Merge pull request #6842 from nupplaphil/issue/6788-multiple_admin_notify

Avoid double update runs

src/Core/Update.php

@@ -24,19 +24,15 @@ class Update
 			return;
 		}
 
-		$build = Config::get('system', 'build');
-
-		if (empty($build)) {
-			Config::set('system', 'build', DB_UPDATE_VERSION - 1);
-			$build = DB_UPDATE_VERSION - 1;
-		}
+		$build = self::getBuild();
+		$current = intval(DB_UPDATE_VERSION);
 
 		// We don't support upgrading from very old versions anymore
 		if ($build < NEW_UPDATE_ROUTINE_VERSION) {
 			die('You try to update from a version prior to database version 1170. The direct upgrade path is not supported. Please update to version 3.5.4 before updating to this version.');
 		}
 
-		if ($build < DB_UPDATE_VERSION) {
+		if ($build < $current ) {
 			if ($via_worker) {
 				// Calling the database update directly via the worker enables us to perform database changes to the workerqueue table itself.
 				// This is a fallback, since normally the database update will be performed by a worker job.
@@ -68,26 +64,26 @@ class Update
 			Lock::release('dbupdate', true);
 		}
 
-		$build = Config::get('system', 'build');
+		$current = intval(DB_UPDATE_VERSION);
+		$stored = self::getBuild();
 
-		if (empty($build) || ($build > DB_UPDATE_VERSION)) {
-			$build = DB_UPDATE_VERSION - 1;
-			Config::set('system', 'build', $build);
-		}
-
-		if ($build != DB_UPDATE_VERSION || $force) {
+		if ($stored < $current || $force) {
 			require_once 'update.php';
 
-			$stored = intval($build);
-			$current = intval(DB_UPDATE_VERSION);
-			if ($stored < $current || $force) {
 			Config::load('database');
 
 			Logger::log('Update from \'' . $stored . '\'  to \'' . $current . '\' - starting', Logger::DEBUG);
 
 			// Compare the current structure with the defined structure
 			// If the Lock is acquired, never release it automatically to avoid double updates
-				if (Lock::acquire('dbupdate', 120, Cache::INFINITE)) {
+			if (Lock::acquire('dbupdate', 0, Cache::INFINITE)) {
+
+				// recheck again in case we accidentally spawned multiple updates
+				$stored = self::getBuild();
+				if ($stored >= $current) {
+					Lock::release('dbupdate');
+					return '';
+				}
 
 				// run the pre_update_nnnn functions in update.php
 				for ($x = $stored + 1; $x <= $current; $x++) {
@@ -131,7 +127,6 @@ class Update
 				Lock::release('dbupdate');
 			}
 		}
-		}
 
 		return '';
 	}
@@ -293,4 +288,21 @@ class Update
 		//try the logger
 		Logger::log("Database structure update successful.", Logger::TRACE);
 	}
+
+	/**
+	 * Returns the current build number of the instance
+	 *
+	 * @return int the build number
+	 */
+	private static function getBuild()
+	{
+		$build = Config::get('system', 'build');
+
+		if (empty($build) || ($build > DB_UPDATE_VERSION)) {
+			$build = DB_UPDATE_VERSION - 1;
+			Config::set('system', 'build', $build);
+		}
+
+		return (is_int($build) ? intval($build) : DB_UPDATE_VERSION - 1);
+	}
 }