Handle inter-process communication between PhantomJS and Golang processes via hixie-76 websockets

    Although PhantomJS version 1.9 does have WebSocket support, that support is limited to the hixie-76 draft of the protocol. PhantomJS 2.0 is scheduled to include the more modern RFC 6455 version of WebSockets. When writing scripts for PhantomJS that intend to use WebSocket connections, we must ensure that the server supports the hixie-76 version of the protocol.

package main

import (
	"bufio"
	"code.google.com/p/go.net/websocket"
	"github.com/garyburd/redigo/redis"
	//"github.com/davecgh/go-spew/spew"
	"crypto/md5"
	"encoding/hex"
	"io"
	"net/http"
	"os"
	"strconv"
	"strings"
	"time"
)

const PS = string(os.PathSeparator)
const PH = "/"

var (
	pwd, _        = os.Getwd()
	JSON          = websocket.JSON
	Message       = websocket.Message
	ActiveClients = make(map[ClientConn]int64)
	redis_host    string
	rdPool        *redis.Pool
	Upload_Dir    string
)

type ClientConn struct {
	websocket *websocket.Conn
	clientIP  string
}

func init() {
	f, err := os.Open("config")

	if err != nil {
		panic(err)
	} else {
		defer f.Close()
	}

	buf := bufio.NewReader(f)

	line, err := buf.ReadString('\n')
	if err != nil || io.EOF == err {
		panic(err)
	} else {
		redis_host = strings.TrimSpace(line)
		rdPool = initRedis(redis_host)
	}

	line, err = buf.ReadString('\n')
	if err != nil || io.EOF == err {
		panic(err)
	} else {
		Upload_Dir = strings.TrimSpace(line)
	}
}

func SockServer(ws *websocket.Conn) {
	var err error
	var clientMessage string
	var serverMessage string

	defer func() {
		if err = ws.Close(); err != nil {
			pp("Websocket could not be closed", err.Error())
		}
	}()

	client := ws.Request().RemoteAddr
	pp("Client connected:", client)
	sockClient := ClientConn{ws, client}
	ActiveClients[sockClient] = time.Now().Unix()
	pp("Number of clients connected:", len(ActiveClients))

	for {
		err = Message.Receive(ws, &clientMessage)
		if err != nil {
			pp("Websocket Disconnected waiting", err.Error())
			delete(ActiveClients, sockClient)
			pp("Number of clients still connected:", len(ActiveClients))
			clientMessage = ""
			return
		} else {
			if clientMessage == "GET" {
				ret, err := redis.Strings(RedisExec(rdPool.Get(), "BLPOP", "screenshot:queue", 30))
				if len(ret) == 2 && err == nil {
					url := ret[1]

					h := md5.New()
					h.Write([]byte(url))
					name := hex.EncodeToString(h.Sum(nil))

					subDir := strconv.Itoa(time.Now().Year()) + PS + strconv.Itoa(int(time.Now().Month()))
					os.MkdirAll(Upload_Dir+subDir, 0777)
					filename_full := Upload_Dir + subDir + PS + name

					serverMessage = filename_full + "|" + url

					pp("pop queue ok.", client, serverMessage)
					if err = Message.Send(ws, serverMessage); err != nil {
						pp("Could not send message to ", client, err.Error())
					}
				} else {
					p("pop queue error.", client, err.Error())
					if err = Message.Send(ws, "NULL"); err != nil {
						pp("Could not send message to ", client, err.Error())
					}
				}
			} else if clientMessage == "OPEN" {
				if err = Message.Send(ws, "OPEN"); err != nil {
					pp("Could not send message to ", client, err.Error())
				}
			} else {
				//todo
			}
			clientMessage = ""
		}
	}
}

func main() {
	http.Handle("/socket", websocket.Handler(SockServer))
	err := http.ListenAndServe("127.0.0.1:9527", nil)
	if err != nil {
		panic("ListenAndServe: " + err.Error())
	}
}

phantomjs起多进程的，做一个服务器端screenshot的service非常简单，关键部分代码如下：

var page = require('webpage').create(),
    system = require('system'),
    address, output, size;

var loop = function() {
	var ws = new WebSocket("ws://127.0.0.1:9527/socket");
	ws.onopen = function(evt){
		ws.send('OPEN');
		//ws.send('GET');
		console.log("Opened.");
	};
	ws.onclose = function(evt){
		console.log("Closed.");
		window.setTimeout(loop, 60000);
	};
	ws.onmessage = function(evt){
		console.log("Message:"+ evt.data);
		//ws.send(evt.data);
		if(evt.data!= "" && evt.data!= "OPEN"){
			arr= evt.data.split('|');
			if (arr.length== 2){
				name= arr[0]+ ".png";
				url= arr[1];
				screenshot(url, name, "");
			}			
		}
		ws.send('GET');		
	};
	ws.onerror = function(evt){
		console.log("Error." + evt.data);
	};
};

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