Avoid raising the body exceeded error multiple times. (#9108)

Previously this code generated unreferenced `Deferred` instances
which caused "Unhandled Deferreds" errors to appear in error
situations.
This commit is contained in:
Patrick Cloke 2021-01-15 11:00:13 -05:00 committed by GitHub
parent 9ffac2bef1
commit 74dd906041
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4 changed files with 115 additions and 3 deletions

1
changelog.d/9108.bugfix Normal file
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@ -0,0 +1 @@
Fix "Unhandled error in Deferred: BodyExceededMaxSize" errors when .well-known files that are too large.

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@ -766,14 +766,24 @@ class _ReadBodyWithMaxSizeProtocol(protocol.Protocol):
self.max_size = max_size
def dataReceived(self, data: bytes) -> None:
# If the deferred was called, bail early.
if self.deferred.called:
return
self.stream.write(data)
self.length += len(data)
# The first time the maximum size is exceeded, error and cancel the
# connection. dataReceived might be called again if data was received
# in the meantime.
if self.max_size is not None and self.length >= self.max_size:
self.deferred.errback(BodyExceededMaxSize())
self.deferred = defer.Deferred()
self.transport.loseConnection()
def connectionLost(self, reason: Failure) -> None:
# If the maximum size was already exceeded, there's nothing to do.
if self.deferred.called:
return
if reason.check(ResponseDone):
self.deferred.callback(self.length)
elif reason.check(PotentialDataLoss):

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@ -1095,7 +1095,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
# Expire both caches and repeat the request
self.reactor.pump((10000.0,))
# Repated the request, this time it should fail if the lookup fails.
# Repeat the request, this time it should fail if the lookup fails.
fetch_d = defer.ensureDeferred(
self.well_known_resolver.get_well_known(b"testserv")
)
@ -1130,7 +1130,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
content=b'{ "m.server": "' + (b"a" * WELL_KNOWN_MAX_SIZE) + b'" }',
)
# The result is sucessful, but disabled delegation.
# The result is successful, but disabled delegation.
r = self.successResultOf(fetch_d)
self.assertIsNone(r.delegated_server)

101
tests/http/test_client.py Normal file
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@ -0,0 +1,101 @@
# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from io import BytesIO
from mock import Mock
from twisted.python.failure import Failure
from twisted.web.client import ResponseDone
from synapse.http.client import BodyExceededMaxSize, read_body_with_max_size
from tests.unittest import TestCase
class ReadBodyWithMaxSizeTests(TestCase):
def setUp(self):
"""Start reading the body, returns the response, result and proto"""
self.response = Mock()
self.result = BytesIO()
self.deferred = read_body_with_max_size(self.response, self.result, 6)
# Fish the protocol out of the response.
self.protocol = self.response.deliverBody.call_args[0][0]
self.protocol.transport = Mock()
def _cleanup_error(self):
"""Ensure that the error in the Deferred is handled gracefully."""
called = [False]
def errback(f):
called[0] = True
self.deferred.addErrback(errback)
self.assertTrue(called[0])
def test_no_error(self):
"""A response that is NOT too large."""
# Start sending data.
self.protocol.dataReceived(b"12345")
# Close the connection.
self.protocol.connectionLost(Failure(ResponseDone()))
self.assertEqual(self.result.getvalue(), b"12345")
self.assertEqual(self.deferred.result, 5)
def test_too_large(self):
"""A response which is too large raises an exception."""
# Start sending data.
self.protocol.dataReceived(b"1234567890")
# Close the connection.
self.protocol.connectionLost(Failure(ResponseDone()))
self.assertEqual(self.result.getvalue(), b"1234567890")
self.assertIsInstance(self.deferred.result, Failure)
self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
self._cleanup_error()
def test_multiple_packets(self):
"""Data should be accummulated through mutliple packets."""
# Start sending data.
self.protocol.dataReceived(b"12")
self.protocol.dataReceived(b"34")
# Close the connection.
self.protocol.connectionLost(Failure(ResponseDone()))
self.assertEqual(self.result.getvalue(), b"1234")
self.assertEqual(self.deferred.result, 4)
def test_additional_data(self):
"""A connection can receive data after being closed."""
# Start sending data.
self.protocol.dataReceived(b"1234567890")
self.assertIsInstance(self.deferred.result, Failure)
self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
self.protocol.transport.loseConnection.assert_called_once()
# More data might have come in.
self.protocol.dataReceived(b"1234567890")
# Close the connection.
self.protocol.connectionLost(Failure(ResponseDone()))
self.assertEqual(self.result.getvalue(), b"1234567890")
self.assertIsInstance(self.deferred.result, Failure)
self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
self._cleanup_error()