Remove trailing slashes from outbound federation requests and retry on 400 (#4840)

As per #3622, we remove trailing slashes from outbound federation requests. However, to ensure that we remain backwards compatible with previous versions of Synapse, if we receive a HTTP 400 with `M_UNRECOGNIZED`, then we are likely talking to an older version of Synapse in which case we retry with a trailing slash appended to the request path.

1 files changed, 14 insertions, 7 deletions

diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 8e2be218e2..0cdb31178f 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -51,9 +51,10 @@ class TransportLayerClient(object):
         logger.debug("get_room_state dest=%s, room=%s",
                      destination, room_id)
 
-        path = _create_v1_path("/state/%s/", room_id)
+        path = _create_v1_path("/state/%s", room_id)
         return self.client.get_json(
             destination, path=path, args={"event_id": event_id},
+            try_trailing_slash_on_400=True,
         )
 
     @log_function
@@ -73,9 +74,10 @@ class TransportLayerClient(object):
         logger.debug("get_room_state_ids dest=%s, room=%s",
                      destination, room_id)
 
-        path = _create_v1_path("/state_ids/%s/", room_id)
+        path = _create_v1_path("/state_ids/%s", room_id)
         return self.client.get_json(
             destination, path=path, args={"event_id": event_id},
+            try_trailing_slash_on_400=True,
         )
 
     @log_function
@@ -95,8 +97,11 @@ class TransportLayerClient(object):
         logger.debug("get_pdu dest=%s, event_id=%s",
                      destination, event_id)
 
-        path = _create_v1_path("/event/%s/", event_id)
-        return self.client.get_json(destination, path=path, timeout=timeout)
+        path = _create_v1_path("/event/%s", event_id)
+        return self.client.get_json(
+            destination, path=path, timeout=timeout,
+            try_trailing_slash_on_400=True,
+        )
 
     @log_function
     def backfill(self, destination, room_id, event_tuples, limit):
@@ -121,7 +126,7 @@ class TransportLayerClient(object):
             # TODO: raise?
             return
 
-        path = _create_v1_path("/backfill/%s/", room_id)
+        path = _create_v1_path("/backfill/%s", room_id)
 
         args = {
             "v": event_tuples,
@@ -132,6 +137,7 @@ class TransportLayerClient(object):
             destination,
             path=path,
             args=args,
+            try_trailing_slash_on_400=True,
         )
 
     @defer.inlineCallbacks
@@ -176,6 +182,7 @@ class TransportLayerClient(object):
             json_data_callback=json_data_callback,
             long_retries=True,
             backoff_on_404=True,  # If we get a 404 the other side has gone
+            try_trailing_slash_on_400=True,
         )
 
         defer.returnValue(response)
@@ -959,7 +966,7 @@ def _create_v1_path(path, *args):
 
     Example:
 
-        _create_v1_path("/event/%s/", event_id)
+        _create_v1_path("/event/%s", event_id)
 
     Args:
         path (str): String template for the path
@@ -980,7 +987,7 @@ def _create_v2_path(path, *args):
 
     Example:
 
-        _create_v2_path("/event/%s/", event_id)
+        _create_v2_path("/event/%s", event_id)
 
     Args:
         path (str): String template for the path