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-rw-r--r--engine/lib/admin.php1
-rw-r--r--engine/lib/upgrade.php55
2 files changed, 56 insertions, 0 deletions
diff --git a/engine/lib/admin.php b/engine/lib/admin.php
index 3f23f079c..cb9524f11 100644
--- a/engine/lib/admin.php
+++ b/engine/lib/admin.php
@@ -233,6 +233,7 @@ function admin_init() {
elgg_register_action('admin/site/update_basic', '', 'admin');
elgg_register_action('admin/site/update_advanced', '', 'admin');
elgg_register_action('admin/site/flush_cache', '', 'admin');
+ elgg_register_action('admin/site/unlock_upgrade', '', 'admin');
elgg_register_action('admin/menu/save', '', 'admin');
diff --git a/engine/lib/upgrade.php b/engine/lib/upgrade.php
index f0874a483..f4f4b16f5 100644
--- a/engine/lib/upgrade.php
+++ b/engine/lib/upgrade.php
@@ -311,3 +311,58 @@ function elgg_upgrade_bootstrap_17_to_18() {
return elgg_set_processed_upgrades($processed_upgrades);
}
+
+/**
+ * Creates a table {prefix}upgrade_lock that is used as a mutex for upgrades.
+ *
+ * @see _elgg_upgrade_lock()
+ *
+ * @return bool
+ * @access private
+ */
+function _elgg_upgrade_lock() {
+ global $CONFIG;
+
+ if (!_elgg_upgrade_is_locked()) {
+ // lock it
+ insert_data("create table {$CONFIG->dbprefix}upgrade_lock (id INT)");
+ elgg_log('Locked for upgrade.', 'NOTICE');
+ return true;
+ }
+
+ elgg_log('Cannot lock for upgrade: already locked.', 'WARNING');
+ return false;
+}
+
+/**
+ * Unlocks upgrade.
+ *
+ * @see _elgg_upgrade_lock()
+ *
+ * @access private
+ */
+function _elgg_upgrade_unlock() {
+ global $CONFIG;
+ delete_data("drop table {$CONFIG->dbprefix}upgrade_lock");
+ elgg_log('Upgrade unlocked.', 'NOTICE');
+}
+
+/**
+ * Checks if upgrade is locked
+ *
+ * @return bool
+ * @access private
+ */
+function _elgg_upgrade_is_locked() {
+ global $CONFIG, $DB_QUERY_CACHE;
+
+ $is_locked = count(get_data("show tables like '{$CONFIG->dbprefix}upgrade_lock'"));
+
+ // Invalidate query cache
+ if ($DB_QUERY_CACHE) {
+ $DB_QUERY_CACHE->clear();
+ elgg_log("Query cache invalidated", 'NOTICE');
+ }
+
+ return $is_locked;
+}