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Merge pull request #1262 from tahoe-lafs/3935-happy-eyeballs

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MVP happy eyeballs for HTTP storage protocol

Fixes ticket:3935
Fixes ticket:3981
This commit is contained in:
Itamar Turner-Trauring 2023-03-21 12:51:37 -04:00 committed by GitHub
commit 559e2ecdab
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7 changed files with 403 additions and 42 deletions
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0
newsfragments/3935.minor Normal file
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5
src/allmydata/storage/http_client.py
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@ -311,9 +311,7 @@ class StorageClient(object):
@classmethod
def from_nurl(
cls,
nurl: DecodedURL,
reactor,
cls, nurl: DecodedURL, reactor, pool: Optional[HTTPConnectionPool] = None
) -> StorageClient:
"""
Create a ``StorageClient`` for the given NURL.
@ -322,6 +320,7 @@ class StorageClient(object):
assert nurl.scheme == "pb"
swissnum = nurl.path[0].encode("ascii")
certificate_hash = nurl.user.encode("ascii")
if pool is None:
pool = HTTPConnectionPool(reactor)
pool.maxPersistentPerHost = 20

98
src/allmydata/storage_client.py
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@ -33,8 +33,7 @@ Ported to Python 3.
from __future__ import annotations
from six import ensure_text
from typing import Union, Any
from typing import Union, Callable, Any, Optional
from os import urandom
import re
import time
@ -44,6 +43,7 @@ from configparser import NoSectionError
import attr
from hyperlink import DecodedURL
from twisted.web.client import HTTPConnectionPool
from zope.interface import (
Attribute,
Interface,
@ -83,7 +83,7 @@ from allmydata.util.observer import ObserverList
from allmydata.util.rrefutil import add_version_to_remote_reference
from allmydata.util.hashutil import permute_server_hash
from allmydata.util.dictutil import BytesKeyDict, UnicodeKeyDict
from allmydata.util.deferredutil import async_to_deferred
from allmydata.util.deferredutil import async_to_deferred, race
from allmydata.storage.http_client import (
StorageClient, StorageClientImmutables, StorageClientGeneral,
ClientException as HTTPClientException, StorageClientMutables,
@ -1019,6 +1019,36 @@ class NativeStorageServer(service.MultiService):
self._reconnector.reset()
@async_to_deferred
async def _pick_a_http_server(
reactor,
nurls: list[DecodedURL],
request: Callable[[Any, DecodedURL], defer.Deferred[Any]]
) -> Optional[DecodedURL]:
"""Pick the first server we successfully send a request to.
Fires with ``None`` if no server was found, or with the ``DecodedURL`` of
the first successfully-connected server.
"""
queries = race([
request(reactor, nurl).addCallback(lambda _, nurl=nurl: nurl)
for nurl in nurls
])
try:
_, nurl = await queries
return nurl
except Exception as e:
# Logging errors breaks a bunch of tests, and it's not a _bug_ to
# have a failed connection, it's often expected and transient. More
# of a warning, really?
log.msg(
"Failed to connect to a storage server advertised by NURL: {}".format(
e)
)
return None
@implementer(IServer)
class HTTPNativeStorageServer(service.MultiService):
"""
@ -1045,12 +1075,11 @@ class HTTPNativeStorageServer(service.MultiService):
self._short_description,
self._long_description
) = _parse_announcement(server_id, furl, announcement)
# TODO need some way to do equivalent of Happy Eyeballs for multiple NURLs?
# https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3935
nurl = DecodedURL.from_text(announcement[ANONYMOUS_STORAGE_NURLS][0])
self._istorage_server = _HTTPStorageServer.from_http_client(
StorageClient.from_nurl(nurl, reactor)
)
self._nurls = [
DecodedURL.from_text(u)
for u in announcement[ANONYMOUS_STORAGE_NURLS]
]
self._istorage_server = None
self._connection_status = connection_status.ConnectionStatus.unstarted()
self._version = None
@ -1167,7 +1196,46 @@ class HTTPNativeStorageServer(service.MultiService):
def try_to_connect(self):
self._connect()
def _connect(self):
@async_to_deferred
async def _connect(self):
if self._istorage_server is None:
