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

2 files changed, 25 insertions, 9 deletions

diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index 578e798773..fdb2955be8 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -211,6 +211,11 @@ class SynapseError(CodeMessageException):
     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 @@ class LimitExceededError(SynapseError):
             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"""
diff --git a/synapse/api/ratelimiting.py b/synapse/api/ratelimiting.py
index 511790c7c5..887b214d64 100644
--- a/synapse/api/ratelimiting.py
+++ b/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 @@ class Ratelimiter:
 
         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 @@ class RequestRatelimiter:
 
         # 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 @@ class RequestRatelimiter:
             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