Display WAITING on webpage using PHP Ajax & mysql

that's how i'd do it - poll the server every N seconds just like you say.

The system im developing may have 100 browsers all on the waiting page at the same time.
This would mean 100 browsers all polling the mysql db every second.

Is there a better way of doing this?

I have been looking into LONG POLLING but dont quite understand it yet. Would this be the way to go? How different is this to a standard ajax call??

Steve

yes, i think every 1 second is a lot (which is why I said every "N" seconds), but you know your data and maybe you need that kind of instant feedback.

i have looked into this from time to time in the past and always ended up sticking with polling... server push / comet / long polling whatever you want to call it always involved leaving the connection permanently open... so instead of ever N seconds you have this connected open permanently.

if you could increase the interval you will reduce the load

in the past we have looked at how the page design can aid in perceived performance - rather than a loading screen where the user has nothing to read or do can you present the user with some reading (voting instructions or something)...
or failing that give them a quote of the day, pacman game etc :)

my last solution could poll easily for 20 seconds (slow service call) so we put the region that would be updated at the bottom of a screen which would take the user a minute to work through - they wouldn't even notice the slow service call.

The system im designing needs to start the voting for possibly 100 browsers at the same time (or within a fraction of a second).

From what ive read, the system may work like this...
What do you think?
JS

    function waiting(){
        $.ajax({
            type: "GET",
            url: "waiting.php",
            async: true,
            cache: false,
            timeout:300000, /* Timeout in ms */

            success: function(data){
                                if (data == 1){
                                            load vote question
                                 }
                                 else
                                 {
 				            $.blockUI();  /*  display please wait*/
                                            waiting()', /* Try again */
                                 }
            },
        });
    };

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PHP

connect to db
$wait = 0
while $wait = 0 {
           query database
           sleep(1);
}
echo $wait

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