Shared memory between requests

[bertbijnens]

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Content

For a high performance application I need shared memory between workers, and between multiple instances.
In my example I'm using a simple counter.

After a quick test I notice that (within requests), both the array cache driver and static properties are a working method of achieving this.
I need to update this counter regularly using a Redis pub/sub connection.
I setup a Listener object, registered it in the listener.php config and update the field using cache, updating a static variable, but both do not work.

Controller:

<?php

declare(strict_types=1);

namespace App\Http\Controllers;

use Hypervel\Http\Request;

class ExampleController extends AbstractController
{
    public static $index = 0;

    public function index(Request $request): array
    {
        return response()->json([
            'index' => self::$index++,
            'context' => cache()->get('counter')
        ]);
    }
}

Inside listener with Hyperf\Framework\Event\OnStart event:

 /**
    * @param OnStart $event
    */
   public function process(object $event): void
   {
       Redis::subscribe(['test-channel'], function (string $counter) {
           cache()->set('counter', intval($counter));
           app(CounterService::class)->counter = intval($counter);
           ExampleController::$index = intval($counter);
       });
   }

The redis process can keep track of the counter. But the requests can't.
It looks like all the requests across the workers have shared memory, but the OnStart event is triggered in another process with it's own memory.

What's the best way to insert this counter property in the memory of the worker processes?

[albertcht]

Not sure about the purpose of the design in your demo code.
If you're looking for something related to multi-tier cache, you can refer to: https://hypervel.org/docs/cache#building-cache-stacks

Workers don't share the memory. You should take a look about how it works in Swoole:

• https://openswoole.com/how-it-works
• https://openswoole.com/docs/modules/swoole-server-on-start

[bertbijnens]

Hi @albertcht,

Thanks for the reply.

In short: I need to cache properties in a high performance local cache or memory cache using a Redis pub/sub connection. With the cache being in memory. I guess I could use swoole tables cache for this.

I'm working on a high traffic queue. I will receive about 100.000 requests tot my store in a few seconds. I need to assign them an incremental id (or timestamp) while keeping count of how many people are trying to get in my store.
These visitors will then be put in a queue, where every few seconds a number of visitors are allowed into the store.
This functionality will exist in a kubernetes environment with multiple pods to serve this single purpose.

It's not important that the incremental id's are shared across multiple pods, but it would be very nice if they were incremental across workers within the same pod.
When a run php artisan server or php artisan start, and test this locally, the static variables are shared between requests. Benchmarking this call with 100.000 calls, end up with counter on exactly 100.000.
So it looks like this static variable is shared across workers, or only one of my 12 workers are being used.

In the background I want to sync statistics, settings and the state of the queue between multiple kubernetes pods using redis pub/sub, but only one connection for each pod and not one connection for each worker. This connection could then update the necessary static counters or using a singleton or array cache.

[albertcht]

Hi @bertbijnens , like what I mentioned above, global variables are not shared in different workers. You need to use Swoole table or atomic counter for that purpose.