Recently, I was tasked with diagnosing why emails sent by a web application to a company internal email address were not always arriving in the inbox. This internal email was hosted on Google Apps, which has a receiving rate limit of 60 per minute. Any emails that exceed the quota are dropped, though the documentation says they are bounced. THIS IS A LIE!
To solve this problem, I used Laravel event listeners and the magic of @antirez’s Redis.
Add the following events to your app/Providers/EventServiceProvider.php file’s listen array.
<?php
protected $listen = [
...
\Illuminate\Mail\Events\MessageSent::class => [
\App\Listeners\MessageSent::class,
],
\Illuminate\Mail\Events\MessageSending::class => [
\App\Listeners\MessageSending::class,
],
...
];The MessageSent listener will use Redis to count the number of messages sent.
The current minute is stored as part of the redis key.
When a new minute starts, a new key will be used.
To prevent the keys from overlapping to the next hour, an expiration value is set to 30 minutes.
<?php
namespace App\Listeners;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Contracts\Queue\ShouldQueue;
class MessageSent
{
public function __construct()
{
//
}
public function handle($event)
{
$key = self::getCounterKey();
// 30 minute cache time
$ttl = 60 * 30;
// Create new redis key every minute with count
\Redis::incr($key);
// Set expiration so these keys die after they are no longer needed
\Redis::expire($key, $ttl);
}
public static function getCounterKey(): string
{
return "mailcounter:" . date('i');
}
}The MessageSending event runs before an email gets sent and is where the rate limiting actually occurs.
This event can be tuned to fit your needs.
<?php
namespace App\Listeners;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Contracts\Queue\ShouldQueue;
class MessageSending
{
public function __construct()
{
//
}
public function handle($event)
{
// Threshhold number of messages before limiting occurs
$threshhold = 45;
// Number of seconds to sleep before sending.
// Dev environments don't need to sleep (presumably)
$sleep = \App::environment('production') ? 5 : 0;
// Get the number of emails sent this minute
$count = (int)\Redis::get(MessageSent::getCounterKey());
// If more than 45 messages have been sent this minute, then we will sleep for 5 seconds.
// This will prevent us from exceeding the 60 email/minute limit on our distribution lists.
if ($count > $threshhold) {
sleep($sleep);
}
}
}