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Fix race for concurrent downloads of remote media. (#8682)

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Fixes #6755
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Erik Johnston 2020-10-30 10:55:24 +00:00 committed by GitHub
parent 4504151546
commit 46f4be94b4
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6 changed files with 429 additions and 69 deletions
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1
changelog.d/8682.bugfix Normal file
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@ -0,0 +1 @@
Fix exception during handling multiple concurrent requests for remote media when using multiple media repositories.

83
synapse/rest/media/v1/media_repository.py
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@ -305,15 +305,12 @@ class MediaRepository:
# file_id is the ID we use to track the file locally. If we've already
# seen the file then reuse the existing ID, otherwise genereate a new
# one.
if media_info:
file_id = media_info["filesystem_id"]
else:
file_id = random_string(24)
file_info = FileInfo(server_name, file_id)
# If we have an entry in the DB, try and look for it
if media_info:
file_id = media_info["filesystem_id"]
file_info = FileInfo(server_name, file_id)
if media_info["quarantined_by"]:
logger.info("Media is quarantined")
raise NotFoundError()
@ -324,14 +321,34 @@ class MediaRepository:
# Failed to find the file anywhere, lets download it.
media_info = await self._download_remote_file(server_name, media_id, file_id)
try:
media_info = await self._download_remote_file(server_name, media_id,)
except SynapseError:
raise
except Exception as e:
# An exception may be because we downloaded media in another
# process, so let's check if we magically have the media.
media_info = await self.store.get_cached_remote_media(server_name, media_id)
if not media_info:
raise e
file_id = media_info["filesystem_id"]
file_info = FileInfo(server_name, file_id)
# We generate thumbnails even if another process downloaded the media
# as a) it's conceivable that the other download request dies before it
# generates thumbnails, but mainly b) we want to be sure the thumbnails
# have finished being generated before responding to the client,
# otherwise they'll request thumbnails and get a 404 if they're not
# ready yet.
await self._generate_thumbnails(
server_name, media_id, file_id, media_info["media_type"]
)
responder = await self.media_storage.fetch_media(file_info)
return responder, media_info
async def _download_remote_file(
self, server_name: str, media_id: str, file_id: str
) -> dict:
async def _download_remote_file(self, server_name: str, media_id: str,) -> dict:
"""Attempt to download the remote file from the given server name,
using the given file_id as the local id.
@ -346,6 +363,8 @@ class MediaRepository:
The media info of the file.
"""
file_id = random_string(24)
file_info = FileInfo(server_name=server_name, file_id=file_id)
with self.media_storage.store_into_file(file_info) as (f, fname, finish):
@ -405,8 +424,16 @@ class MediaRepository:
upload_name = get_filename_from_headers(headers)
time_now_ms = self.clock.time_msec()
logger.info("Stored remote media in file %r", fname)
# Multiple remote media download requests can race (when using
# multiple media repos), so this may throw a violation constraint
# exception. If it does we'll delete the newly downloaded file from
# disk (as we're in the ctx manager).
#
# However: we've already called `finish()` so we may have also
# written to the storage providers. This is preferable to the
# alternative where we call `finish()` *after* this, where we could
# end up having an entry in the DB but fail to write the files to
# the storage providers.
await self.store.store_cached_remote_media(
origin=server_name,
media_id=media_id,
@ -417,6 +444,8 @@ class MediaRepository:
filesystem_id=file_id,
)
logger.info("Stored remote media in file %r", fname)
media_info = {
"media_type": media_type,
"media_length": length,
@ -425,8 +454,6 @@ class MediaRepository:
"filesystem_id": file_id,
}
await self._generate_thumbnails(server_name, media_id, file_id, media_type)
return media_info
def _get_thumbnail_requirements(self, media_type):
@ -692,7 +719,6 @@ class MediaRepository:
if not t_byte_source:
continue
try:
file_info = FileInfo(
server_name=server_name,
file_id=file_id,
@ -704,16 +730,29 @@ class MediaRepository:
url_cache=url_cache,
)
output_path = await self.media_storage.store_file(
t_byte_source, file_info
)
with self.media_storage.store_into_file(file_info) as (f, fname, finish):
try:
await self.media_storage.write_to_file(t_byte_source, f)
await finish()
finally:
t_byte_source.close()
t_len = os.path.getsize(output_path)
t_len = os.path.getsize(fname)
# Write to database
if server_name:
# Multiple remote media download requests can race (when
# using multiple media repos), so this may throw a violation
# constraint exception. If it does we'll delete the newly
# generated thumbnail from disk (as we're in the ctx
# manager).
#
# However: we've already called `finish()` so we may have
# also written to the storage providers. This is preferable
# to the alternative where we call `finish()` *after* this,
# where we could end up having an entry in the DB but fail
# to write the files to the storage providers.
try:
await self.store.store_remote_media_thumbnail(
server_name,
media_id,
@ -724,6 +763,12 @@ class MediaRepository:
t_method,
t_len,
)
except Exception as e:
thumbnail_exists = await self.store.get_remote_media_thumbnail(
server_name, media_id, t_width, t_height, t_type,
)
if not thumbnail_exists:
raise e
else:
await self.store.store_local_thumbnail(
media_id, t_width, t_height, t_type, t_method, t_len

