Describe which rate limiter was hit in logs (#16135)

Author: David Robertson

changelog.d/16135.misc

@@ -0,0 +1 @@
+Describe which rate limiter was hit in logs.

synapse/api/errors.py

@@ -211,6 +211,11 @@ def __init__(
     def error_dict(self, config: Optional["HomeServerConfig"]) -> "JsonDict":
         return cs_error(self.msg, self.errcode, **self._additional_fields)
 
+    @property
+    def debug_context(self) -> Optional[str]:
+        """Override this to add debugging context that shouldn't be sent to clients."""
+        return None
+
 
 class InvalidAPICallError(SynapseError):
     """You called an existing API endpoint, but fed that endpoint
@@ -508,8 +513,8 @@ class LimitExceededError(SynapseError):
 
     def __init__(
         self,
+        limiter_name: str,
         code: int = 429,
-        msg: str = "Too Many Requests",
         retry_after_ms: Optional[int] = None,
         errcode: str = Codes.LIMIT_EXCEEDED,
     ):
@@ -518,12 +523,17 @@ def __init__(
             if self.include_retry_after_header and retry_after_ms is not None
             else None
         )
-        super().__init__(code, msg, errcode, headers=headers)
+        super().__init__(code, "Too Many Requests", errcode, headers=headers)
         self.retry_after_ms = retry_after_ms
+        self.limiter_name = limiter_name
 
     def error_dict(self, config: Optional["HomeServerConfig"]) -> "JsonDict":
         return cs_error(self.msg, self.errcode, retry_after_ms=self.retry_after_ms)
 
+    @property
+    def debug_context(self) -> Optional[str]:
+        return self.limiter_name
+
 
 class RoomKeysVersionError(SynapseError):
     """A client has tried to upload to a non-current version of the room_keys store"""

synapse/api/ratelimiting.py

@@ -61,12 +61,16 @@ class Ratelimiter:
     """
 
     def __init__(
-        self, store: DataStore, clock: Clock, rate_hz: float, burst_count: int
+        self,
+        store: DataStore,
+        clock: Clock,
+        cfg: RatelimitSettings,
     ):
         self.clock = clock
-        self.rate_hz = rate_hz
-        self.burst_count = burst_count
+        self.rate_hz = cfg.per_second
+        self.burst_count = cfg.burst_count
         self.store = store
+        self._limiter_name = cfg.key
 
         # An ordered dictionary representing the token buckets tracked by this rate
         # limiter. Each entry maps a key of arbitrary type to a tuple representing:
@@ -305,7 +309,8 @@ async def ratelimit(
 
         if not allowed:
             raise LimitExceededError(
-                retry_after_ms=int(1000 * (time_allowed - time_now_s))
+                limiter_name=self._limiter_name,
+                retry_after_ms=int(1000 * (time_allowed - time_now_s)),
             )
 
 
@@ -322,7 +327,9 @@ def __init__(
 
         # The rate_hz and burst_count are overridden on a per-user basis
         self.request_ratelimiter = Ratelimiter(
-            store=self.store, clock=self.clock, rate_hz=0, burst_count=0
+            store=self.store,
+            clock=self.clock,
+            cfg=RatelimitSettings(key=rc_message.key, per_second=0, burst_count=0),
         )
         self._rc_message = rc_message
 
@@ -332,8 +339,7 @@ def __init__(
             self.admin_redaction_ratelimiter: Optional[Ratelimiter] = Ratelimiter(
                 store=self.store,
                 clock=self.clock,
-                rate_hz=rc_admin_redaction.per_second,
-                burst_count=rc_admin_redaction.burst_count,
+                cfg=rc_admin_redaction,
             )
         else:
             self.admin_redaction_ratelimiter = None

synapse/config/ratelimiting.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Dict, Optional
+from typing import Any, Dict, Optional, cast
 
 import attr
 
@@ -21,16 +21,47 @@
 from ._base import Config
 
 
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class RatelimitSettings:
-    def __init__(
-        self,
-        config: Dict[str, float],
+    key: str
+    per_second: float
+    burst_count: int
+
+    @classmethod
+    def parse(
+        cls,
+        config: Dict[str, Any],
+        key: str,
         defaults: Optional[Dict[str, float]] = None,
-    ):
+    ) -> "RatelimitSettings":
+        """Parse config[key] as a new-style rate limiter config.
+
+        The key may refer to a nested dictionary using a full stop (.) to separate
+        each nested key. For example, use the key "a.b.c" to parse the following:
+
+        a:
+          b:
+            c:
+              per_second: 10
+              burst_count: 200
+
+        If this lookup fails, we'll fallback to the defaults.
+        """
         defaults = defaults or {"per_second": 0.17, "burst_count": 3.0}
 
