轮询与长轮询
一、轮询
前端通过定时器每隔多少秒钟发送一次请求。
投票示例：
app.py
from flask import Flask,render_template,request,jsonify app = Flask(__name__) USERS = { '1':{'name':'贝贝','count':1}, '2':{'name':'小东北','count':0}, '3':{'name':'何伟明','count':0}, } @app.route('/user/list') def user_list(): return render_template('user_list.html',users=USERS) @app.route('/vote',methods=['POST']) def vote(): uid = request.form.get('uid') USERS[uid]['count'] += 1 return "投票成功" @app.route('/get/vote',methods=['GET']) def get_vote(): return jsonify(USERS) if __name__ == '__main__': # app.run(host='192.168.13.253',threaded=True) app.run(threaded=True)
user_list.html
<!DOCTYPE html> <html lang="zh-CN"> <head> <meta charset="UTF-8"> <title>Title</title> <meta name="viewport" content="width=device-width, initial-scale=1"> <style> li{ cursor: pointer; } </style> </head> <body> <ul id="userList"> {% for key,val in users.items() %} <li uid="{{key}}">{{val.name}} ({{val.count}})</li> {% endfor %} </ul> <script src="https://cdn.bootcss.com/jquery/3.3.0/jquery.min.js"></script> <script> $(function () { $('#userList').on('dblclick','li',function () { var uid = $(this).attr('uid'); $.ajax({ url:'/vote', type:'POST', data:{uid:uid}, success:function (arg) { console.log(arg); } }) }); }); /* 获取投票信息 */ function get_vote() { $.ajax({ url:'/get/vote', type:"GET", dataType:'JSON', success:function (arg) { $('#userList').empty(); $.each(arg,function (k,v) { var li = document.createElement('li'); li.setAttribute('uid',k); li.innerText = v.name + "(" + v.count + ')' ; $('#userList').append(li); }) } }) } setInterval(get_vote,3000); //每隔3s中获取一次投票信息 </script> </body> </html>
二、长轮询
浏览器发送一次请求过来会让浏览器hang住，最多hang住30s,如果在这一段时间没人发数据让浏览器等30s然后释放，如果在此期间有人发数据了就会立即拿到结果然后返回给用户，实现了结果实时返回，省去了连接的次数。兼容性好、实时、在线。
app1.py
from flask import Flask,render_template,request,jsonify,session import uuid import queue app = Flask(__name__) app.secret_key = 'asdfasdfasd' USERS = { '1':{'name':'贝贝','count':1}, '2':{'name':'小东北','count':0}, '3':{'name':'何伟明','count':0}, } QUEQUE_DICT = { # 'asdfasdfasdfasdf':Queue() } @app.route('/user/list') def user_list(): user_uuid = str(uuid.uuid4()) #用户登录成功的时候为每个人生成一个uuid QUEQUE_DICT[user_uuid] = queue.Queue() #以uuid为key，为每个人创建一个queue session['current_user_uuid'] = user_uuid #把用户的uuid放入session中，session默认放入加密的cookie中 return render_template('user_list.html',users=USERS) #投票 @app.route('/vote',methods=['POST']) def vote(): uid = request.form.get('uid') #获取用户uid USERS[uid]['count'] += 1 #票数加1 for q in QUEQUE_DICT.values(): # q.put(USERS) # return "投票成功" #获取票数 @app.route('/get/vote',methods=['GET']) def get_vote(): user_uuid = session['current_user_uuid'] #去cookie中获取之前放入的uuid q = QUEQUE_DICT[user_uuid] #根据user_uuid获取q ret = {'status':True,'data':None} # try: users = q.get(timeout=5) # ret['data'] = users # except queue.Empty: ret['status'] = False # return jsonify(ret) # if __name__ == '__main__': # app.run(host='192.168.13.253',threaded=True) # app.run(threaded=True) #
user_list.html
<!DOCTYPE html> <html lang="zh-CN"> <head> <meta charset="UTF-8"> <title>Title</title> <meta name="viewport" content="width=device-width, initial-scale=1"> <style> li{ cursor: pointer; } </style> </head> <body> <ul id="userList"> {% for key,val in users.items() %} <li uid="{{key}}">{{val.name}} ({{val.count}})</li> {% endfor %} </ul> <script src="https://cdn.bootcss.com/jquery/3.3.0/jquery.min.js"></script> <script> $(function () { $('#userList').on('click','li',function () { var uid = $(this).attr('uid'); $.ajax({ url:'/vote', type:'POST', data:{uid:uid}, success:function (arg) { console.log(arg); } }) }); get_vote(); //当页面框架加载成功时，立即获取投票信息 }); /* 获取投票信息 */ function get_vote() { $.ajax({ url:'/get/vote', type:"GET", dataType:'JSON', success:function (arg) { if(arg.status){ $('#userList').empty(); $.each(arg.data,function (k,v) { var li = document.createElement('li'); li.setAttribute('uid',k); li.innerText = v.name + "(" + v.count + ')' ; $('#userList').append(li); }) } get_vote(); //没人投票，发送请求 ---递归 } }) } </script> </body> </html>
