Fixed #34806 -- Made cached_db session backend resilient to cache write errors.

Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>

2 files changed, 23 insertions, 0 deletions

diff --git a/tests/cache/failing_cache.py b/tests/cache/failing_cache.py
new file mode 100644
index 0000000000..e2f0043bb7
--- /dev/null
+++ b/tests/cache/failing_cache.py
@@ -0,0 +1,7 @@
+from django.core.cache.backends.locmem import LocMemCache
+
+
+class CacheClass(LocMemCache):
+
+    def set(self, *args, **kwargs):
+        raise Exception("Faked exception saving to cache")
diff --git a/tests/sessions_tests/tests.py b/tests/sessions_tests/tests.py
index 7e0677d08d..c8c556b4dc 100644
--- a/tests/sessions_tests/tests.py
+++ b/tests/sessions_tests/tests.py
@@ -517,6 +517,22 @@ class CacheDBSessionTests(SessionTestsMixin, TestCase):
         with self.assertRaises(InvalidCacheBackendError):
             self.backend()
 
+    @override_settings(
+        CACHES={"default": {"BACKEND": "cache.failing_cache.CacheClass"}}
+    )
+    def test_cache_set_failure_non_fatal(self):
+        """Failing to write to the cache does not raise errors."""
+        session = self.backend()
+        session["key"] = "val"
+
+        with self.assertLogs("django.contrib.sessions", "ERROR") as cm:
+            session.save()
+
+        # A proper ERROR log message was recorded.
+        log = cm.records[-1]
+        self.assertEqual(log.message, f"Error saving to cache ({session._cache})")
+        self.assertEqual(str(log.exc_info[1]), "Faked exception saving to cache")
+
 
 @override_settings(USE_TZ=True)
 class CacheDBSessionWithTimeZoneTests(CacheDBSessionTests):