Implement multiprocessing, and try to make webcron more resilient

common/framework/Queue.php

@@ -178,9 +178,6 @@ class Queue
 	 */
 	public static function process(int $timeout): void
 	{
-		// Increase the time limit. This may or may not work.
-		set_time_limit(min(60, $timeout));
-
 		// This part will run in a loop until timeout.
 		$process_start_time = microtime(true);
 		while (true)

common/scripts/cron.php

@@ -22,6 +22,7 @@ else
 	$key = (string)Context::get('key');
 	if (!Rhymix\Framework\Queue::checkKey($key))
 	{
+		Context::setCacheControl(0);
 		header('HTTP/1.1 403 Forbidden');
 		echo "Invalid key\n";
 		Context::close();
@@ -29,6 +30,60 @@ else
 	}
 }
 
-// The rest of the work will be done by the Queue class.
+// Get queue configuration set by the administrator.
 $timeout = (config('queue.interval') ?? 1) * 60;
-Rhymix\Framework\Queue::process($timeout);
+$process_count = config('queue.process_count') ?? 1;
+
+// If called over the network, try to increase the timeout.
+if (PHP_SAPI !== 'cli')
+{
+	ignore_user_abort(true);
+	set_time_limit(max(60, $timeout));
+}
+
+// Create multiple processes if configured.
+if (PHP_SAPI === 'cli' && $process_count > 1 && function_exists('pcntl_fork') && function_exists('pcntl_waitpid'))
+{
+	// This array will keep a dictionary of subprocesses.
+	$pids = [];
+
+	// The database connection must be closed before forking.
+	Rhymix\Framework\DB::getInstance()->disconnect();
+	Rhymix\Framework\Debug::disable();
+
+	// Create the required number of subprocesses.
+	for ($i = 0; $i < $process_count; $i++)
+	{
+		$pid = pcntl_fork();
+		if ($pid > 0)
+		{
+			$pids[$pid] = true;
+			usleep(200000);
+		}
+		elseif ($pid == 0)
+		{
+			Rhymix\Framework\Queue::process($timeout);
+			exit;
+		}
+		else
+		{
+			error_log('RxQueue: could not fork!');
+			exit;
+		}
+	}
+
+	// The parent process waits for its children to finish.
+	while (count($pids))
+	{
+		$pid = pcntl_waitpid(-1, $status, \WNOHANG);
+		if ($pid)
+		{
+			unset($pids[$pid]);
+		}
+		usleep(200000);
+	}
+}
+else
+{
+	Rhymix\Framework\Queue::process($timeout);
+}