# We haven't selected a server yet, so let's do so.
# TODO This is somewhat inefficient on startup: it takes two successful
# version() calls before we are live talking to a server, it could only
# be one. See https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3992
# TODO Another problem with this scheme is that while picking
# the HTTP server to talk to, we don't have connection status
# updates... https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3978
def request(reactor, nurl: DecodedURL):
# Since we're just using this one off to check if the NURL
# works, no need for persistent pool or other fanciness.
pool = HTTPConnectionPool(reactor, persistent=False)
pool.retryAutomatically = False
return StorageClientGeneral(
StorageClient.from_nurl(nurl, reactor, pool)
).get_version()
# LoopingCall.stop() doesn't cancel Deferreds, unfortunately:
# https://github.com/twisted/twisted/issues/11814 Thus we want
# store the Deferred so it gets cancelled.
picking = _pick_a_http_server(reactor, self._nurls, request)
self._connecting_deferred = picking
try:
nurl = await picking
finally:
self._connecting_deferred = None
if nurl is None:
# We failed to find a server to connect to. Perhaps the next
# iteration of the loop will succeed.
return
else:
self._istorage_server = _HTTPStorageServer.from_http_client(
StorageClient.from_nurl(nurl, reactor)
)
result = self._istorage_server.get_version()
def remove_connecting_deferred(result):
@ -1181,6 +1249,14 @@ class HTTPNativeStorageServer(service.MultiService):
self._failed_to_connect
)
# We don't want to do another iteration of the loop until this
# iteration has finished, so wait here:
try:
if self._connecting_deferred is not None:
await self._connecting_deferred
except Exception as e:
log.msg(f"Failed to connect to a HTTP storage server: {e}", level=log.CURIOUS)
def stopService(self):
if self._connecting_deferred is not None:
self._connecting_deferred.cancel()
@ -1354,7 +1430,7 @@ class _HTTPBucketWriter(object):
return self.finished
def _ignore_404(failure: Failure) -> Union[Failure, None]:
def _ignore_404(failure: Failure) -> Optional[Failure]:
"""
Useful for advise_corrupt_share(), since it swallows unknown share numbers
in Foolscap.

160
src/allmydata/test/test_deferredutil.py
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@ -1,23 +1,18 @@
"""
Tests for allmydata.util.deferredutil.
Ported to Python 3.
"""
from __future__ import unicode_literals
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from future.utils import PY2
if PY2:
from builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, list, object, range, str, max, min # noqa: F401
from __future__ import annotations
from twisted.trial import unittest
from twisted.internet import defer, reactor
from twisted.internet.defer import Deferred
from twisted.python.failure import Failure
from hypothesis.strategies import integers
from hypothesis import given
from allmydata.util import deferredutil
from allmydata.util.deferredutil import race, MultiFailure
class DeferredUtilTests(unittest.TestCase, deferredutil.WaitForDelayedCallsMixin):
@ -157,3 +152,148 @@ class AsyncToDeferred(unittest.TestCase):
result = f(1, 0)
self.assertIsInstance(self.failureResultOf(result).value, ZeroDivisionError)
def _setupRaceState(numDeferreds: int) -> tuple[list[int], list[Deferred[object]]]:
"""
Create a list of Deferreds and a corresponding list of integers
tracking how many times each Deferred has been cancelled. Without
additional steps the Deferreds will never fire.
"""
cancelledState = [0] * numDeferreds
ds: list[Deferred[object]] = []
for n in range(numDeferreds):
def cancel(d: Deferred, n: int = n) -> None:
cancelledState[n] += 1
ds.append(Deferred(canceller=cancel))
return cancelledState, ds
class RaceTests(unittest.SynchronousTestCase):
"""
Tests for L{race}.
