Remove trailing slashes from outbound federation requests

changelog.d/4840.feature

@@ -0,0 +1 @@
+Remove trailing slashes from certain outbound federation requests. Retry if receiving a 404. Context: #3622.

synapse/federation/transport/client.py

@@ -51,9 +51,10 @@ def get_room_state(self, destination, room_id, event_id):
         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_404=True,
         )
 
     @log_function
@@ -73,9 +74,10 @@ def get_room_state_ids(self, destination, room_id, event_id):
         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_404=True,
         )
 
     @log_function
@@ -95,8 +97,11 @@ def get_event(self, destination, event_id, timeout=None):
         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_404=True,
+        )
 
     @log_function
     def backfill(self, destination, room_id, event_tuples, limit):
@@ -121,7 +126,7 @@ def backfill(self, destination, room_id, event_tuples, limit):
             # 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 @@ def backfill(self, destination, room_id, event_tuples, limit):
             destination,
             path=path,
             args=args,
+            try_trailing_slash_on_404=True,
         )
 
     @defer.inlineCallbacks
@@ -176,6 +182,7 @@ def send_transaction(self, transaction, json_data_callback=None):
             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_404=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

synapse/http/matrixfederationclient.py

@@ -196,7 +196,8 @@ def _send_request(
         timeout=None,
         long_retries=False,
         ignore_backoff=False,
-        backoff_on_404=False
+        backoff_on_404=False,
+        try_trailing_slash_on_404=False,
     ):
         """
         Sends a request to the given server.
@@ -212,6 +213,11 @@ def _send_request(
 
             backoff_on_404 (bool): Back off if we get a 404
 
+            try_trailing_slash_on_404 (bool): True if on a 404 response we
+                should try appending a trailing slash to the end of the
+                request. This will be attempted before backing off if backing
+                off has been enabled.
+
         Returns:
             Deferred[twisted.web.client.Response]: resolves with the HTTP
             response object on success.
@@ -473,7 +479,8 @@ def put_json(self, destination, path, args={}, data={},
                  json_data_callback=None,
                  long_retries=False, timeout=None,
                  ignore_backoff=False,
-                 backoff_on_404=False):
+                 backoff_on_404=False,
+                 try_trailing_slash_on_404=False):
         """ Sends the specifed json data using PUT
 
         Args:
@@ -493,7 +500,11 @@ def put_json(self, destination, path, args={}, data={},
                 and try the request anyway.
             backoff_on_404 (bool): True if we should count a 404 response as
                 a failure of the server (and should therefore back off future
-                requests)
+                requests).
+            try_trailing_slash_on_404 (bool): True if on a 404 response we
+                should try appending a trailing slash to the end of the
+                request. This will be attempted before backing off if backing
+                off has been enabled.
 
         Returns:
             Deferred[dict|list]: Succeeds when we get a 2xx HTTP response. The
@@ -509,7 +520,6 @@ def put_json(self, destination, path, args={}, data={},
             RequestSendFailed: If there were problems connecting to the
                 remote, due to e.g. DNS failures, connection timeouts etc.
         """
-
         request = MatrixFederationRequest(
             method="PUT",
             destination=destination,
@@ -519,13 +529,26 @@ def put_json(self, destination, path, args={}, data={},
             json=data,
         )
 
-        response = yield self._send_request(
-            request,
-            long_retries=long_retries,
-            timeout=timeout,
-            ignore_backoff=ignore_backoff,
-            backoff_on_404=backoff_on_404,
-        )
+        send_request_args = {
+            "request": request,
+            "long_retries": long_retries,
+            "timeout": timeout,
+            "ignore_backoff": ignore_backoff,
+            # Do not backoff on the initial request if we're trying with trailing slashes
+            # Otherwise we may end up waiting to contact a server that is actually up
+            "backoff_on_404": False if try_trailing_slash_on_404 else backoff_on_404,
+        }
+
+        response = yield self._send_request(**send_request_args)
+
+        # If enabled, retry with a trailing slash if we received a 404
+        if try_trailing_slash_on_404 and response.code == 404:
+            args["path"] += "/"
+
+            # Re-enable backoff if enabled
+            send_request_args["backoff_on_404"] = backoff_on_404
+
+            response = yield self.get_json(**send_request_args)
 
         body = yield _handle_json_response(
             self.hs.get_reactor(), self.default_timeout, request, response,
@@ -592,7 +615,8 @@ def post_json(self, destination, path, data={}, long_retries=False,
 
     @defer.inlineCallbacks
     def get_json(self, destination, path, args=None, retry_on_dns_fail=True,
-                 timeout=None, ignore_backoff=False):
+                 timeout=None, ignore_backoff=False,
+                 try_trailing_slash_on_404=False):
         """ GETs some json from the given host homeserver and path
 
         Args:
@@ -606,6 +630,9 @@ def get_json(self, destination, path, args=None, retry_on_dns_fail=True,
                 be retried.
             ignore_backoff (bool): true to ignore the historical backoff data
                 and try the request anyway.
+            try_trailing_slash_on_404 (bool): True if on a 404 response we
+                should try appending a trailing slash to the end of the
+                request.
         Returns:
             Deferred[dict|list]: Succeeds when we get a 2xx HTTP response. The
             result will be the decoded JSON body.
@@ -631,12 +658,19 @@ def get_json(self, destination, path, args=None, retry_on_dns_fail=True,
             query=args,
         )
 
-        response = yield self._send_request(
-            request,
-            retry_on_dns_fail=retry_on_dns_fail,
-            timeout=timeout,
-            ignore_backoff=ignore_backoff,
-        )
+        send_request_args = {
+            "request": request,
+            "retry_on_dns_fail": retry_on_dns_fail,
+            "timeout": timeout,
+            "ignore_backoff": ignore_backoff,
+        }
+
+        response = yield self._send_request(**send_request_args)
+
+        # If enabled, retry with a trailing slash if we received a 404
+        if try_trailing_slash_on_404 and response.code == 404:
+            args["path"] += "/"
+            response = yield self._send_request(**send_request_args)
 
         body = yield _handle_json_response(
             self.hs.get_reactor(), self.default_timeout, request, response,

tests/handlers/test_typing.py

@@ -192,6 +192,7 @@ def test_started_typing_remote_send(self):
             json_data_callback=ANY,
             long_retries=True,
             backoff_on_404=True,
+            try_trailing_slash_on_404=True,
         )
 
     def test_started_typing_remote_recv(self):
@@ -269,6 +270,7 @@ def test_stopped_typing(self):
             json_data_callback=ANY,
             long_retries=True,
             backoff_on_404=True,
+            try_trailing_slash_on_404=True,
         )
 
         self.assertEquals(self.event_source.get_current_key(), 1)