Fix a number of "Starting txn from sentinel context" warnings (#5605)

Fixes #5602, #5603

1 files changed, 10 insertions, 3 deletions

diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index 983ce13291..13a3d5208b 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -25,6 +25,7 @@ from twisted.internet import defer
 
 from synapse.api.constants import UserTypes
 from synapse.api.errors import Codes, StoreError, ThreepidValidationError
+from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage import background_updates
 from synapse.storage._base import SQLBaseStore
 from synapse.types import UserID
@@ -619,9 +620,15 @@ class RegistrationStore(
         )
 
         # Create a background job for culling expired 3PID validity tokens
-        hs.get_clock().looping_call(
-            self.cull_expired_threepid_validation_tokens, THIRTY_MINUTES_IN_MS
-        )
+        def start_cull():
+            # run as a background process to make sure that the database transactions
+            # have a logcontext to report to
+            return run_as_background_process(
+                "cull_expired_threepid_validation_tokens",
+                self.cull_expired_threepid_validation_tokens,
+            )
+
+        hs.get_clock().looping_call(start_cull, THIRTY_MINUTES_IN_MS)
 
     @defer.inlineCallbacks
     def _backgroud_update_set_deactivated_flag(self, progress, batch_size):