22
synapse/rest/media/v1/media_storage.py
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@ -52,6 +52,7 @@ class MediaStorage:
storage_providers: Sequence["StorageProviderWrapper"],
):
self.hs = hs
self.reactor = hs.get_reactor()
self.local_media_directory = local_media_directory
self.filepaths = filepaths
self.storage_providers = storage_providers
@ -70,13 +71,16 @@ class MediaStorage:
with self.store_into_file(file_info) as (f, fname, finish_cb):
# Write to the main repository
await defer_to_thread(
self.hs.get_reactor(), _write_file_synchronously, source, f
)
await self.write_to_file(source, f)
await finish_cb()
return fname
async def write_to_file(self, source: IO, output: IO):
"""Asynchronously write the `source` to `output`.
"""
await defer_to_thread(self.reactor, _write_file_synchronously, source, output)
@contextlib.contextmanager
def store_into_file(self, file_info: FileInfo):
"""Context manager used to get a file like object to write into, as
@ -112,14 +116,20 @@ class MediaStorage:
finished_called = [False]
try:
with open(fname, "wb") as f:
async def finish():
# Ensure that all writes have been flushed and close the
# file.
f.flush()
f.close()
for provider in self.storage_providers:
await provider.store_file(path, file_info)
finished_called[0] = True
try:
with open(fname, "wb") as f:
yield f, fname, finish
except Exception:
try:
@ -210,7 +220,7 @@ class MediaStorage:
if res:
with res:
consumer = BackgroundFileConsumer(
open(local_path, "wb"), self.hs.get_reactor()
open(local_path, "wb"), self.reactor
)
await res.write_to_consumer(consumer)
await consumer.wait()

27
synapse/storage/databases/main/media_repository.py
View File

@ -452,6 +452,33 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
desc="get_remote_media_thumbnails",
)
async def get_remote_media_thumbnail(
self, origin: str, media_id: str, t_width: int, t_height: int, t_type: str,
) -> Optional[Dict[str, Any]]:
"""Fetch the thumbnail info of given width, height and type.
"""
return await self.db_pool.simple_select_one(
table="remote_media_cache_thumbnails",
keyvalues={
"media_origin": origin,
"media_id": media_id,
"thumbnail_width": t_width,
"thumbnail_height": t_height,
"thumbnail_type": t_type,
},
retcols=(
"thumbnail_width",
"thumbnail_height",
"thumbnail_method",
"thumbnail_type",
"thumbnail_length",
"filesystem_id",
),
allow_none=True,
desc="get_remote_media_thumbnail",
)
async def store_remote_media_thumbnail(
self,
origin,

