Handle SIGINT gracefully

README.md

@@ -97,6 +97,13 @@ command just like version 1.x.
 - `drall exec:drush ...` is now `drall exec drush ...`
 - `drall exec:shell ...` is now `drall exec ...`
 
+#### Interrupting a command
+
+When `drall exec` receives a signal to interrupt (usually `ctrl + c`), Drall
+stops after processing the site that is currently being processed. This
+prevents the current command from terminating abruptly. However, if a second
+interrupt signal is received, then Drall stops immediately.
+
 #### Drush with @@dir
 
 In this method, the `--uri` option is sent to `drush`.

src/Command/ExecCommand.php

@@ -12,6 +12,7 @@
 use Drall\Model\EnvironmentId;
 use Drall\Model\Placeholder;
 use Drall\Model\RawCommand;
+use Drall\Trait\SignalAwareTrait;
 use Symfony\Component\Console\Helper\ProgressBar;
 use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\InputInterface;
@@ -24,6 +25,8 @@
  */
 class ExecCommand extends BaseCommand {
 
+  use SignalAwareTrait;
+
   /**
    * Maximum number of Drall workers.
    *
@@ -163,11 +166,40 @@ protected function execute(InputInterface $input, OutputInterface $output): int
     );
     $exitCode = 0;
 
-    Loop::run(function () use ($values, $command, $placeholder, $output, $progressBar, $workers, &$exitCode) {
+    // Handle interruption signals to stop Drall gracefully.
+    $isStopping = FALSE;
+    $this->registerInterruptionListener(function () use (&$isStopping, $output) {
+      $output->writeln('');
+
+      // If a previous SIGINT was received, then stop immediately.
+      if ($isStopping) {
+        $this->logger->error('Interrupted by user.');
+        exit(1);
+      }
+
+      // Prepare to stop after the current item is processed.
+      $this->logger->warning('Stopping after current item.');
+      $isStopping = TRUE;
+    });
+
+    Loop::run(function () use (
+      $values,
+      $command,
+      $placeholder,
+      $output,
+      $progressBar,
+      $workers,
+      &$exitCode,
+      &$isStopping
+    ) {
       yield ConcurrentIterator\each(
         Iterator\fromIterable($values),
         new LocalSemaphore($workers),
-        function ($value) use ($command, $placeholder, $output, $progressBar, &$exitCode) {
+        function ($value) use ($command, $placeholder, $output, $progressBar, &$exitCode, &$isStopping) {
+          if ($isStopping) {
+            return;
+          }
+
           $sCommand = Placeholder::replace([$placeholder->value => $value], $command);
           $process = new Process("($sCommand) 2>&1", getcwd());
 
@@ -189,9 +221,17 @@ function ($value) use ($command, $placeholder, $output, $progressBar, &$exitCode
       );
     });
 
-    $progressBar->finish();
+    if (!$isStopping) {
+      $progressBar->finish();
+    }
+
     $output->writeln('');
 
+    if ($isStopping) {
+      $this->logger->error('Interrupted by user.');
+      return 1;
+    }
+
     return $exitCode;
   }
 

src/Trait/SignalAwareTrait.php

@@ -26,4 +26,21 @@ protected function registerSignalListener(int $signo, callable $handler): bool {
     return TRUE;
   }
 
+  /**
+   * Register a listener for SIGINT.
+   *
+   * @param callable $handler
+   *   A callable event listener.
+   *
+   * @return bool
+   *   True if the listener was registered.
+   */
+  protected function registerInterruptionListener(callable $handler): bool {
+    if (!defined('SIGINT')) {
+      return FALSE;
+    }
+
+    return self::registerSignalListener(SIGINT, $handler);
+  }
+
 }

src/Trait/SiteDetectorAwareTrait.php

@@ -30,7 +30,7 @@ public function setSiteDetector(SiteDetector $siteDetector) {
   public function siteDetector(): SiteDetector {
     if (!$this->hasSiteDetector()) {
       throw new \BadMethodCallException(
-        'A site detecetor instance must first be assigned'
+        'A site detector instance must first be assigned'
       );
     }