From: Aaron Schulz <aschulz@wikimedia.org>
Date: Thu, 18 Oct 2018 18:42:27 +0000 (-0700)
Subject: objectcache: avoid using heavily time-drifted microtime() values in WAN cache
X-Git-Tag: 1.34.0-rc.0~3723^2
X-Git-Url: https://git.cyclocoop.org/%7B%24admin_url%7Dmembres/cotisations/Dunav?a=commitdiff_plain;h=d2c2bf6553c07ea6dd089efd1c7ba62826eea009;p=lhc%2Fweb%2Fwiklou.git

objectcache: avoid using heavily time-drifted microtime() values in WAN cache

Change-Id: Ifcb9e4b4a1d5adfdaaa6ea505e34956516b871de
---

diff --git a/includes/libs/objectcache/WANObjectCache.php b/includes/libs/objectcache/WANObjectCache.php
index 3af820b883..e7586cfe02 100644
--- a/includes/libs/objectcache/WANObjectCache.php
+++ b/includes/libs/objectcache/WANObjectCache.php
@@ -2225,7 +2225,17 @@ class WANObjectCache implements IExpiringStore, LoggerAwareInterface {
 	 * @codeCoverageIgnore
 	 */
 	protected function getCurrentTime() {
-		return $this->wallClockOverride ?: microtime( true );
+		if ( $this->wallClockOverride ) {
+			return $this->wallClockOverride;
+		}
+
+		$clockTime = (float)time(); // call this first
+		// microtime() uses an initial gettimeofday() call added to usage clocks.
+		// This can severely drift from time() and the microtime() value of other threads
+		// due to undercounting of the amount of time elapsed. Instead of seeing the current
+		// time as being in the past, use the value of time(). This avoids setting cache values
+		// that will immediately be seen as expired and possibly cause stampedes.
+		return max( microtime( true ), $clockTime );
 	}
 
 	/**