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Zulip has had a small use of WebSockets (specifically, for the code path of sending messages, via the webapp only) since ~2013. We originally added this use of WebSockets in the hope that the latency benefits of doing so would allow us to avoid implementing a markdown local echo; they were not. Further, HTTP/2 may have eliminated the latency difference we hoped to exploit by using WebSockets in any case. While we’d originally imagined using WebSockets for other endpoints, there was never a good justification for moving more components to the WebSockets system. This WebSockets code path had a lot of downsides/complexity, including: * The messy hack involving constructing an emulated request object to hook into doing Django requests. * The `message_senders` queue processor system, which increases RAM needs and must be provisioned independently from the rest of the server). * A duplicate check_send_receive_time Nagios test specific to WebSockets. * The requirement for users to have their firewalls/NATs allow WebSocket connections, and a setting to disable them for networks where WebSockets don’t work. * Dependencies on the SockJS family of libraries, which has at times been poorly maintained, and periodically throws random JavaScript exceptions in our production environments without a deep enough traceback to effectively investigate. * A total of about 1600 lines of our code related to the feature. * Increased load on the Tornado system, especially around a Zulip server restart, and especially for large installations like zulipchat.com, resulting in extra delay before messages can be sent again. As detailed in https://github.com/zulip/zulip/pull/12862#issuecomment-536152397, it appears that removing WebSockets moderately increases the time it takes for the `send_message` API query to return from the server, but does not significantly change the time between when a message is sent and when it is received by clients. We don’t understand the reason for that change (suggesting the possibility of a measurement error), and even if it is a real change, we consider that potential small latency regression to be acceptable. If we later want WebSockets, we’ll likely want to just use Django Channels. Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
42 lines
1.6 KiB
Python
42 lines
1.6 KiB
Python
from argparse import ArgumentParser
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from typing import Any
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from django.core.management import CommandError
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from django.core.management.base import BaseCommand
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from zerver.lib.queue import SimpleQueueClient
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from zerver.worker.queue_processors import get_active_worker_queues
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class Command(BaseCommand):
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def add_arguments(self, parser: ArgumentParser) -> None:
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parser.add_argument(dest="queue_name", type=str, nargs='?',
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help="queue to purge", default=None)
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parser.add_argument('--all', dest="all", action="store_true",
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default=False, help="purge all queues")
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help = "Discards all messages from the given queue"
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def handle(self, *args: Any, **options: str) -> None:
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def purge_queue(queue_name: str) -> None:
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queue = SimpleQueueClient()
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queue.ensure_queue(queue_name, lambda: None)
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queue.channel.queue_purge(queue_name)
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if options['all']:
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for queue_name in get_active_worker_queues():
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purge_queue(queue_name)
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print("All queues purged")
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elif not options['queue_name']:
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raise CommandError("Missing queue_name argument!")
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else:
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queue_name = options['queue_name']
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if not (queue_name in get_active_worker_queues() or
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queue_name.startswith("notify_tornado")):
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raise CommandError("Unknown queue %s" % (queue_name,))
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print("Purging queue %s" % (queue_name,))
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purge_queue(queue_name)
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print("Done")
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