From 5f163008d10a57be0e502488975006f5523b1f6f Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 21 Apr 2015 23:12:59 -0700
Subject: [PATCH] Added LoadBalancer::waitForOne method

* This waits on the generic reader (or a random slave)

Change-Id: I4d4a96806d55b119fa535556e11abd55736e9077
---
 includes/db/LoadBalancer.php | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/includes/db/LoadBalancer.php b/includes/db/LoadBalancer.php
index bc17911f9a..624f46bc3b 100644
--- a/includes/db/LoadBalancer.php
+++ b/includes/db/LoadBalancer.php
@@ -358,6 +358,37 @@ class LoadBalancer {
 		}
 	}
 
+	/**
+	 * Set the master wait position and wait for a "generic" slave to catch up to it
+	 *
+	 * This can be used a faster proxy for waitForAll()
+	 *
+	 * @param DBMasterPos $pos
+	 * @param int $timeout Max seconds to wait; default is mWaitTimeout
+	 * @return bool Success (able to connect and no timeouts reached)
+	 * @since 1.26
+	 */
+	public function waitForOne( $pos, $timeout = null ) {
+		$this->mWaitForPos = $pos;
+
+		$i = $this->mReadIndex;
+		if ( $i <= 0 ) {
+			// Pick a generic slave if there isn't one yet
+			$readLoads = $this->mLoads;
+			unset( $readLoads[$this->getWriterIndex()] ); // slaves only
+			$readLoads = array_filter( $readLoads ); // with non-zero load
+			$i = ArrayUtils::pickRandom( $readLoads );
+		}
+
+		if ( $i > 0 ) {
+			$ok = $this->doWait( $i, true, $timeout );
+		} else {
+			$ok = true; // no applicable loads
+		}
+
+		return $ok;
+	}
+
 	/**
 	 * Set the master wait position and wait for ALL slaves to catch up to it
 	 * @param DBMasterPos $pos
-- 
2.20.1