277
tests/replication/test_multi_media_repo.py Normal file
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@ -0,0 +1,277 @@
# -*- coding: utf-8 -*-
# Copyright 2020 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.
import logging
import os
from binascii import unhexlify
from typing import Tuple
from twisted.internet.protocol import Factory
from twisted.protocols.tls import TLSMemoryBIOFactory
from twisted.web.http import HTTPChannel
from twisted.web.server import Request
from synapse.rest import admin
from synapse.rest.client.v1 import login
from synapse.server import HomeServer
from tests.http import TestServerTLSConnectionFactory, get_test_ca_cert_file
from tests.replication._base import BaseMultiWorkerStreamTestCase
from tests.server import FakeChannel, FakeTransport
logger = logging.getLogger(__name__)
test_server_connection_factory = None
class MediaRepoShardTestCase(BaseMultiWorkerStreamTestCase):
"""Checks running multiple media repos work correctly.
"""
servlets = [
admin.register_servlets_for_client_rest_resource,
login.register_servlets,
]
def prepare(self, reactor, clock, hs):
self.user_id = self.register_user("user", "pass")
self.access_token = self.login("user", "pass")
self.reactor.lookups["example.com"] = "127.0.0.2"
def default_config(self):
conf = super().default_config()
conf["federation_custom_ca_list"] = [get_test_ca_cert_file()]
return conf
def _get_media_req(
self, hs: HomeServer, target: str, media_id: str
) -> Tuple[FakeChannel, Request]:
"""Request some remote media from the given HS by calling the download
API.
This then triggers an outbound request from the HS to the target.
Returns:
The channel for the *client* request and the *outbound* request for
the media which the caller should respond to.
"""
request, channel = self.make_request(
"GET",
"/{}/{}".format(target, media_id),
shorthand=False,
access_token=self.access_token,
)
request.render(hs.get_media_repository_resource().children[b"download"])
self.pump()
clients = self.reactor.tcpClients
self.assertGreaterEqual(len(clients), 1)
(host, port, client_factory, _timeout, _bindAddress) = clients.pop()
# build the test server
server_tls_protocol = _build_test_server(get_connection_factory())
# now, tell the client protocol factory to build the client protocol (it will be a
# _WrappingProtocol, around a TLSMemoryBIOProtocol, around an
# HTTP11ClientProtocol) and wire the output of said protocol up to the server via
# a FakeTransport.
#
# Normally this would be done by the TCP socket code in Twisted, but we are
# stubbing that out here.
client_protocol = client_factory.buildProtocol(None)
client_protocol.makeConnection(
FakeTransport(server_tls_protocol, self.reactor, client_protocol)
)
# tell the server tls protocol to send its stuff back to the client, too
server_tls_protocol.makeConnection(
FakeTransport(client_protocol, self.reactor, server_tls_protocol)
)
# fish the test server back out of the server-side TLS protocol.
http_server = server_tls_protocol.wrappedProtocol
# give the reactor a pump to get the TLS juices flowing.
self.reactor.pump((0.1,))
self.assertEqual(len(http_server.requests), 1)
request = http_server.requests[0]
self.assertEqual(request.method, b"GET")
self.assertEqual(
request.path,
"/_matrix/media/r0/download/{}/{}".format(target, media_id).encode("utf-8"),
)
self.assertEqual(
request.requestHeaders.getRawHeaders(b"host"), [target.encode("utf-8")]
)
return channel, request
def test_basic(self):
"""Test basic fetching of remote media from a single worker.
"""
hs1 = self.make_worker_hs("synapse.app.generic_worker")
channel, request = self._get_media_req(hs1, "example.com:443", "ABC123")
request.setResponseCode(200)
request.responseHeaders.setRawHeaders(b"Content-Type", [b"text/plain"])
request.write(b"Hello!")
request.finish()
self.pump(0.1)
self.assertEqual(channel.code, 200)
self.assertEqual(channel.result["body"], b"Hello!")
def test_download_simple_file_race(self):
"""Test that fetching remote media from two different processes at the
same time works.
"""
hs1 = self.make_worker_hs("synapse.app.generic_worker")
hs2 = self.make_worker_hs("synapse.app.generic_worker")
start_count = self._count_remote_media()
