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diff --git a/www/wiki/includes/libs/rdbms/loadmonitor/ILoadMonitor.php b/www/wiki/includes/libs/rdbms/loadmonitor/ILoadMonitor.php
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+<?php
+/**
+ * Database load monitoring interface
+ *
+ * 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
+ * @ingroup Database
+ */
+
+namespace Wikimedia\Rdbms;
+
+use Psr\Log\LoggerAwareInterface;
+use BagOStuff;
+use WANObjectCache;
+
+/**
+ * An interface for database load monitoring
+ *
+ * @ingroup Database
+ */
+interface ILoadMonitor extends LoggerAwareInterface {
+	/**
+	 * Construct a new LoadMonitor with a given LoadBalancer parent
+	 *
+	 * @param ILoadBalancer $lb LoadBalancer this instance serves
+	 * @param BagOStuff $sCache Local server memory cache
+	 * @param WANObjectCache $wCache Local cluster memory cache
+	 * @param array $options Options map
+	 */
+	public function __construct(
+		ILoadBalancer $lb, BagOStuff $sCache, WANObjectCache $wCache, array $options = []
+	);
+
+	/**
+	 * Perform load ratio adjustment before deciding which server to use
+	 *
+	 * @param int[] &$weightByServer Map of (server index => float weight)
+	 * @param string|bool $domain
+	 */
+	public function scaleLoads( array &$weightByServer, $domain );
+
+	/**
+	 * Get an estimate of replication lag (in seconds) for each server
+	 *
+	 * Values may be "false" if replication is too broken to estimate
+	 *
+	 * @param int[] $serverIndexes
+	 * @param string $domain
+	 * @return array Map of (server index => float|int|bool)
+	 */
+	public function getLagTimes( array $serverIndexes, $domain );
+}