Add mutex to page tree move function, fix #1518

* Use django-db-mutex module to implement a mutex that allows only
  one page tree move operation at a time.

CHANGELOG.md

@@ -4,6 +4,7 @@ UNRELEASED
 * [ [#2056](https://github.com/digitalfabrik/integreat-cms/issues/2056) ] Change restriction of event duration to 28 days
 * [ [#2032](https://github.com/digitalfabrik/integreat-cms/issues/2032) ] Remove gap between sidebar boxes in location form
 * [ [#1989](https://github.com/digitalfabrik/integreat-cms/issues/1989) ] Improve load time of locations endpoint
+* [ [#1518](https://github.com/digitalfabrik/integreat-cms/issues/1518) ] Prevent database corruption when moving 2 pages at the same time
 
 
 2023.2.0

Pipfile

@@ -29,6 +29,7 @@ twine = "*"
 
 [packages]
 integreat-cms = {editable = true, path = "."}
+django-db-mutex = "*"
 
 [requires]
 python_version = "3.9"

integreat_cms/cms/models/pages/page.py

@@ -11,6 +11,9 @@
 
 from treebeard.ns_tree import NS_NodeQuerySet
 
+from db_mutex import DBMutexError, DBMutexTimeoutError
+from db_mutex.db_mutex import db_mutex
+
 from ...utils.translation_utils import gettext_many_lazy as __
 from ..abstract_content_model import ContentQuerySet
 from ..abstract_tree_node import AbstractTreeNode
@@ -318,9 +321,19 @@ def move(self, target, pos=None):
         :type pos: str
 
         :raises ~treebeard.exceptions.InvalidPosition: If the node is moved to another region
+        :raises ~db_mutex.DBMutexError: If the DB mutex could not be retrieved
+        :raises ~db_mutex.DBMutexTimeoutError: If waiting for the DB mutex timed out
         """
-        super().move(target, pos)
-        invalidate_model(PageTranslation)
+        try:
+            with db_mutex(f"tree-page-{self.region}"):
+                super().move(target, pos)
+                invalidate_model(PageTranslation)
+        except DBMutexError as e:
+            logger.error("Could not retrieve database mutex to save %s", self)
+            raise DBMutexError from e
+        except DBMutexTimeoutError as e:
+            logger.error("Retrieving database mutex timed out while saving %s", self)
+            raise DBMutexTimeoutError from e
 
     def archive(self):
         """

integreat_cms/core/settings.py

@@ -247,6 +247,7 @@
     "django.contrib.staticfiles",
     # Installed third-party-apps
     "corsheaders",
+    "db_mutex",
     "linkcheck",
     "polymorphic",
     "rules.apps.AutodiscoverRulesConfig",