--- /dev/null
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpKernel\CacheWarmer;
+
+/**
+ * Interface for classes able to warm up the cache.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+interface CacheWarmerInterface extends WarmableInterface
+{
+ /**
+ * Checks whether this warmer is optional or not.
+ *
+ * Optional warmers can be ignored on certain conditions.
+ *
+ * A warmer should return true if the cache can be
+ * generated incrementally and on-demand.
+ *
+ * @return bool true if the warmer is optional, false otherwise
+ */
+ public function isOptional();
+}