Properly update retry_last_ts when hitting the maximum retry interval (#16156)

* Properly update retry_last_ts when hitting the maximum retry interval

This was broken in 1.87 when the maximum retry interval got changed from
almost infinite to a week (and made configurable).

fixes #16101

Signed-off-by: Nicolas Werner <nicolas.werner@hotmail.de>

* Add changelog

* Change fix + add test

* Add comment

---------

Signed-off-by: Nicolas Werner <nicolas.werner@hotmail.de>
Co-authored-by: Mathieu Velten <mathieuv@matrix.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/tests/util/test_retryutils.py b/tests/util/test_retryutils.py

index 1277e1a865..4bcd17a6fc 100644
--- a/tests/util/test_retryutils.py
+++ b/tests/util/test_retryutils.py
@@ -108,3 +108,54 @@ class RetryLimiterTestCase(HomeserverTestCase):
 
         new_timings = self.get_success(store.get_destination_retry_timings("test_dest"))
         self.assertIsNone(new_timings)
+
+    def test_max_retry_interval(self) -> None:
+        """Test that `destination_max_retry_interval` setting works as expected"""
+        store = self.hs.get_datastores().main
+
+        destination_max_retry_interval_ms = (
+            self.hs.config.federation.destination_max_retry_interval_ms
+        )
+
+        self.get_success(get_retry_limiter("test_dest", self.clock, store))
+        self.pump(1)
+
+        failure_ts = self.clock.time_msec()
+
+        # Simulate reaching destination_max_retry_interval
+        self.get_success(
+            store.set_destination_retry_timings(
+                "test_dest",
+                failure_ts=failure_ts,
+                retry_last_ts=failure_ts,
+                retry_interval=destination_max_retry_interval_ms,
+            )
+        )
+
+        # Check it fails
+        self.get_failure(
+            get_retry_limiter("test_dest", self.clock, store), NotRetryingDestination
+        )
+
+        # Get past retry_interval and we can try again, and still throw an error to continue the backoff
+        self.reactor.advance(destination_max_retry_interval_ms / 1000 + 1)
+        limiter = self.get_success(get_retry_limiter("test_dest", self.clock, store))
+        self.pump(1)
+        try:
+            with limiter:
+                self.pump(1)
+                raise AssertionError("argh")
+        except AssertionError:
+            pass
+
+        self.pump()
+
+        # retry_interval does not increase and stays at destination_max_retry_interval_ms
+        new_timings = self.get_success(store.get_destination_retry_timings("test_dest"))
+        assert new_timings is not None
+        self.assertEqual(new_timings.retry_interval, destination_max_retry_interval_ms)
+
+        # Check it fails
+        self.get_failure(
+            get_retry_limiter("test_dest", self.clock, store), NotRetryingDestination
+        )