How do I observe a rate Limit in PHP? - php

Question

So, I'm requesting data from an API.
So far, my API key is limited to:
10 requests every 10 seconds
500 requests every 10 minutes
Bascially, I want to request a specific value from every game the user has played.
That are, for example, about 300 games.
So I have to make 300 requests with my PHP. How can I slow them down to observe the rate limit?
(It can take time, site does not have to be fast)
I tried sleep(), which resulted in my script crashing.. Any other ways to do this?

Answer 1

I suggest setting up a cron job that executes every minute, or even better use Laravel scheduling rather than using sleep or usleep to imitate a cron.
Here is some information on both:
https://laravel.com/docs/5.1/scheduling
http://www.cyberciti.biz/faq/how-do-i-add-jobs-to-cron-under-linux-or-unix-oses/

Answer 2

This sounds like a perfect use for the set_time_limit() function. This function allows you to specify how long your script can execute, in seconds. For example, if you say set_time_limit(45); at the beginning of your script, then the script will run for a total of 45 seconds. One great feature of this function is that you can allow your script to execute indefinitely (no time limit) by saying: set_time_limit(0);.
You may want to write your script using the following general structure:
<?php
// Ignore user aborts and allow the script
// to run forever
ignore_user_abort(true);
set_time_limit(0);
// Define constant for how much time must pass between batches of connections:
define('TIME_LIMIT', 10); // Seconds between batches of API requests
$tLast = 0;
while( /* Some condition to check if there are still API connections that need to be made */ ){
if( timestamp() <= ($tLast + TIME_LIMIT) ){ // Check if TIME_LIMIT seconds have passed since the last connection batch
// TIME_LIMIT seconds have passed since the last batch of connections
/* Use cURL multi to make 10 asynchronous connections to the API */
// Once all of those connections are made and processed, save the current time:
$tLast = timestamp();
}else{
// TIME_LIMIT seconds have not yet passed
// Calculate the total number of seconds remaining until TIME_LIMIT seconds have passed:
$timeDifference = $tLast + TIME_LIMIT - timestamp();
sleep( $timeDifference ); // Sleep for the calculated number of seconds
}
} // END WHILE-LOOP
/* Do any additional processing, computing, and output */
?>
Note: In this code snippet, I am also using the ignore_user_abort() function. As noted in the comment on the code, this function just allows the script to ignore a user abort, so if the user closes the browser (or connection) while your script is still executing, the script will continue retrieving and processing the data from the API anyway. You may want to disable that in your implementation, but I will leave that up to you.
Obviously this code is very incomplete, but it should give you a decent understanding of how you could possibly implement a solution for this problem.

Answer 3

Don't slow the individual requests down.
Instead, you'd typically use something like Redis to keep track of requests per-IP or per-user. Once the limit is hit for a time period, reject (with a HTTP 429 status code, perhaps) until the count resets.
http://redis.io/commands/INCR coupled with http://redis.io/commands/expire would easily do the trick.