Prevent locking after process submission - PHP - php

Question

I have a page where a user can select from multiple processes to run. The short version of what I want to accomplish is: Select a process, click Execute, and go about the rest of your work on the site while it runs in the background.
The problem I face is, after the process is submitted, the users can not take any further actions on the site. They can not navigate away from the page, log out, or anything else.
The code for the page is this:
<h1>Execute Processes</h1>
<div class='box'>
<select id='processes' style='width:300px;'>
<option value=''>Processes</option>
<option value='test'>Test Process</option>
</select><br />
<input type="submit" value="Execute" id='execute'/>
</div>
<script>
$("#execute").click(function() {
var process = $("#processes").val();
if(process != "") {
$.ajax({
url: '_processes/' + process + '.php',
type: "POST",
data: {}
});
message_popup("Process submitted");
} else {
alert("Please select a process");
}
});
</script>
For this example, we only have one process. "test.php". The code for "test.php" is this:
<?php
require_once("../_include/constants.php");
require_once("../_include/connection.php");
require_once("../_include/_functions/functions_common.php");
require_once("../_include/_functions/functions_form.php");
require_once("../_include/_functions/functions_browser.php");
require_once("../_include/_functions/functions_legacy.php");
require_once("../_include/_functions/functions_data.php");
$p_name = "Sample Process";
$unix_pid = getmypid();
$p_started_by = mysqli_prep($_SESSION['username']);
execute_query("INSERT INTO site_process_monitor (process_id,process_name,start_time,status,started_by) VALUES ({$unix_pid},'{$p_name}',NOW(),'Started','{$p_started_by}')");//PROCESS START
$p_id = mysqli_insert_id($connection);
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
sleep(60);
//CLOSING STATS////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
execute_query("UPDATE site_process_monitor SET end_time = NOW(), status = 'Completed' WHERE id = {$p_id}");//PROCESS COMPLETE
?>
Very basic. Output some opening stats to the process monitor table on my database, wait 60 seconds, output some closing stats.
Is there a way to start this process so that my user can continue to browse the site and perform other tasks (or submit other processes)?

Answer 1

If you're using default file-based sessions in PHP, note that PHP will keep the session file locked while any particular script instance is using it. This will prevent a user from using any other session-enabled part of your site, as each of their requests will now be waiting for the session lock to be relinquished.
For long-running scripts, you'll need to explicitly release the session lock:
session_write_close();
the_long_running_job();
session_start();
$_SESSION will still be available after you "close" it. But any changes made to $_SESSION will be lost since PHP won't "re-close" it when the script exits.

Answer 2

I think you need to use a Web Worker:
https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/basic_usage
A Web Worker spawns a new browser thread which ensures that user interactions on the page are not hindered.
However, because Web Workers don't have direct DOM access you won't be able to use JQuery to do your ajax request. You will have to write your own XMLHttpRequest.
http://techslides.com/html5-web-workers-for-ajax-requests
I hope this helps.

Answer 3

Javascript will never block the UI thread of a web page. (Sorry, but the "web worker" answer below is naive). If your UI (in javascript) becomes unresponsive, you probably have an infinite loop. Check your network panel on your browser and see if hundreds of POSTs are being done. Try moving the POST action outside of the $("#execute").click(function(). Perhaps you have an id="execute" elsewhere on the page, triggering multiple recursive click()'s.