-        self.per_second = config.get("per_second", defaults["per_second"])
-        self.burst_count = int(config.get("burst_count", defaults["burst_count"]))
+        rl_config = config
+        for part in key.split("."):
+            rl_config = rl_config.get(part, {})
+
+        # By this point we should have hit the rate limiter parameters.
+        # We don't actually check this though!
+        rl_config = cast(Dict[str, float], rl_config)
+
+        return cls(
+            key=key,
+            per_second=rl_config.get("per_second", defaults["per_second"]),
+            burst_count=int(rl_config.get("burst_count", defaults["burst_count"])),
+        )
 
 
 @attr.s(auto_attribs=True)
@@ -49,15 +80,14 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         # Load the new-style messages config if it exists. Otherwise fall back
         # to the old method.
         if "rc_message" in config:
-            self.rc_message = RatelimitSettings(
-                config["rc_message"], defaults={"per_second": 0.2, "burst_count": 10.0}
+            self.rc_message = RatelimitSettings.parse(
+                config, "rc_message", defaults={"per_second": 0.2, "burst_count": 10.0}
             )
         else:
             self.rc_message = RatelimitSettings(
-                {
-                    "per_second": config.get("rc_messages_per_second", 0.2),
-                    "burst_count": config.get("rc_message_burst_count", 10.0),
-                }
+                key="rc_messages",
+                per_second=config.get("rc_messages_per_second", 0.2),
+                burst_count=config.get("rc_message_burst_count", 10.0),
             )
 
         # Load the new-style federation config, if it exists. Otherwise, fall
@@ -79,51 +109,59 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
                 }
             )
 
-        self.rc_registration = RatelimitSettings(config.get("rc_registration", {}))
+        self.rc_registration = RatelimitSettings.parse(config, "rc_registration", {})
 
-        self.rc_registration_token_validity = RatelimitSettings(
-            config.get("rc_registration_token_validity", {}),
+        self.rc_registration_token_validity = RatelimitSettings.parse(
+            config,
+            "rc_registration_token_validity",
             defaults={"per_second": 0.1, "burst_count": 5},
         )
 
         # It is reasonable to login with a bunch of devices at once (i.e. when
         # setting up an account), but it is *not* valid to continually be
         # logging into new devices.
-        rc_login_config = config.get("rc_login", {})
-        self.rc_login_address = RatelimitSettings(
-            rc_login_config.get("address", {}),
+        self.rc_login_address = RatelimitSettings.parse(
+            config,
+            "rc_login.address",
             defaults={"per_second": 0.003, "burst_count": 5},
         )
-        self.rc_login_account = RatelimitSettings(
-            rc_login_config.get("account", {}),
+        self.rc_login_account = RatelimitSettings.parse(
+            config,
+            "rc_login.account",
             defaults={"per_second": 0.003, "burst_count": 5},
         )
-        self.rc_login_failed_attempts = RatelimitSettings(
-            rc_login_config.get("failed_attempts", {})
+        self.rc_login_failed_attempts = RatelimitSettings.parse(
+            config,
+            "rc_login.failed_attempts",
+            {},
         )
 
         self.federation_rr_transactions_per_room_per_second = config.get(
             "federation_rr_transactions_per_room_per_second", 50
         )
 
-        rc_admin_redaction = config.get("rc_admin_redaction")
         self.rc_admin_redaction = None
-        if rc_admin_redaction:
-            self.rc_admin_redaction = RatelimitSettings(rc_admin_redaction)
+        if "rc_admin_redaction" in config:
+            self.rc_admin_redaction = RatelimitSettings.parse(
+                config, "rc_admin_redaction", {}
+            )
 
-        self.rc_joins_local = RatelimitSettings(
-            config.get("rc_joins", {}).get("local", {}),
+        self.rc_joins_local = RatelimitSettings.parse(
+            config,
+            "rc_joins.local",
             defaults={"per_second": 0.1, "burst_count": 10},
         )
-        self.rc_joins_remote = RatelimitSettings(
-            config.get("rc_joins", {}).get("remote", {}),
+        self.rc_joins_remote = RatelimitSettings.parse(
+            config,
+            "rc_joins.remote",
             defaults={"per_second": 0.01, "burst_count": 10},
         )
 
         # Track the rate of joins to a given room. If there are too many, temporarily
         # prevent local joins and remote joins via this server.
-        self.rc_joins_per_room = RatelimitSettings(
-            config.get("rc_joins_per_room", {}),
+        self.rc_joins_per_room = RatelimitSettings.parse(
+            config,
+            "rc_joins_per_room",
             defaults={"per_second": 1, "burst_count": 10},
         )
 
