Fix task_deindex_instance crash when object deleted before task runs

mayan/apps/dynamic_search/tasks.py

@@ -28,7 +28,15 @@ def task_deindex_instance(self, app_label, model_name, object_id):
     logger.info('Executing')
 
     Model = apps.get_model(app_label=app_label, model_name=model_name)
-    instance = Model._meta.default_manager.get(pk=object_id)
+
+    try:
+        instance = Model._meta.default_manager.get(pk=object_id)
+    except Model.DoesNotExist:
+        logger.warning(
+            'Object %s with pk=%s no longer exists; '
+            'skipping de-indexing.', Model, object_id
+        )
+        return
 
     try:
         SearchBackend.get_instance().deindex_instance(instance=instance)

mayan/apps/dynamic_search/tests/test_tasks.py

@@ -3,6 +3,7 @@
 from mayan.apps.testing.tests.base import BaseTestCase
 
 from ..classes import SearchBackend, SearchModel
+from ..tasks import task_deindex_instance
 
 from .mixins import SearchTaskTestMixin, SearchTestMixin
 
@@ -60,3 +61,29 @@ def test_task_reindex_backend(self):
             search_terms=self._test_objects[0].test_field
         )
         self.assertTrue(self._test_objects[0] in queryset)
+
+    def test_task_deindex_instance_object_already_deleted(self):
+        """
+        task_deindex_instance must not crash when the object no longer exists.
+
+        This is a race condition that occurs when a document is deleted (e.g.
+        from the trash) and the de-index task executes after the DELETE has
+        already committed.  Before this fix the task raised DoesNotExist and
+        logged a CRITICAL traceback; now it logs a warning and returns cleanly.
+        Regression test for GitLab issue #1185.
+        """
+        obj = self._test_objects[0]
+        app_label = obj._meta.app_label
+        model_name = obj._meta.model_name
+        pk = obj.pk
+
+        obj.delete()
+
+        # Must complete without raising any exception.
+        task_deindex_instance.apply_async(
+            kwargs={
+                'app_label': app_label,
+                'model_name': model_name,
+                'object_id': pk,
+            }
+        ).get()