From b0f08062396532875b2872115b2ed43450ec0905 Mon Sep 17 00:00:00 2001
From: Omer Katz <omer.drow@gmail.com>
Date: Tue, 3 Nov 2020 16:35:21 +0200
Subject: [PATCH] When using the MongoDB backend, don't cleanup if
 result_expires is 0 or None.

Fixes #6450.
---
 celery/backends/mongodb.py      | 3 +++
 t/unit/backends/test_mongodb.py | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/celery/backends/mongodb.py b/celery/backends/mongodb.py
index 5ae3ddf822..76eab766b7 100644
--- a/celery/backends/mongodb.py
+++ b/celery/backends/mongodb.py
@@ -248,6 +248,9 @@ def _forget(self, task_id):
 
     def cleanup(self):
         """Delete expired meta-data."""
+        if not self.expires:
+            return
+
         self.collection.delete_many(
             {'date_done': {'$lt': self.app.now() - self.expires_delta}},
         )
diff --git a/t/unit/backends/test_mongodb.py b/t/unit/backends/test_mongodb.py
index fb304b7e36..5a391d86d3 100644
--- a/t/unit/backends/test_mongodb.py
+++ b/t/unit/backends/test_mongodb.py
@@ -485,6 +485,12 @@ def test_cleanup(self, mock_get_database):
         mock_get_database.assert_called_once_with()
         mock_collection.delete_many.assert_called()
 
+        self.backend.collections = mock_collection = Mock()
+        self.backend.expires = None
+
+        self.backend.cleanup()
+        mock_collection.delete_many.assert_not_called()
+
     def test_get_database_authfailure(self):
         x = MongoBackend(app=self.app)
         x._get_connection = Mock()