def install_dns_limiter(reactor, max_dns_requests_in_flight=100):
"""Replaces the resolver with one that limits the number of in flight DNS
requests.
This is to workaround https://twistedmatrix.com/trac/ticket/9620, where we
can run out of file descriptors and infinite loop if we attempt to do too
many DNS queries at once
"""
new_resolver = _LimitedHostnameResolver(reactor.nameResolver,
max_dns_requests_in_flight)
reactor.installNameResolver(new_resolver)
def install_dns_limiter(reactor, max_dns_requests_in_flight=100):
"""Replaces the resolver with one that limits the number of in flight DNS
requests.
This is to workaround https://twistedmatrix.com/trac/ticket/9620, where we
can run out of file descriptors and infinite loop if we attempt to do too
many DNS queries at once
"""
new_resolver = _LimitedHostnameResolver(
reactor.nameResolver, max_dns_requests_in_flight,
)
reactor.installNameResolver(new_resolver)
def install_dns_limiter(reactor, max_dns_requests_in_flight=100):
"""Replaces the resolver with one that limits the number of in flight DNS
requests.
This is to workaround https://twistedmatrix.com/trac/ticket/9620, where we
can run out of file descriptors and infinite loop if we attempt to do too
many DNS queries at once
XXX: I'm confused by this. reactor.nameResolver does not use twisted.names unless
you explicitly install twisted.names as the resolver; rather it uses a GAIResolver
backed by the reactor's default threadpool (which is limited to 10 threads). So
(a) I don't understand why twisted ticket 9620 is relevant, and (b) I don't
understand why we would run out of FDs if we did too many lookups at once.
-- richvdh 2020/08/29
"""
new_resolver = _LimitedHostnameResolver(reactor.nameResolver,
max_dns_requests_in_flight)
reactor.installNameResolver(new_resolver)
async def start(hs: "HomeServer"):
"""
Start a Synapse server or worker.
Should be called once the reactor is running.
Will start the main HTTP listeners and do some other startup tasks, and then
notify systemd.
Args:
hs: homeserver instance
"""
reactor = hs.get_reactor()
# We want to use a separate thread pool for the resolver so that large
# numbers of DNS requests don't starve out other users of the threadpool.
resolver_threadpool = ThreadPool(name="gai_resolver")
resolver_threadpool.start()
reactor.addSystemEventTrigger("during", "shutdown",
resolver_threadpool.stop)
reactor.installNameResolver(
GAIResolver(reactor, getThreadPool=lambda: resolver_threadpool))
# Register the threadpools with our metrics.
register_threadpool("default", reactor.getThreadPool())
register_threadpool("gai_resolver", resolver_threadpool)
# Set up the SIGHUP machinery.
if hasattr(signal, "SIGHUP"):
@wrap_as_background_process("sighup")
def handle_sighup(*args, **kwargs):
# Tell systemd our state, if we're using it. This will silently fail if
# we're not using systemd.
sdnotify(b"RELOADING=1")
for i, args, kwargs in _sighup_callbacks:
i(*args, **kwargs)
sdnotify(b"READY=1")
# We defer running the sighup handlers until next reactor tick. This
# is so that we're in a sane state, e.g. flushing the logs may fail
# if the sighup happens in the middle of writing a log entry.
def run_sighup(*args, **kwargs):
# `callFromThread` should be "signal safe" as well as thread
# safe.
reactor.callFromThread(handle_sighup, *args, **kwargs)
signal.signal(signal.SIGHUP, run_sighup)
register_sighup(refresh_certificate, hs)
# Load the certificate from disk.
refresh_certificate(hs)
# Start the tracer
synapse.logging.opentracing.init_tracer(
hs) # type: ignore[attr-defined] # noqa
# Instantiate the modules so they can register their web resources to the module API
# before we start the listeners.
module_api = hs.get_module_api()
for module, config in hs.config.modules.loaded_modules:
module(config=config, api=module_api)
load_legacy_spam_checkers(hs)
load_legacy_third_party_event_rules(hs)
load_legacy_presence_router(hs)
load_legacy_password_auth_providers(hs)
# If we've configured an expiry time for caches, start the background job now.
setup_expire_lru_cache_entries(hs)
# It is now safe to start your Synapse.
hs.start_listening()
hs.get_datastore().db_pool.start_profiling()
hs.get_pusherpool().start()
# Log when we start the shut down process.
hs.get_reactor().addSystemEventTrigger("before", "shutdown", logger.info,
"Shutting down...")
setup_sentry(hs)
setup_sdnotify(hs)
# If background tasks are running on the main process, start collecting the
# phone home stats.
if hs.config.worker.run_background_tasks:
start_phone_stats_home(hs)
# We now freeze all allocated objects in the hopes that (almost)
# everything currently allocated are things that will be used for the
# rest of time. Doing so means less work each GC (hopefully).
#
# This only works on Python 3.7
if platform.python_implementation() == "CPython" and sys.version_info >= (
3, 7):
gc.collect()
gc.freeze()
# Speed up shutdowns by freezing all allocated objects. This moves everything
# into the permanent generation and excludes them from the final GC.
# Unfortunately only works on Python 3.7
if platform.python_implementation() == "CPython" and sys.version_info >= (
3, 7):
atexit.register(gc.freeze)