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Add metrics to track how the rate limiter is affecting requests (sleep/reject) (#13534)

Related to https://github.com/matrix-org/synapse/pull/13499

Part of https://github.com/matrix-org/synapse/issues/13356
This commit is contained in:
Eric Eastwood 2022-08-17 16:10:07 -05:00 committed by GitHub
parent 8bdf2bd31e
commit 49d04e43df
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2 changed files with 30 additions and 8 deletions

1
changelog.d/13534.misc Normal file
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@ -0,0 +1 @@
Add metrics to track how the rate limiter is affecting requests (sleep/reject).

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@ -18,6 +18,8 @@ import logging
import typing
from typing import Any, DefaultDict, Iterator, List, Set
from prometheus_client.core import Counter
from twisted.internet import defer
from synapse.api.errors import LimitExceededError
@ -37,6 +39,9 @@ if typing.TYPE_CHECKING:
logger = logging.getLogger(__name__)
# Track how much the ratelimiter is affecting requests
rate_limit_sleep_counter = Counter("synapse_rate_limit_sleep", "")
rate_limit_reject_counter = Counter("synapse_rate_limit_reject", "")
queue_wait_timer = Histogram(
"synapse_rate_limit_queue_wait_time_seconds",
"sec",
@ -84,7 +89,7 @@ class FederationRateLimiter:
Returns:
context manager which returns a deferred.
"""
return self.ratelimiters[host].ratelimit()
return self.ratelimiters[host].ratelimit(host)
class _PerHostRatelimiter:
@ -119,12 +124,14 @@ class _PerHostRatelimiter:
self.request_times: List[int] = []
@contextlib.contextmanager
def ratelimit(self) -> "Iterator[defer.Deferred[None]]":
def ratelimit(self, host: str) -> "Iterator[defer.Deferred[None]]":
# `contextlib.contextmanager` takes a generator and turns it into a
# context manager. The generator should only yield once with a value
# to be returned by manager.
# Exceptions will be reraised at the yield.
self.host = host
request_id = object()
ret = self._on_enter(request_id)
try:
@ -144,6 +151,8 @@ class _PerHostRatelimiter:
# sleeping or in the ready queue).
queue_size = len(self.ready_request_queue) + len(self.sleeping_requests)
if queue_size > self.reject_limit:
logger.debug("Ratelimiter(%s): rejecting request", self.host)
rate_limit_reject_counter.inc()
raise LimitExceededError(
retry_after_ms=int(self.window_size / self.sleep_limit)
)
@ -155,7 +164,8 @@ class _PerHostRatelimiter:
queue_defer: defer.Deferred[None] = defer.Deferred()
self.ready_request_queue[request_id] = queue_defer
logger.info(
"Ratelimiter: queueing request (queue now %i items)",
"Ratelimiter(%s): queueing request (queue now %i items)",
self.host,
len(self.ready_request_queue),
)
@ -164,19 +174,28 @@ class _PerHostRatelimiter:
return defer.succeed(None)
logger.debug(
"Ratelimit [%s]: len(self.request_times)=%d",
"Ratelimit(%s) [%s]: len(self.request_times)=%d",
self.host,
id(request_id),
len(self.request_times),
)
if len(self.request_times) > self.sleep_limit:
logger.debug("Ratelimiter: sleeping request for %f sec", self.sleep_sec)
logger.debug(
"Ratelimiter(%s) [%s]: sleeping request for %f sec",
self.host,
id(request_id),
self.sleep_sec,
)
rate_limit_sleep_counter.inc()
ret_defer = run_in_background(self.clock.sleep, self.sleep_sec)
self.sleeping_requests.add(request_id)
def on_wait_finished(_: Any) -> "defer.Deferred[None]":
logger.debug("Ratelimit [%s]: Finished sleeping", id(request_id))
logger.debug(
"Ratelimit(%s) [%s]: Finished sleeping", self.host, id(request_id)
)
self.sleeping_requests.discard(request_id)
queue_defer = queue_request()
return queue_defer
@ -186,7 +205,9 @@ class _PerHostRatelimiter:
ret_defer = queue_request()
def on_start(r: object) -> object:
logger.debug("Ratelimit [%s]: Processing req", id(request_id))
logger.debug(
"Ratelimit(%s) [%s]: Processing req", self.host, id(request_id)
)
self.current_processing.add(request_id)
return r
@ -217,7 +238,7 @@ class _PerHostRatelimiter:
return make_deferred_yieldable(ret_defer)
def _on_exit(self, request_id: object) -> None:
logger.debug("Ratelimit [%s]: Processed req", id(request_id))
logger.debug("Ratelimit(%s) [%s]: Processed req", self.host, id(request_id))
self.current_processing.discard(request_id)
try:
# start processing the next item on the queue.