PHP多个脚本排队？

Question

I have an html which run a php several times (about 20). Something like

for(i=0;i<20; i++){
$.get('script.php?id='+i,function(){...});
}

Every time the script runs, it get some content through different websites (every time a different one), so each script takes from 1 to 10 seconds to complete and give a response. I want to run all the script simultaneously to be faster, but 2 things makes it slow: the first is on the html page, it seems that ajax requested are queued after first five, at least chrome developer said me that... (this can be fixed easily I think, I've not bothered yet to find a solution); the second thing is on php side: even if the first 5 scripts are triggered together, they are run sequentially, not even in order. I 've put some

echo microtime(true);

around the script to get wherever the script is slow and what I found out (a bit surprised) is that the time on the beginning of the script (the one which should be run at almost the same time on all script) is different: the difference is very consistent, also 10 seconds, like if the second script wait the first to end before begin. How can I have all the script be running together at the same time? Thank you.

Answer 1

I very frankly advise that you should not attempt anything "multi-threaded" here, "nor particularly 'fancy.'"

Design your application to have some kind of queue (it can be a simple array) of "things that need to be done." Then, issue "some n" number of initial AJAX requests: certainly no more than 3 to 5.

Now, wait for notification that each request has succeeded or failed. After somehow recording the status of the request, de-queue another request and start it.

In this way, "n requests, but no more than n requests," will be active at any one time, and yes, they will each take a different amount of time, "but nobody cares."

"JavaScript is not multi-threaded," and we have no need for it. Everything is done by events, which are handled one at a time, and that happens to work beautifully.

Your program runs until the queue is empty and all of the outstanding AJAX requests have been completed (or, have failed).

There's absolutely no advantage in "getting too fancy" when the requests that you are performing might each take several seconds to complete. There's also no particular advantage in trying to queue-up too many TCP/IP network requests. Predictable Simplicity, in this case, will (IMHO) rule the day.