"""
@given(
beforeWinner=integers(min_value=0, max_value=3),
afterWinner=integers(min_value=0, max_value=3),
)
def test_success(self, beforeWinner: int, afterWinner: int) -> None:
"""
When one of the L{Deferred}s passed to L{race} fires successfully,
the L{Deferred} return by L{race} fires with the index of that
L{Deferred} and its result and cancels the rest of the L{Deferred}s.
@param beforeWinner: A randomly selected number of Deferreds to
appear before the "winning" Deferred in the list passed in.
@param beforeWinner: A randomly selected number of Deferreds to
appear after the "winning" Deferred in the list passed in.
"""
cancelledState, ds = _setupRaceState(beforeWinner + 1 + afterWinner)
raceResult = race(ds)
expected = object()
ds[beforeWinner].callback(expected)
# The result should be the index and result of the only Deferred that
# fired.
self.assertEqual(
self.successResultOf(raceResult),
(beforeWinner, expected),
)
# All Deferreds except the winner should have been cancelled once.
expectedCancelledState = [1] * beforeWinner + [0] + [1] * afterWinner
self.assertEqual(
cancelledState,
expectedCancelledState,
)
@given(
beforeWinner=integers(min_value=0, max_value=3),
afterWinner=integers(min_value=0, max_value=3),
)
def test_failure(self, beforeWinner: int, afterWinner: int) -> None:
"""
When all of the L{Deferred}s passed to L{race} fire with failures,
the L{Deferred} return by L{race} fires with L{MultiFailure} wrapping
all of their failures.
@param beforeWinner: A randomly selected number of Deferreds to
appear before the "winning" Deferred in the list passed in.
@param beforeWinner: A randomly selected number of Deferreds to
appear after the "winning" Deferred in the list passed in.
"""
cancelledState, ds = _setupRaceState(beforeWinner + 1 + afterWinner)
failure = Failure(Exception("The test demands failures."))
raceResult = race(ds)
for d in ds:
d.errback(failure)
actualFailure = self.failureResultOf(raceResult, MultiFailure)
self.assertEqual(
actualFailure.value.failures,
[failure] * len(ds),
)
self.assertEqual(
cancelledState,
[0] * len(ds),
)
@given(
beforeWinner=integers(min_value=0, max_value=3),
afterWinner=integers(min_value=0, max_value=3),
)
def test_resultAfterCancel(self, beforeWinner: int, afterWinner: int) -> None:
"""
If one of the Deferreds fires after it was cancelled its result
goes nowhere. In particular, it does not cause any errors to be
logged.
"""
# Ensure we have a Deferred to win and at least one other Deferred
# that can ignore cancellation.
ds: list[Deferred[None]] = [
Deferred() for n in range(beforeWinner + 2 + afterWinner)
]
raceResult = race(ds)
ds[beforeWinner].callback(None)
ds[beforeWinner + 1].callback(None)
self.successResultOf(raceResult)
self.assertEqual(len(self.flushLoggedErrors()), 0)
def test_resultFromCancel(self) -> None:
"""
If one of the input Deferreds has a cancel function that fires it
with success, nothing bad happens.
"""
winner: Deferred[object] = Deferred()
ds: list[Deferred[object]] = [
winner,
Deferred(canceller=lambda d: d.callback(object())),
]
expected = object()
raceResult = race(ds)
winner.callback(expected)
self.assertEqual(self.successResultOf(raceResult), (0, expected))
@given(
numDeferreds=integers(min_value=1, max_value=3),
)
def test_cancel(self, numDeferreds: int) -> None:
"""
If the result of L{race} is cancelled then all of the L{Deferred}s
passed in are cancelled.
