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diff --git a/www/wiki/includes/services/SalvageableService.php b/www/wiki/includes/services/SalvageableService.php
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+<?php
+namespace MediaWiki\Services;
+
+/**
+ * Interface for salvageable services.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ *
+ * @since 1.28
+ */
+
+/**
+ * SalvageableService defines an interface for services that are able to salvage state from a
+ * previous instance of the same class. The intent is to allow new service instances to re-use
+ * resources that would be expensive to re-create, such as cached data or network connections.
+ *
+ * @note There is no expectation that services will be destroyed when the process (or web request)
+ * terminates.
+ */
+interface SalvageableService {
+
+	/**
+	 * Re-uses state from $other. $other must not be used after being passed to salvage(),
+	 * and should be considered to be destroyed.
+	 *
+	 * @note Implementations are responsible for determining what parts of $other can be re-used
+	 * safely. In particular, implementations should check that the relevant configuration of
+	 * $other is the same as in $this before re-using resources from $other.
+	 *
+	 * @note Implementations must take care to detach any re-used resources from the original
+	 * service instance. If $other is destroyed later, resources that are now used by the
+	 * new service instance must not be affected.
+	 *
+	 * @note If $other is a DestructibleService, implementations should make sure that $other
+	 * is in destroyed state after salvage finished. This may be done by calling $other->destroy()
+	 * after carefully detaching all relevant resources.
+	 *
+	 * @param SalvageableService $other The object to salvage state from. $other must have the
+	 * exact same type as $this.
+	 */
+	public function salvage( SalvageableService $other );
+
+}