1 files changed, 11 insertions, 3 deletions
diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py
index 3fb99f7125..828aced44a 100644
--- a/synapse/crypto/keyring.py
+++ b/synapse/crypto/keyring.py
@@ -22,6 +22,8 @@ from syutil.crypto.signing_key import (
 from syutil.base64util import decode_base64, encode_base64
 from synapse.api.errors import SynapseError, Codes
 
+from synapse.util.retryutils import get_retry_limiter
+
 from OpenSSL import crypto
 
 import logging
@@ -87,12 +89,18 @@ class Keyring(object):
             return
 
         # Try to fetch the key from the remote server.
-        # TODO(markjh): Ratelimit requests to a given server.
 
-        (response, tls_certificate) = yield fetch_server_key(
-            server_name, self.hs.tls_context_factory
+        limiter = yield get_retry_limiter(
+            server_name,
+            self.clock,
+            self.store,
         )
 
+        with limiter:
+            (response, tls_certificate) = yield fetch_server_key(
+                server_name, self.hs.tls_context_factory
+            )
+
         # Check the response.
 
         x509_certificate_bytes = crypto.dump_certificate(