@@ -132,31 +170,37 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         # * For requests received over federation this is keyed by the origin.
         #
         # Note that this isn't exposed in the configuration as it is obscure.
-        self.rc_key_requests = RatelimitSettings(
-            config.get("rc_key_requests", {}),
+        self.rc_key_requests = RatelimitSettings.parse(
+            config,
+            "rc_key_requests",
             defaults={"per_second": 20, "burst_count": 100},
         )
 
-        self.rc_3pid_validation = RatelimitSettings(
-            config.get("rc_3pid_validation") or {},
+        self.rc_3pid_validation = RatelimitSettings.parse(
+            config,
+            "rc_3pid_validation",
             defaults={"per_second": 0.003, "burst_count": 5},
         )
 
-        self.rc_invites_per_room = RatelimitSettings(
-            config.get("rc_invites", {}).get("per_room", {}),
+        self.rc_invites_per_room = RatelimitSettings.parse(
+            config,
+            "rc_invites.per_room",
             defaults={"per_second": 0.3, "burst_count": 10},
         )
-        self.rc_invites_per_user = RatelimitSettings(
-            config.get("rc_invites", {}).get("per_user", {}),
+        self.rc_invites_per_user = RatelimitSettings.parse(
+            config,
+            "rc_invites.per_user",
             defaults={"per_second": 0.003, "burst_count": 5},
         )
 
-        self.rc_invites_per_issuer = RatelimitSettings(
-            config.get("rc_invites", {}).get("per_issuer", {}),
+        self.rc_invites_per_issuer = RatelimitSettings.parse(
+            config,
+            "rc_invites.per_issuer",
             defaults={"per_second": 0.3, "burst_count": 10},
         )
 
-        self.rc_third_party_invite = RatelimitSettings(
-            config.get("rc_third_party_invite", {}),
+        self.rc_third_party_invite = RatelimitSettings.parse(
+            config,
+            "rc_third_party_invite",
             defaults={"per_second": 0.0025, "burst_count": 5},
         )

synapse/handlers/auth.py

@@ -218,19 +218,17 @@ def __init__(self, hs: "HomeServer"):
         self._failed_uia_attempts_ratelimiter = Ratelimiter(
             store=self.store,
             clock=self.clock,
-            rate_hz=self.hs.config.ratelimiting.rc_login_failed_attempts.per_second,
-            burst_count=self.hs.config.ratelimiting.rc_login_failed_attempts.burst_count,
+            cfg=self.hs.config.ratelimiting.rc_login_failed_attempts,
         )
 
         # The number of seconds to keep a UI auth session active.
         self._ui_auth_session_timeout = hs.config.auth.ui_auth_session_timeout
 
-        # Ratelimitier for failed /login attempts
+        # Ratelimiter for failed /login attempts
         self._failed_login_attempts_ratelimiter = Ratelimiter(
             store=self.store,
             clock=hs.get_clock(),
-            rate_hz=self.hs.config.ratelimiting.rc_login_failed_attempts.per_second,
-            burst_count=self.hs.config.ratelimiting.rc_login_failed_attempts.burst_count,
+            cfg=self.hs.config.ratelimiting.rc_login_failed_attempts,
         )
 
         self._clock = self.hs.get_clock()

synapse/handlers/devicemessage.py

@@ -90,8 +90,7 @@ def __init__(self, hs: "HomeServer"):
         self._ratelimiter = Ratelimiter(
             store=self.store,
             clock=hs.get_clock(),
-            rate_hz=hs.config.ratelimiting.rc_key_requests.per_second,
-            burst_count=hs.config.ratelimiting.rc_key_requests.burst_count,
+            cfg=hs.config.ratelimiting.rc_key_requests,
         )
 
     async def on_direct_to_device_edu(self, origin: str, content: JsonDict) -> None:

synapse/handlers/identity.py

@@ -66,14 +66,12 @@ def __init__(self, hs: "HomeServer"):
         self._3pid_validation_ratelimiter_ip = Ratelimiter(
             store=self.store,
             clock=hs.get_clock(),
-            rate_hz=hs.config.ratelimiting.rc_3pid_validation.per_second,
-            burst_count=hs.config.ratelimiting.rc_3pid_validation.burst_count,
+            cfg=hs.config.ratelimiting.rc_3pid_validation,
         )
         self._3pid_validation_ratelimiter_address = Ratelimiter(
             store=self.store,
             clock=hs.get_clock(),
-            rate_hz=hs.config.ratelimiting.rc_3pid_validation.per_second,
-            burst_count=hs.config.ratelimiting.rc_3pid_validation.burst_count,
+            cfg=hs.config.ratelimiting.rc_3pid_validation,
         )
 
     async def ratelimit_request_token_requests(