Allow config of the backoff algorithm for the federation client. (#15754)

Adds three new configuration variables:

* destination_min_retry_interval is identical to before (10mn).
* destination_retry_multiplier is now 2 instead of 5, the maximum value will
  be reached slower.
* destination_max_retry_interval is one day instead of (essentially) infinity.

Capping this will cause destinations to continue to be retried sometimes instead
of being lost forever. The previous value was 2 ^ 62 milliseconds.

1 files changed, 7 insertions, 2 deletions

diff --git a/tests/storage/test_transactions.py b/tests/storage/test_transactions.py
index 2fab84a529..ef06b50dbb 100644
--- a/tests/storage/test_transactions.py
+++ b/tests/storage/test_transactions.py
@@ -17,7 +17,6 @@ from twisted.test.proto_helpers import MemoryReactor
 from synapse.server import HomeServer
 from synapse.storage.databases.main.transactions import DestinationRetryTimings
 from synapse.util import Clock
-from synapse.util.retryutils import MAX_RETRY_INTERVAL
 
 from tests.unittest import HomeserverTestCase
 
@@ -57,8 +56,14 @@ class TransactionStoreTestCase(HomeserverTestCase):
         self.get_success(d)
 
     def test_large_destination_retry(self) -> None:
+        max_retry_interval_ms = (
+            self.hs.config.federation.destination_max_retry_interval_ms
+        )
         d = self.store.set_destination_retry_timings(
-            "example.com", MAX_RETRY_INTERVAL, MAX_RETRY_INTERVAL, MAX_RETRY_INTERVAL
+            "example.com",
+            max_retry_interval_ms,
+            max_retry_interval_ms,
+            max_retry_interval_ms,
         )
         self.get_success(d)