Fixes for the key-notary server

changelog.d/5333.bugfix

@@ -0,0 +1 @@
+Fix various problems which made the signing-key notary server time out for some requests.

synapse/crypto/keyring.py

@@ -46,6 +46,7 @@
 )
 from synapse.storage.keys import FetchKeyResult
 from synapse.util import logcontext, unwrapFirstError
+from synapse.util.async_helpers import yieldable_gather_results
 from synapse.util.logcontext import (
     LoggingContext,
     PreserveLoggingContext,
@@ -169,7 +170,12 @@ def process(server_name, json_object, validity_time):
                     )
                 )
 
-            logger.debug("Verifying for %s with key_ids %s", server_name, key_ids)
+            logger.debug(
+                "Verifying for %s with key_ids %s, min_validity %i",
+                server_name,
+                key_ids,
+                validity_time,
+            )
 
             # add the key request to the queue, but don't start it off yet.
             verify_request = VerifyKeyRequest(
@@ -744,34 +750,50 @@ def __init__(self, hs):
         self.clock = hs.get_clock()
         self.client = hs.get_http_client()
 
-    @defer.inlineCallbacks
     def get_keys(self, keys_to_fetch):
-        """see KeyFetcher.get_keys"""
-        # TODO make this more resilient
-        results = yield logcontext.make_deferred_yieldable(
-            defer.gatherResults(
-                [
-                    run_in_background(
-                        self.get_server_verify_key_v2_direct,
-                        server_name,
-                        server_keys.keys(),
-                    )
-                    for server_name, server_keys in keys_to_fetch.items()
-                ],
-                consumeErrors=True,
-            ).addErrback(unwrapFirstError)
-        )
+        """
+        Args:
+            keys_to_fetch (dict[str, iterable[str]]):
+                the keys to be fetched. server_name -> key_ids
 
-        merged = {}
-        for result in results:
-            merged.update(result)
+        Returns:
+            Deferred[dict[str, dict[str, synapse.storage.keys.FetchKeyResult|None]]]:
+                map from server_name -> key_id -> FetchKeyResult
+        """
+
+        results = {}
 
-        defer.returnValue(
-            {server_name: keys for server_name, keys in merged.items() if keys}
+        @defer.inlineCallbacks
+        def get_key(key_to_fetch_item):
+            server_name, key_ids = key_to_fetch_item
+            try:
+                keys = yield self.get_server_verify_key_v2_direct(server_name, key_ids)
+                results[server_name] = keys
+            except KeyLookupError as e:
+                logger.warning(
+                    "Error looking up keys %s from %s: %s", key_ids, server_name, e
+                )
+            except Exception:
+                logger.exception("Error getting keys %s from %s", key_ids, server_name)
+
+        return yieldable_gather_results(get_key, keys_to_fetch.items()).addCallback(
+            lambda _: results
         )
 
     @defer.inlineCallbacks
     def get_server_verify_key_v2_direct(self, server_name, key_ids):
+        """
+
+        Args:
+            server_name (str):
+            key_ids (iterable[str]):
+
+        Returns:
+            Deferred[dict[str, FetchKeyResult]]: map from key ID to lookup result
+
+        Raises:
+            KeyLookupError if there was a problem making the lookup
+        """
         keys = {}  # type: dict[str, FetchKeyResult]
 
         for requested_key_id in key_ids:
@@ -786,6 +808,19 @@ def get_server_verify_key_v2_direct(self, server_name, key_ids):
                     path="/_matrix/key/v2/server/"
                     + urllib.parse.quote(requested_key_id),
                     ignore_backoff=True,
+
+                    # we only give the remote server 10s to respond. It should be an
+                    # easy request to handle, so if it doesn't reply within 10s, it's
+                    # probably not going to.
+                    #
+                    # Furthermore, when we are acting as a notary server, we cannot
+                    # wait all day for all of the origin servers, as the requesting
+                    # server will otherwise time out before we can respond.
+                    #
+                    # (Note that get_json may make 4 attempts, so this can still take
+                    # almost 45 seconds to fetch the headers, plus up to another 60s to
+                    # read the response).
+                    timeout=10000,
                 )
             except (NotRetryingDestination, RequestSendFailed) as e:
                 raise_from(KeyLookupError("Failed to connect to remote server"), e)
@@ -810,7 +845,7 @@ def get_server_verify_key_v2_direct(self, server_name, key_ids):
             )
             keys.update(response_keys)
 
-        defer.returnValue({server_name: keys})
+        defer.returnValue(keys)
 
 
 @defer.inlineCallbacks

synapse/rest/key/v2/remote_key_resource.py

@@ -20,7 +20,7 @@
 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 @@ def query_keys(self, request, query, query_remote_on_cache_miss=False):
                     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
             )

tests/crypto/test_keyring.py

@@ -25,11 +25,7 @@
 
 from synapse.api.errors import SynapseError
 from synapse.crypto import keyring
-from synapse.crypto.keyring import (
-    KeyLookupError,
-    PerspectivesKeyFetcher,
-    ServerKeyFetcher,
-)
+from synapse.crypto.keyring import PerspectivesKeyFetcher, ServerKeyFetcher
 from synapse.storage.keys import FetchKeyResult
 from synapse.util import logcontext
 from synapse.util.logcontext import LoggingContext
@@ -364,9 +360,11 @@ def get_json(destination, path, **kwargs):
             bytes(res["key_json"]), canonicaljson.encode_canonical_json(response)
         )
 
-        # change the server name: it should cause a rejection
+        # change the server name: the result should be ignored
         response["server_name"] = "OTHER_SERVER"
-        self.get_failure(fetcher.get_keys(keys_to_fetch), KeyLookupError)
+
+        keys = self.get_success(fetcher.get_keys(keys_to_fetch))
+        self.assertEqual(keys, {})
 
 
 class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase):