Notary server: make requests to origins in parallel

... else we're guaranteed to time out.

synapse/crypto/keyring.py

@@ -751,7 +751,15 @@ class ServerKeyFetcher(BaseV2KeyFetcher):
         self.client = hs.get_http_client()
 
     def get_keys(self, keys_to_fetch):
-        """see KeyFetcher.get_keys"""
+        """
+        Args:
+            keys_to_fetch (dict[str, iterable[str]]):
+                the keys to be fetched. server_name -> key_ids
+
+        Returns:
+            Deferred[dict[str, dict[str, synapse.storage.keys.FetchKeyResult|None]]]:
+                map from server_name -> key_id -> FetchKeyResult
+        """
 
         results = {}
 

synapse/rest/key/v2/remote_key_resource.py

@@ -20,7 +20,7 @@ from twisted.web.resource import Resource
 from twisted.web.server import NOT_DONE_YET
 
 from synapse.api.errors import Codes, SynapseError
-from synapse.crypto.keyring import KeyLookupError, ServerKeyFetcher
+from synapse.crypto.keyring import ServerKeyFetcher
 from synapse.http.server import respond_with_json_bytes, wrap_json_request_handler
 from synapse.http.servlet import parse_integer, parse_json_object_from_request
 
@@ -215,15 +215,7 @@ class RemoteKey(Resource):
                     json_results.add(bytes(result["key_json"]))
 
         if cache_misses and query_remote_on_cache_miss:
-            for server_name, key_ids in cache_misses.items():
-                try:
-                    yield self.fetcher.get_server_verify_key_v2_direct(
-                        server_name, key_ids
-                    )
-                except KeyLookupError as e:
-                    logger.info("Failed to fetch key: %s", e)
-                except Exception:
-                    logger.exception("Failed to get key for %r", server_name)
+            yield self.fetcher.get_keys(cache_misses)
             yield self.query_keys(
                 request, query, query_remote_on_cache_miss=False
             )