Merge pull request #4542 from matrix-org/rav/cache_for_bad_well_known

Caching for invalid .well-knowns
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Richard van der Hoff 2019-02-01 11:20:07 +00:00 committed by GitHub
commit 582786fbf2
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2 changed files with 59 additions and 17 deletions

1
changelog.d/4542.misc Normal file
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@ -0,0 +1 @@
Improve performance of handling servers with invalid .well-known

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@ -23,14 +23,17 @@ from zope.interface import implementer
from twisted.internet import defer
from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
from twisted.internet.interfaces import IStreamClientEndpoint
from twisted.web.client import URI, Agent, HTTPConnectionPool, RedirectAgent, readBody
from twisted.web.http import stringToDatetime
from twisted.web.http_headers import Headers
from twisted.web.iweb import IAgent
from synapse.http.federation.srv_resolver import SrvResolver, pick_server_from_list
from synapse.util import Clock
from synapse.util.caches.ttlcache import TTLCache
from synapse.util.logcontext import make_deferred_yieldable
from synapse.util.metrics import Measure
# period to cache .well-known results for by default
WELL_KNOWN_DEFAULT_CACHE_PERIOD = 24 * 3600
@ -44,6 +47,8 @@ WELL_KNOWN_INVALID_CACHE_PERIOD = 1 * 3600
# cap for .well-known cache period
WELL_KNOWN_MAX_CACHE_PERIOD = 48 * 3600
# magic value to mark an invalid well-known
INVALID_WELL_KNOWN = object()
logger = logging.getLogger(__name__)
well_known_cache = TTLCache('well-known')
@ -78,6 +83,8 @@ class MatrixFederationAgent(object):
_well_known_cache=well_known_cache,
):
self._reactor = reactor
self._clock = Clock(reactor)
self._tls_client_options_factory = tls_client_options_factory
if _srv_resolver is None:
_srv_resolver = SrvResolver()
@ -98,6 +105,11 @@ class MatrixFederationAgent(object):
)
self._well_known_agent = _well_known_agent
# our cache of .well-known lookup results, mapping from server name
# to delegated name. The values can be:
# `bytes`: a valid server-name
# `None`: there is no .well-known here
# INVALID_WELL_KNWOWN: the .well-known here is invalid
self._well_known_cache = _well_known_cache
@defer.inlineCallbacks
@ -152,12 +164,9 @@ class MatrixFederationAgent(object):
class EndpointFactory(object):
@staticmethod
def endpointForURI(_uri):
logger.info(
"Connecting to %s:%i",
res.target_host.decode("ascii"),
res.target_port,
ep = LoggingHostnameEndpoint(
self._reactor, res.target_host, res.target_port,
)
ep = HostnameEndpoint(self._reactor, res.target_host, res.target_port)
if tls_options is not None:
ep = wrapClientTLS(tls_options, ep)
return ep
@ -283,14 +292,35 @@ class MatrixFederationAgent(object):
None if there was no .well-known file.
"""
try:
cached = self._well_known_cache[server_name]
defer.returnValue(cached)
result = self._well_known_cache[server_name]
except KeyError:
pass
# TODO: should we linearise so that we don't end up doing two .well-known
# requests for the same server in parallel?
with Measure(self._clock, "get_well_known"):
result, cache_period = yield self._do_get_well_known(server_name)
# TODO: should we linearise so that we don't end up doing two .well-known requests
# for the same server in parallel?
if cache_period > 0:
self._well_known_cache.set(server_name, result, cache_period)
if result == INVALID_WELL_KNOWN:
raise Exception("invalid .well-known on this server")
defer.returnValue(result)
@defer.inlineCallbacks
def _do_get_well_known(self, server_name):
"""Actually fetch and parse a .well-known, without checking the cache
Args:
server_name (bytes): name of the server, from the requested url
Returns:
Deferred[Tuple[bytes|None|object],int]:
result, cache period, where result is one of:
- the new server name from the .well-known (as a `bytes`)
- None if there was no .well-known file.
- INVALID_WELL_KNOWN if the .well-known was invalid
"""
uri = b"https://%s/.well-known/matrix/server" % (server_name, )
uri_str = uri.decode("ascii")
logger.info("Fetching %s", uri_str)
@ -308,9 +338,7 @@ class MatrixFederationAgent(object):
# after startup
cache_period = WELL_KNOWN_INVALID_CACHE_PERIOD
cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)
self._well_known_cache.set(server_name, None, cache_period)
defer.returnValue(None)
defer.returnValue((None, cache_period))
try:
parsed_body = json.loads(body.decode('utf-8'))
@ -320,7 +348,10 @@ class MatrixFederationAgent(object):
if "m.server" not in parsed_body:
raise Exception("Missing key 'm.server'")
except Exception as e:
raise Exception("invalid .well-known response from %s: %s" % (uri_str, e,))
logger.info("invalid .well-known response from %s: %s", uri_str, e)
cache_period = WELL_KNOWN_INVALID_CACHE_PERIOD
cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)
defer.returnValue((INVALID_WELL_KNOWN, cache_period))
result = parsed_body["m.server"].encode("ascii")
@ -336,10 +367,20 @@ class MatrixFederationAgent(object):
else:
cache_period = min(cache_period, WELL_KNOWN_MAX_CACHE_PERIOD)
if cache_period > 0:
self._well_known_cache.set(server_name, result, cache_period)
defer.returnValue((result, cache_period))
defer.returnValue(result)
@implementer(IStreamClientEndpoint)
class LoggingHostnameEndpoint(object):
"""A wrapper for HostnameEndpint which logs when it connects"""
def __init__(self, reactor, host, port, *args, **kwargs):
self.host = host
self.port = port
self.ep = HostnameEndpoint(reactor, host, port, *args, **kwargs)
def connect(self, protocol_factory):
logger.info("Connecting to %s:%i", self.host, self.port)
return self.ep.connect(protocol_factory)
def _cache_period_from_headers(headers, time_now=time.time):