From: Aaron Schulz <aschulz@wikimedia.org>
Date: Mon, 2 Apr 2018 19:56:11 +0000 (-0700)
Subject: rdbms: avoid incorrect warnings in getLagFromPtHeartbeat()
X-Git-Tag: 1.31.0-rc.0~230
X-Git-Url: https://git.cyclocoop.org/admin/%7B%7Blocalurl:Special:UserLogin%7D%7D?a=commitdiff_plain;h=c3f084d44bab25a16fa110023859db81bce39100;p=lhc%2Fweb%2Fwiklou.git

rdbms: avoid incorrect warnings in getLagFromPtHeartbeat()

Change-Id: I4c0d42be0ee0c518d7bacdae0f76feb53007861e
---

diff --git a/includes/libs/rdbms/database/DatabaseMysqlBase.php b/includes/libs/rdbms/database/DatabaseMysqlBase.php
index e6acaa9fa2..0a63bdc6f1 100644
--- a/includes/libs/rdbms/database/DatabaseMysqlBase.php
+++ b/includes/libs/rdbms/database/DatabaseMysqlBase.php
@@ -73,6 +73,9 @@ abstract class DatabaseMysqlBase extends Database {
 	// Cache getServerId() for 24 hours
 	const SERVER_ID_CACHE_TTL = 86400;
 
+	/** @var float Warn if lag estimates are made for transactions older than this many seconds */
+	const LAG_STALE_WARN_THRESHOLD = 0.100;
+
 	/**
 	 * Additional $params include:
 	 *   - lagDetectionMethod : set to one of (Seconds_Behind_Master,pt-heartbeat).
@@ -763,7 +766,10 @@ abstract class DatabaseMysqlBase extends Database {
 	protected function getLagFromPtHeartbeat() {
 		$options = $this->lagDetectionOptions;
 
-		if ( $this->trxLevel ) {
+		$staleness = $this->trxLevel
+			? microtime( true ) - $this->trxTimestamp()
+			: 0;
+		if ( $staleness > self::LAG_STALE_WARN_THRESHOLD ) {
 			// Avoid returning higher and higher lag value due to snapshot age
 			// given that the isolation level will typically be REPEATABLE-READ
 			$this->queryLogger->warning(