diff --git a/changelog.d/13890.misc b/changelog.d/13890.misc
new file mode 100644
index 0000000000..bf76cf7be7
--- /dev/null
+++ b/changelog.d/13890.misc
@@ -0,0 +1 @@
+Improve backfill robustness by trying more servers when we get a `4xx` error back.
\ No newline at end of file
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 500c1c16d0..b866258298 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -417,6 +417,15 @@ class FederationHandler:
async def try_backfill(domains: Collection[str]) -> bool:
# TODO: Should we try multiple of these at a time?
+
+ # Number of contacted remote homeservers that have denied our backfill
+ # request with a 4xx code.
+ denied_count = 0
+
+ # Maximum number of contacted remote homeservers that can deny our
+ # backfill request with 4xx codes before we give up.
+ max_denied_count = 5
+
for dom in domains:
# We don't want to ask our own server for information we don't have
if dom == self.server_name:
@@ -435,13 +444,33 @@ class FederationHandler:
continue
except HttpResponseException as e:
if 400 <= e.code < 500:
- raise e.to_synapse_error()
+ logger.warning(
+ "Backfill denied from %s because %s [%d/%d]",
+ dom,
+ e,
+ denied_count,
+ max_denied_count,
+ )
+ denied_count += 1
+ if denied_count >= max_denied_count:
+ return False
+ continue
logger.info("Failed to backfill from %s because %s", dom, e)
continue
except CodeMessageException as e:
if 400 <= e.code < 500:
- raise
+ logger.warning(
+ "Backfill denied from %s because %s [%d/%d]",
+ dom,
+ e,
+ denied_count,
+ max_denied_count,
+ )
+ denied_count += 1
+ if denied_count >= max_denied_count:
+ return False
+ continue
logger.info("Failed to backfill from %s because %s", dom, e)
continue
|
