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Brief Overview

I have a turn-based web app that puts a 60 second limit per turn, unless they end their turn before 60 seconds, whereby the next user's turn begins.

It works by preventing the production of data on the PHP page by way of a while statement which checks for new data, produces it if it exists, or sleeps and resets if it doesn't:

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

I got this concept from these StackOverflow questions:

How do I implement basic "Long Polling"?

Ajax push system

Issue

However, once the callout begins, the page becomes relatively unresponsive; doing something simple such as refreshing the page will not work until the timeout is complete or new data is received.

How can I configure this code so that the page remains responsive while awaiting new data?

AJAX/jQuery code

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 Code

<?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)));
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Ben
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  • session_write_close() is most likely your issue. I would put it outside before the while loop like right after your variables. Also see this comment. http://php.net/manual/en/function.session-write-close.php#96982 – Panama Jack Sep 29 '15 at 16:33

1 Answers1

2

If you opened a session with session_start() better close it with session_write_close() before you start waiting, or access to the session will be blocked in all other requests.

<?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)));
developerwjk
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