Abort AJAX request

Question

I have a question. I need to cancel an AJAX request on the client side and the server side.

On the client side I use the abort()

var requisicao = $.ajax({ url : 'xyz.php'  });

if(requisicao && cliente_abortou_requisicao){ 
    requisicao.abort(); 
}

Now on the server side I’m doubtful. How do I stop PHP from running? Because if I only do it on the client side, script still runs on the server and if I make another AJAX request to the server this request is waiting for the end of the previous request.

Example:

 <?php

      $DB = getConexaoOracle();

      $sql = "SELECT * FROM FUNCIONARIOS"; // 1 milhão de registros (exemplo)
      $RS = $DB->Execute($sql);

      $array_de_retorno = array();

      while($RS->hasNext()){
            ...
      }

      die(json_encode($array_de_retorno));

 ?>

Would anyone know how to treat that this session was aborted by the client?

Answer 1

Let’s go by step of the problem, your solution to the problem (abort the ajax on the client side) is not the actual solution, the problem is on the server-side.

How do I stop PHP from running?

PHP by default interrupts the request whenever the user gives up the page. The only codition for this not to occur is if you set a ignore_user_abort(true) or if you set the value in ignore_user_abort = 1 in the php.ini.

If the remote client disconnects, the ABORTED state flag is turned on. A remote client Disconnect is usually caused by the user Hitting his STOP button.

The problem is that when you use the mysqli_*, for example, but should also be applicable to your case, this happens to be outside of PHP. Basically PHP no longer has control over it directly. But, after back to the PHP command the process will be killed, understand that when you enter $array_de_retorno process will be killed because user aborted.

But, because if I make another request it awaits previous request?

This is probably the use of SESSION or ISOLAMENTO (and also the LOCKING tables) of the database used. The first situation is extremely likely in your case (and in most cases). There is also the possibility of some defined rate limit, which defines how many requests can be made per client, this can be set in Apache/Nginx (and related).

But, let’s face it, when you do it:

session_start();

Will block writing and recording in session, which is a mere archive, this will cause any other request to be blocked.

One solution is to use the session_write_close() and thus allow another request read and save the data to the session file, because when you call session_write_close() indicates that that process will no longer write anything, but can still read.

See this answer about this same problem.

Answer 2

When you make a request on the front, it is sent to the server, which executes the operation, and when you cancel before receiving the return, you only stop receiving it but the execution continues on the server. You would need to restructure your back code to verify if you could continue execution or not.

Answer 3

Try adding a simple break (http://php.net/manual/en/control-structures.break.php), or exit(http://php.net/manual/en/function.exit.php) in the code php