clienthub.go

// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package streaming

import (
	"bytes"
	"net/http"
	"time"

	"github.com/gorilla/websocket"
	log "github.com/sirupsen/logrus"
)

const (
	// Time allowed to write a message to the peer.
	writeWait = 10 * time.Second

	// Time allowed to read the next pong message from the peer.
	pongWait = 60 * time.Second

	// Send pings to peer with this period. Must be less than pongWait.
	pingPeriod = (pongWait * 9) / 15

	// Maximum message size allowed from peer.
	maxMessageSize = 4096
)

var (
	newline = []byte{'\n'}
	space   = []byte{' '}
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
}

// Client is a middleman between the websocket connection and the hub.
type Client struct {
	hub *ClientHub

	// The websocket connection.
	conn *websocket.Conn

	// Buffered channel of outbound messages.
	send chan []byte

	clientId string
}

// readPump pumps messages from the websocket connection to the hub.

// The application runs readPump in a per-connection goroutine. The application
// ensures that there is at most one reader on a connection by executing all
// reads from this goroutine.
func (c *Client) readPump() {
	defer func() {
		c.hub.Unregister <- c
		c.conn.Close()
	}()
	c.conn.SetReadLimit(maxMessageSize)
	c.conn.SetReadDeadline(time.Now().Add(pongWait))
	c.conn.SetPongHandler(func(string) error { c.conn.SetReadDeadline(time.Now().Add(pongWait)); return nil })
	for {
		_, message, err := c.conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
				log.Printf("error: %v", err)
			}
			break
		}
		message = bytes.TrimSpace(bytes.Replace(message, newline, space, -1))
		c.hub.Broadcast <- message
	}
}

// writePump pumps messages from the hub to the websocket connection.
//
// A goroutine running writePump is started for each connection. The
// application ensures that there is at most one writer to a connection by
// executing all writes from this goroutine.
func (c *Client) writePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		c.conn.Close()
	}()
	for {
		select {
		case message, ok := <-c.send:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if !ok {
				// The hub closed the channel.
				c.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}

			w, err := c.conn.NextWriter(websocket.TextMessage)
			if err != nil {
				return
			}
			w.Write(message)

			// Add queued chat messages to the current websocket message.
			n := len(c.send)
			for i := 0; i < n; i++ {
				w.Write(newline)
				w.Write(<-c.send)
			}

			if err := w.Close(); err != nil {
				return
			}
		case <-ticker.C:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				return
			}
		}
	}
}

// ServeWs handles websocket requests from the peer.
func ServeWs(hub *ClientHub, w http.ResponseWriter, r *http.Request) {
	upgrader.CheckOrigin = func(r *http.Request) bool { return true }
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println(err)
		return
	}

	client := &Client{
		hub:  hub,
		conn: conn,
		send: make(chan []byte, 256),
	}
	hub.Register <- client

	// Allow collection of memory referenced by the caller by doing all work in
	// new goroutines.
	go client.writePump()
	go client.readPump()
}

// ClientHub maintains the set of active clients and broadcasts messages to the
// clients.
type ClientHub struct {
	// Registered clients.
	Clients map[*Client]bool

	// Updates to be broadcasted to the clients.
	Broadcast chan []byte

	// Updates to be sent to a single user.
	Send chan *ClientMessage

	// Register requests from the clients.
	Register chan *Client

	// Unregister requests from clients.
	Unregister chan *Client
}

type ClientMessage struct {
	ClientId string
	Message  []byte
}

func NewClientHub() *ClientHub {
	return &ClientHub{
		Broadcast:  make(chan []byte),
		Send:       make(chan *ClientMessage),
		Register:   make(chan *Client),
		Unregister: make(chan *Client),
		Clients:    make(map[*Client]bool),
	}
}

func (h *ClientHub) Run() {
	for {
		select {
		case client := <-h.Register:
			h.Clients[client] = true
		case client := <-h.Unregister:
			if _, ok := h.Clients[client]; ok {
				delete(h.Clients, client)
				close(client.send)
			}
		case message := <-h.Broadcast:
			for client := range h.Clients {
				select {
				case client.send <- message:
				default:
					close(client.send)
					delete(h.Clients, client)
				}
			}
		case clientMessage := <-h.Send:
			for client := range h.Clients {
				if client.clientId == clientMessage.ClientId {
					select {
					case client.send <- clientMessage.Message:
					default:
						close(client.send)
						delete(h.Clients, client)
					}
				}
			}
		}
	}
}