backup, reddit post.

file.txt

Some context : 
I need to do instant push notifications with one-signal when someone posts a comment, and I must ensure there's no compromise on the speed, it seems to add to the load time from 1 device to 5 devices receiving notifications, and gets slower and slower as I'm going to 100 devices, because of the way these tokens work, a user could artifically get 1000s of device tokens in onesignal ( assumption ), cleaning them up trough a cron job would be another thing I'll tackle, but later ( if someone gets here with similar requirements, a heads up )
I'm looking for suggestions, or weak points in my logic, if anyone ever encountered this, or simply want to talk about it, maybe there's a better way of approaching this, or WP Core has something better available.
Why I want to use an Async Request : 
I can't work with cron jobs, because I want this to happen instantly, I'm essentially turning 1 POST request into another GET request, my other option would be to have an infinite loop somewhere always happening, and I don't know yet if that will work better than this, there might be a sweet spot somewhere, where that might run fast, and more effective.
Architecture Details : 
- There will always be an action_alias ( something to identify what needs to run ) in there.
- There will always be atleast an ID in every request, if there isn't one, it's better off as a cron job most likely.
- I want this to be secure from abusing, I've went with a simple solution, md5( NONCE_SALT . $action . $id ) is my security token, and artificially creating them is impossible if someone does not know the NONCE_SALT, which in itself would be an entirelly different problem
---
I've decided to do a non-blocking HTTP Request, eventually I've reached this code : 
wp_remote_get( $url, [
 'timeout'   => 0.01,
 'blocking'  => false,
 'sslverify' => false
] );
The class that handles everything, is this one : 
class IUA {

  /**
   * @var IUA
   */
  protected static $instance;

  /**
   * @return IUA
   */
  public static function instance() {
    if (!isset(self::$instance))
      self::$instance = new self();

    return self::$instance;
  }

  private $_callbacks = [];

  public function setup() {
    if( !defined( 'MY_PREFIX_IGNORE_USER_ABORT_REQUEST' ) || !MY_PREFIX_IGNORE_USER_ABORT_REQUEST )
      return;

    if( md5( NONCE_SALT . $_GET[ 'action' ] . $_GET[ 'id' ] ) !== $_GET[ 'secure' ] )
      exit;

    add_action( "init", [ $this, '_init' ], 50 );
  }

  public function _init() {
    if( !isset( $this->_callbacks[ $_GET[ 'action' ] ] ) )
      exit;

    $request_data = $_GET;

    unset( $request_data[ 'action' ] );
    unset( $request_data[ 'secure' ] );

    call_user_func( $this->_callbacks[ $_GET[ 'action' ] ], $request_data );
    exit;
  }

  public function register( $alias, $callback ) {
    $this->_callbacks[ $alias ] = $callback;
  }

  public function request( $action, $id, $request_data = [] ) {
    $url = MY_PLUGIN_BASE_URL_PATH . '/ignore-user-abort.php';
    $url = add_query_arg( 'action', $action, $url );
    $url = add_query_arg( 'id', $id, $url );
    $url = add_query_arg( 'secure', md5( NONCE_SALT . $action . $id ), $url );

    if( is_array( $request_data ) && !empty( $request_data ) )
      foreach( $request_data as $key => $value )
        $url = add_query_arg( $key, $value, $url );

    wp_remote_get( $url, [
      'timeout'   => 0.01,
      'blocking'  => false,
      'sslverify' => false
    ] );
  }

}
The URL is pointing to a file called ignore-user-abort.php which is located in the plugin file.
Now, because I don't know how to safely get to the central index.php file, I've went ahead and came up with a hack, sort-off, this is the part I'm actually most concerned about, seems to work.
File : ignore-user-abort.php
// The 3 core parameters of this functionality, it is intended to be used async in PHP, and do extensive requests without stopping the user request.
// An ID is central for any action, and we'll use it to add a security layer to the request.

ignore_user_abort( true );

if( !isset( $_GET[ 'action' ] )
    || !isset( $_GET[ 'id' ] )
    || !isset( $_GET[ 'secure' ] ) )
 exit;

$dirname = dirname( __FILE__ );

while( $dirname !== '/' ) {
 // We aim to find the wp-login.php, as the wp-config could be hidden on certain hosts, and we're aiming for the index.php either way.
 if( file_exists( $dirname . '/wp-login.php' ) )
 break;

 $dirname = dirname( $dirname );
}

if( $dirname === '/' && !file_exists( $dirname . 'wp-login.php' ) )
 exit;

if( !file_exists( rtrim( $dirname, '/' ) . '/index.php' ) )
 exit;

define( "MY_PREFIX_IGNORE_USER_ABORT_REQUEST", true );

require_once( rtrim( $dirname, '/' ) . '/index.php' );
exit;
To register an async request :
IUA::instance()->register( 'push_one_signal', [ $this, '_iua_push_notifications' ] );
To Trigger an async request :
IUA::instance()->request( 'push_one_signal', $my_id );
Discarded Ideas : 
- I've initially wanted to hook directly into the wp-cron.php, but seems risky, as it would fail if a cron job is running, or can potentially mess up with the cron jobs.
- Initially wanted to rely on add_action & do_action & has_action, but I've decided that I might need more than an alias later, and went for the function.

Thank you