
elem := p.pendingQueue.Front()
p.pendMutex.RUnlock()
if elem != nil {
item := elem.Value.(Item)
if time.Since(item.timestamp) > p.requestLifetime {
p.With().Debug("cleanStaleMessages remove request", log.Uint64("id", item.id))
p.removeFromPending(item.id)
} else {
p.Debug("cleanStaleMessages no more stale messages")
return
}
} else {
p.Debug("cleanStaleMessages queue empty")
return
}
}
}
func (p *MessageServer) removeFromPending(reqID uint64) {
var next *list.Element
p.pendMutex.Lock()
for e := p.pendingQueue.Front(); e != nil; e = next {
next = e.Next()
if reqID == e.Value.(Item).id {
p.pendingQueue.Remove(e)
p.With().Debug("removed request", log.Uint64("request_id", reqID))
break
}
}
p.With().Debug("delete request result handler", log.Uint64("request_id", reqID))
delete(p.resHandlers, reqID)
p.pendMutex.Unlock()
}
func (p *MessageServer) handleMessage(msg Message) {
data := msg.Data().(*service.DataMsgWrapper)
if data.Req {
p.handleRequestMessage(msg, data)
} else {
p.handleResponseMessage(data)
}
}
func (p *MessageServer) handleRequestMessage(msg Message, data *service.DataMsgWrapper) {
p.Debug("handleRequestMessage start")
foo, okFoo := p.msgRequestHandlers[MessageType(data.MsgType)]
if !okFoo {
p.With().Error("handler missing for request",
log.Uint64("request_id", data.ReqID),
log.String("protocol", p.name),
log.Uint32("msg_type", data.MsgType))
return
}
p.Debug("handle request type %v", data.MsgType)
rmsg := &service.DataMsgWrapper{MsgType: data.MsgType, ReqID: data.ReqID, Payload: foo(msg)}
if sendErr := p.network.SendWrappedMessage(msg.Sender(), p.name, rmsg); sendErr != nil {
p.With().Error("Error sending response message", log.Err(sendErr))
}
p.Debug("handleRequestMessage close")
}
func (p *MessageServer) handleResponseMessage(headers *service.DataMsgWrapper) {
//get and remove from pendingMap
p.Log.With().Debug("handleResponseMessage", log.Uint64("request_id", headers.ReqID))
p.pendMutex.RLock()
foo, okFoo := p.resHandlers[headers.ReqID]
p.pendMutex.RUnlock()
p.removeFromPending(headers.ReqID)
if okFoo {
foo(headers.Payload)
} else {
p.With().Error("can't find handler", log.Uint64("request_id", headers.ReqID))
}
p.Debug("handleResponseMessage close")
}
// RegisterMsgHandler sets the handler to act on a specific message request.
func (p *MessageServer) RegisterMsgHandler(msgType MessageType, reqHandler func(message Message) []byte) {
p.msgRequestHandlers[msgType] = reqHandler
}
func handlerFromBytesHandler(in func(msg []byte) []byte) func(message Message) []byte {
return func(message Message) []byte {
payload := extractPayload(message)
return in(payload)
}
}
// RegisterBytesMsgHandler sets the handler to act on a specific message request.
func (p *MessageServer) RegisterBytesMsgHandler(msgType MessageType, reqHandler func([]byte) []byte) {
p.RegisterMsgHandler(msgType, handlerFromBytesHandler(reqHandler))
}
// SendRequest sends a request of a specific message.
func (p *MessageServer) SendRequest(msgType MessageType, payload []byte, address p2pcrypto.PublicKey, resHandler func(msg []byte)) error {
reqID := p.newReqID()
p.pendMutex.Lock()
p.resHandlers[reqID] = resHandler
p.pendingQueue.PushBack(Item{id: reqID, timestamp: time.Now()})
p.pendMutex.Unlock()
msg := &service.DataMsgWrapper{Req: true, ReqID: reqID, MsgType: uint32(msgType), Payload: payload}
if sendErr := p.network.SendWrappedMessage(address, p.name, msg); sendErr != nil {
p.With().Error("sending message failed",
log.Uint32("msg_type", uint32(msgType)),
address.Field("recipient"),
log.Int("msglen", len(payload)),
log.Err(sendErr))
p.removeFromPending(reqID)
return sendErr
}
p.Log.With().Debug("sent request", log.Uint64("request_id", reqID))
return nil
}
func (p *MessageServer) newReqID() uint64 {
return atomic.AddUint64(&p.ReqID, 1)
}