长轮询实现消息推送

/**
 *pns模型层
 *@constructs M2012.Model.Pns.PnsModel
 *@extends Backbone.Model
 *@example
 *new M2012.Model.Pns().startRequestPns();
 */
M139.namespace("M2012.Model.Pns", {
    PnsModel : Backbone.Model.extend({
        callApi : M139.RichMail.API.call,
        pnsUrl : ‘/pns/poll?sid=‘ + top.sid + ‘&comeFrom=1003‘, // PNS接口地址负责推送消息到前端
        pnsErrorInterval : 1000 * 120, // 接口报错后下一次重新调接口的时间间隔
        pnsTimer : null, // 接口报错后需要用定时器再调一次接口，pnsTimer用于报错定时器ID
        msgTypes : {//pns推送过来的消息类型
            mailMsg : 70
        },
        logger : new top.M139.Logger({
            name : "M2012.Model.Pns"
        }),
        initialize : function() {
            $App.registerModel("pnsModel", this);
        },

        startRequestPns : function() {
            var self = this;

            var options = {};
            options.method = ‘get‘;
            options.timeout = self.pnsErrorInterval;
            options.error = function() {
                self.callPns();
                self.logger.error("newMailArrival callPns error");
            };
            options.ontimeout = function() {
                self.callPns();
                self.logger.error("newMailArrival callPns timeout");
            };
            options.isSendClientLog = false;

            M139.RichMail.API.call(self.pnsUrl, null, function(e) {
                var result = e.responseData;
                if (result) {
                    console.log(result);
                    if (result.errorCode) {
                        self.callPns();
                        self.logger.error("newMailArrival returndata error", "[pns/poll]", result);
                    } else {
                        self.pnsResultHandle(result);
                        $App.trigger("pnsNewArrival", result);
                        //留给以后扩展
                        self.callPns(500);
                        //self.autoReceiveMail();
                    }
                } else {
                    self.callPns();
                    self.logger.error("newMailArrival returndata error", "[pns/poll]", result);
                }
            }, options);
        },

        callPns : function(seconds) {
            var self = this;

            // 判断用户是否登录超时
            if (top.$App.isSessionOut()) {
                console.log(‘登录超时！不再请求PNS‘);
                return;
            }

            if (self.pnsTimer) {
                clearTimeout(self.pnsTimer);
            }
            self.pnsTimer = setTimeout(function() {
                self.startRequestPns();
            }, seconds || self.pnsErrorInterval);
        },

        /*
         * 此函数可用于单元测试
         * $App.getModel("pnsModel").pnsResultHandle({});
         */
        pnsResultHandle : function(result) {
            var self = this;
            if (result.c > 0) {//c代表数量
                var msgArr = result.msg;
                for (var i = 0, l = msgArr.length; i < l; i++) {
                    // TODO 根据消息类型处理业务逻辑
                }
            } else if (result.c == 0) {
                console.log(‘超时返回！autoReceiveMail‘);
            }
        }
    })
});