"""
cancelledState, ds = _setupRaceState(numDeferreds)
raceResult = race(ds)
raceResult.cancel()
self.assertEqual(cancelledState, [1] * numDeferreds)
self.failureResultOf(raceResult, MultiFailure)

75
src/allmydata/test/test_storage_client.py
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@ -1,22 +1,16 @@
"""
Ported from Python 3.
Tests for allmydata.storage_client.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals
from future.utils import PY2
if PY2:
from future.builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, list, object, range, str, max, min # noqa: F401
from six import ensure_text
from __future__ import annotations
from json import (
loads,
)
import hashlib
from typing import Union, Any, Optional
from hyperlink import DecodedURL
from fixtures import (
TempDir,
)
@ -60,6 +54,7 @@ from twisted.internet.defer import (
from twisted.python.filepath import (
FilePath,
)
from twisted.internet.task import Clock
from foolscap.api import (
Tub,
@ -94,7 +89,8 @@ from allmydata.storage_client import (
StorageFarmBroker,
_FoolscapStorage,
_NullStorage,
ANONYMOUS_STORAGE_NURLS
_pick_a_http_server,
ANONYMOUS_STORAGE_NURLS,
)
from ..storage.server import (
StorageServer,
@ -478,7 +474,7 @@ class StoragePluginWebPresence(AsyncTestCase):
# config validation policy).
"tub.port": tubport_endpoint,
"tub.location": tubport_location,
"web.port": ensure_text(webport_endpoint),
"web.port": str(webport_endpoint),
},
storage_plugin=self.storage_plugin,
basedir=self.basedir,
@ -781,3 +777,56 @@ storage:
StorageFarmBroker._should_we_use_http(node_config, announcement),
expected_http_usage
)
class PickHTTPServerTests(unittest.SynchronousTestCase):
"""Tests for ``_pick_a_http_server``."""
def pick_result(self, url_to_results: dict[DecodedURL, tuple[float, Union[Exception, Any]]]) -> Optional[DecodedURL]:
"""
Given mapping of URLs to (delay, result), return the URL of the
first selected server, or None.
"""
clock = Clock()
def request(reactor, url):
delay, value = url_to_results[url]
result = Deferred()
def add_result_value():
if isinstance(value, Exception):
result.errback(value)
else:
result.callback(value)
reactor.callLater(delay, add_result_value)
return result
d = _pick_a_http_server(clock, list(url_to_results.keys()), request)
for i in range(100):
clock.advance(0.1)
return self.successResultOf(d)
def test_first_successful_connect_is_picked(self):
"""
Given multiple good URLs, the first one that connects is chosen.
"""
earliest_url = DecodedURL.from_text("http://a")
latest_url = DecodedURL.from_text("http://b")
bad_url = DecodedURL.from_text("http://bad")
result = self.pick_result({
latest_url: (2, None),
earliest_url: (1, None),
bad_url: (0.5, RuntimeError()),
})
self.assertEqual(result, earliest_url)
def test_failures_are_turned_into_none(self):
"""
If the requests all fail, ``_pick_a_http_server`` returns ``None``.
"""
eventually_good_url = DecodedURL.from_text("http://good")
bad_url = DecodedURL.from_text("http://bad")
result = self.pick_result({
eventually_good_url: (1, ZeroDivisionError()),
bad_url: (0.1, RuntimeError())
})
self.assertEqual(result, None)

100
src/allmydata/util/deferredutil.py
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@ -1,15 +1,18 @@
"""
Utilities for working with Twisted Deferreds.
Ported to Python 3.
"""
from __future__ import annotations
import time
from functools import wraps
from typing import (
Callable,
Any,
Sequence,
TypeVar,
Optional,
)
from foolscap.api import eventually
@ -17,6 +20,7 @@ from eliot.twisted import (
inline_callbacks,
)
from twisted.internet import defer, reactor, error
from twisted.internet.defer import Deferred
from twisted.python.failure import Failure
from allmydata.util import log
@ -234,3 +238,95 @@ def async_to_deferred(f):
return defer.Deferred.fromCoroutine(f(*args, **kwargs))
return not_async
class MultiFailure(Exception):
"""
More than one failure occurred.
