javascript - "Long Polling"模拟撑起整个网页

Question

简要概述

我有一个基于回合的网络应用程序，每回合限制 60 秒，除非他们在 60 秒之前结束回合，从而下一个用户的回合开始。

它的工作原理是通过 while 语句来阻止 PHP 页面上生成数据，该语句检查新数据，如果存在则生成数据，如果不存在则休眠并重置:

while($olddata === $newdata){
    sleep(2);
    /* get new data and repeat */
}

我从这些 StackOverflow 问题中得到了这个概念:

How do I implement basic "Long Polling"?

Ajax push system

问题

但是，一旦标注开始，页面就会变得相对无响应；在超时完成或收到新数据之前，执行一些简单的操作(例如刷新页面)将不起作用。

如何配置此代码，以便页面在等待新数据时保持响应？

AJAX/jQuery 代码

function draftPing(){
    //This $holder element holds the data including the
    //row ID, which is used to determine which turn number
    //we are on
    var $holder = $("#data-holder");
    var currID = $holder.attr("data-currID");

    $.ajax({
        type: "POST",
        url: "../inc/draft-ping.php",
        data: { currID : currID },
        async: true,
        cache: false,
        timeout: 60000,
        success: function(data) {
            var jsonData = $.parseJSON(data);

            //Update $holder with new turn ID
            $holder.attr("data-currID", jsonData[0]);

            /* Do stuff with data */
            updateDeadline(jsonData[1]);
            updateTeam(jsonData[3]);
            updateDraft(jsonData[4]);

            /* Begin the next call for new information (wait 1s)*/
            setTimeout(
                draftPing,
                1000
            );
        },
        error: function(XMLHttpRequest, textStatus, errorThrown) {
            alert("Draft retrieve error: ", textStatus + " (" + errorThrown + ")");
            setTimeout(
                draftPing, /* Try again after 5s*/
                5000);
        }
    });
}

PHP 代码

<?php

session_start();
require_once("../config.php");
require_once("classes.php");
require_once("functions.php");

$postedID = $_POST["currID"];
$draft = new Draft($user->getLeagueID());
$currID = $draft->getCurrDraftRow();

//This is the "long polling" simulation...
//the AJAX callback won't produce any information
//until the current ID is different to the ID
//on the page with the AJAX post function
while($currID == $postedID){
    sleep(2);
    $currID = $draft->getCurrDraftRow();
}

/* Get all the data - redacted because it's not important (and it works) */

//Output all the data as one JSON object
exit(json_encode(array($nid, $ndeadline, $nuserid, $fteam, $fdraft)));

Answer 1

如果您使用 session_start() 打开 session ，最好在开始等待之前使用 session_write_close() 关闭它，否则所有其他请求对 session 的访问都将被阻止.

<?php

session_start();
require_once("../config.php");
require_once("classes.php");
require_once("functions.php");

$postedID = $_POST["currID"];
$draft = new Draft($user->getLeagueID());
$currID = $draft->getCurrDraftRow();

//This is the "long polling" simulation...
//the AJAX callback won't produce any information
//until the current ID is different to the ID
//on the page with the AJAX post function
while($currID == $postedID){
    session_write_close(); //added
    sleep(2);
    session_start(); //if needed, doesn't look like it is though
    $currID = $draft->getCurrDraftRow();
}

/* Get all the data - redacted because it's not important (and it works) */

//Output all the data as one JSON object
exit(json_encode(array($nid, $ndeadline, $nuserid, $fteam, $fdraft)));