Implement graceful shutdown for background task runner #2451

common/framework/Queue.php

@@ -11,6 +11,7 @@ class Queue
 	 * Static properties.
 	 */
 	protected static $_drivers = [];
+	protected static $_signal = 0;
 
 	/**
 	 * Priority constants.
@@ -346,6 +347,11 @@ class Queue
 			foreach ($tasks as $task)
 			{
 				self::_executeTask($task);
+
+				if (self::signalReceived())
+				{
+					return;
+				}
 			}
 		}
 		if ($index === 1 || $count < 2)
@@ -356,6 +362,11 @@ class Queue
 			{
 				$db_driver->updateLastRunTimestamp($task);
 				self::_executeTask($task);
+
+				if (self::signalReceived())
+				{
+					return;
+				}
 			}
 		}
 
@@ -368,6 +379,11 @@ class Queue
 			if ($task)
 			{
 				self::_executeTask($task);
+
+				if (self::signalReceived())
+				{
+					return;
+				}
 			}
 
 			// If the timeout is imminent, break the loop.
@@ -383,6 +399,12 @@ class Queue
 			{
 				usleep(intval((1 - $loop_elapsed_time) * 1000000));
 			}
+
+			// Check for a signal again after the sleep.
+			if (self::signalReceived())
+			{
+				break;
+			}
 		}
 	}
 
@@ -488,4 +510,26 @@ class Queue
 			]));
 		}
 	}
+
+	/**
+	 * Signal handler.
+	 *
+	 * @param int $signal
+	 * @param mixed $siginfo
+	 * @return void
+	 */
+	public static function signalHandler(int $signal, $siginfo): void
+	{
+		self::$_signal = $signal;
+	}
+
+	/**
+	 * Has a signal been received?
+	 *
+	 * @return int
+	 */
+	public static function signalReceived(): int
+	{
+		return self::$_signal;
+	}
 }

common/scripts/cron.php

@@ -52,6 +52,19 @@ if (PHP_SAPI !== 'cli')
 	}
 }
 
+// Set up a signal handler.
+if (PHP_SAPI === 'cli' && function_exists('pcntl_signal'))
+{
+	if (function_exists('pcntl_async_signals'))
+	{
+		pcntl_async_signals(true);
+	}
+	foreach ([SIGINT, SIGHUP, SIGTERM, SIGQUIT, SIGUSR1, SIGUSR2] as $signal)
+	{
+		pcntl_signal($signal, [Rhymix\Framework\Queue::class, 'signalHandler']);
+	}
+}
+
 // Create multiple processes if configured.
 if (PHP_SAPI === 'cli' && $process_count > 1 && function_exists('pcntl_fork') && function_exists('pcntl_waitpid'))
 {
@@ -84,7 +97,7 @@ if (PHP_SAPI === 'cli' && $process_count > 1 && function_exists('pcntl_fork') &&
 	}
 
 	// The parent process waits for its children to finish.
-	while (count($pids))
+	while (count($pids) && !Rhymix\Framework\Queue::signalReceived())
 	{
 		$pid = pcntl_waitpid(-1, $status, \WNOHANG);
 		if ($pid)