# Make two requests without responding to the outbound media requests.
channel1, request1 = self._get_media_req(hs1, "example.com:443", "ABC123")
channel2, request2 = self._get_media_req(hs2, "example.com:443", "ABC123")
# Respond to the first outbound media request and check that the client
# request is successful
request1.setResponseCode(200)
request1.responseHeaders.setRawHeaders(b"Content-Type", [b"text/plain"])
request1.write(b"Hello!")
request1.finish()
self.pump(0.1)
self.assertEqual(channel1.code, 200, channel1.result["body"])
self.assertEqual(channel1.result["body"], b"Hello!")
# Now respond to the second with the same content.
request2.setResponseCode(200)
request2.responseHeaders.setRawHeaders(b"Content-Type", [b"text/plain"])
request2.write(b"Hello!")
request2.finish()
self.pump(0.1)
self.assertEqual(channel2.code, 200, channel2.result["body"])
self.assertEqual(channel2.result["body"], b"Hello!")
# We expect only one new file to have been persisted.
self.assertEqual(start_count + 1, self._count_remote_media())
def test_download_image_race(self):
"""Test that fetching remote *images* from two different processes at
the same time works.
This checks that races generating thumbnails are handled correctly.
"""
hs1 = self.make_worker_hs("synapse.app.generic_worker")
hs2 = self.make_worker_hs("synapse.app.generic_worker")
start_count = self._count_remote_thumbnails()
channel1, request1 = self._get_media_req(hs1, "example.com:443", "PIC1")
channel2, request2 = self._get_media_req(hs2, "example.com:443", "PIC1")
png_data = unhexlify(
b"89504e470d0a1a0a0000000d4948445200000001000000010806"
b"0000001f15c4890000000a49444154789c63000100000500010d"
b"0a2db40000000049454e44ae426082"
)
request1.setResponseCode(200)
request1.responseHeaders.setRawHeaders(b"Content-Type", [b"image/png"])
request1.write(png_data)
request1.finish()
self.pump(0.1)
self.assertEqual(channel1.code, 200, channel1.result["body"])
self.assertEqual(channel1.result["body"], png_data)
request2.setResponseCode(200)
request2.responseHeaders.setRawHeaders(b"Content-Type", [b"image/png"])
request2.write(png_data)
request2.finish()
self.pump(0.1)
self.assertEqual(channel2.code, 200, channel2.result["body"])
self.assertEqual(channel2.result["body"], png_data)
# We expect only three new thumbnails to have been persisted.
self.assertEqual(start_count + 3, self._count_remote_thumbnails())
def _count_remote_media(self) -> int:
"""Count the number of files in our remote media directory.
"""
path = os.path.join(
self.hs.get_media_repository().primary_base_path, "remote_content"
)
return sum(len(files) for _, _, files in os.walk(path))
def _count_remote_thumbnails(self) -> int:
"""Count the number of files in our remote thumbnails directory.
"""
path = os.path.join(
self.hs.get_media_repository().primary_base_path, "remote_thumbnail"
)
return sum(len(files) for _, _, files in os.walk(path))
def get_connection_factory():
# this needs to happen once, but not until we are ready to run the first test
global test_server_connection_factory
if test_server_connection_factory is None:
test_server_connection_factory = TestServerTLSConnectionFactory(
sanlist=[b"DNS:example.com"]
)
return test_server_connection_factory
def _build_test_server(connection_creator):
"""Construct a test server
This builds an HTTP channel, wrapped with a TLSMemoryBIOProtocol
Args:
connection_creator (IOpenSSLServerConnectionCreator): thing to build
SSL connections
sanlist (list[bytes]): list of the SAN entries for the cert returned
by the server
Returns:
TLSMemoryBIOProtocol
"""
server_factory = Factory.forProtocol(HTTPChannel)
# Request.finish expects the factory to have a 'log' method.
server_factory.log = _log_request
server_tls_factory = TLSMemoryBIOFactory(
connection_creator, isClient=False, wrappedFactory=server_factory
)
return server_tls_factory.buildProtocol(None)
def _log_request(request):
"""Implements Factory.log, which is expected by Request.finish"""
logger.info("Completed request %s", request)

2
tests/server.py
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@ -46,7 +46,7 @@ class FakeChannel:
site = attr.ib(type=Site)
_reactor = attr.ib()
result = attr.ib(default=attr.Factory(dict))
result = attr.ib(type=dict, default=attr.Factory(dict))
_producer = None
@property