"""
def __init__(self, failures: Sequence[Failure]) -> None:
super(MultiFailure, self).__init__()
self.failures = failures
_T = TypeVar("_T")
# Eventually this should be in Twisted upstream:
# https://github.com/twisted/twisted/pull/11818
def race(ds: Sequence[Deferred[_T]]) -> Deferred[tuple[int, _T]]:
"""
Select the first available result from the sequence of Deferreds and
cancel the rest.
@return: A cancellable L{Deferred} that fires with the index and output of
the element of C{ds} to have a success result first, or that fires
with L{MultiFailure} holding a list of their failures if they all
fail.
"""
# Keep track of the Deferred for the action which completed first. When
# it completes, all of the other Deferreds will get cancelled but this one
# shouldn't be. Even though it "completed" it isn't really done - the
# caller will still be using it for something. If we cancelled it,
# cancellation could propagate down to them.
winner: Optional[Deferred] = None
# The cancellation function for the Deferred this function returns.
def cancel(result: Deferred) -> None:
# If it is cancelled then we cancel all of the Deferreds for the
# individual actions because there is no longer the possibility of
# delivering any of their results anywhere. We don't have to fire
# `result` because the Deferred will do that for us.
for d in to_cancel:
d.cancel()
# The Deferred that this function will return. It will fire with the
# index and output of the action that completes first, or None if all of
# the actions fail. If it is cancelled, all of the actions will be
# cancelled.
final_result: Deferred[tuple[int, _T]] = Deferred(canceller=cancel)
# A callback for an individual action.
def succeeded(this_output: _T, this_index: int) -> None:
# If it is the first action to succeed then it becomes the "winner",
# its index/output become the externally visible result, and the rest
# of the action Deferreds get cancelled. If it is not the first
# action to succeed (because some action did not support
# cancellation), just ignore the result. It is uncommon for this
# callback to be entered twice. The only way it can happen is if one
# of the input Deferreds has a cancellation function that fires the
# Deferred with a success result.
nonlocal winner
if winner is None:
# This is the first success. Act on it.
winner = to_cancel[this_index]
# Cancel the rest.
for d in to_cancel:
if d is not winner:
d.cancel()
# Fire our Deferred
final_result.callback((this_index, this_output))
# Keep track of how many actions have failed. If they all fail we need to
# deliver failure notification on our externally visible result.
failure_state = []
def failed(failure: Failure, this_index: int) -> None:
failure_state.append((this_index, failure))
if len(failure_state) == len(to_cancel):
# Every operation failed.
failure_state.sort()
failures = [f for (ignored, f) in failure_state]
final_result.errback(MultiFailure(failures))
# Copy the sequence of Deferreds so we know it doesn't get mutated out
# from under us.
to_cancel = list(ds)
for index, d in enumerate(ds):
# Propagate the position of this action as well as the argument to f
# to the success callback so we can cancel the right Deferreds and
# propagate the result outwards.
d.addCallbacks(succeeded, failed, callbackArgs=(index,), errbackArgs=(index,))
return final_result

3
tox.ini
View File

@ -10,6 +10,7 @@ python =
3.8: py38-coverage
3.9: py39-coverage
3.10: py310-coverage
3.11: py311-coverage
pypy-3.8: pypy38
pypy-3.9: pypy39
@ -17,7 +18,7 @@ python =
twisted = 1
[tox]
envlist = typechecks,codechecks,py{38,39,310}-{coverage},pypy27,pypy38,pypy39,integration
envlist = typechecks,codechecks,py{38,39,310,311}-{coverage},pypy27,pypy38,pypy39,integration
minversion = 2.4
[testenv]