MDL-24962 backup - clean plan/settings circular refs on restore

backup/controller/restore_controller.class.php

@@ -135,6 +135,23 @@ class restore_controller extends backup implements loggable {
         }
     }
 
+    /**
+     * Clean structures used by the restore_controller
+     *
+     * This method clean various structures used by the restore_controller,
+     * destroying them in an ordered way, so their memory will be gc properly
+     * by PHP (mainly circular references).
+     *
+     * Note that, while it's not mandatory to execute this method, it's highly
+     * recommended to do so, specially in scripts performing multiple operations
+     * (like the automated backups) or the system will run out of memory after
+     * a few dozens of backups)
+     */
+    public function destroy() {
+        // Only need to destroy circulars under the plan. Delegate to it.
+        $this->plan->destroy();
+    }
+
     public function finish_ui() {
         if ($this->status != backup::STATUS_SETTING_UI) {
             throw new restore_controller_exception('cannot_finish_ui_if_not_setting_ui');
@@ -157,7 +174,9 @@ class restore_controller extends backup implements loggable {
         // containing all the steps will be sent to DB. 100% (monster) useless.
         if ($status == backup::STATUS_AWAITING || $status == backup::STATUS_NEED_PRECHECK) {
             $this->save_controller();
-            $this->logger = self::load_controller($this->restoreid)->logger; // wakeup loggers
+            $tbc = self::load_controller($this->restoreid);
+            $this->logger = $tbc->logger; // wakeup loggers
+            $tbc->destroy(); // Clean temp controller structures
         }
     }