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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> |
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| .. | ||
| third | ||
| __init__.py | ||
| build-pgroonga | ||
| certbot-maybe-renew | ||
| check-upstart | ||
| clean_emoji_cache.py | ||
| clean_node_cache.py | ||
| clean_venv_cache.py | ||
| clean-unused-caches | ||
| create-production-venv | ||
| create-thumbor-venv | ||
| email-mirror-postfix | ||
| hash_reqs.py | ||
| install | ||
| install-node | ||
| node_cache.py | ||
| pythonrc.py | ||
| queue_workers.py | ||
| setup_path_on_import.py | ||
| setup_venv.py | ||
| setup-apt-repo | ||
| setup-apt-repo-debathena | ||
| setup-yum-repo | ||
| unpack-zulip | ||
| upgrade-zulip | ||
| upgrade-zulip-from-git | ||
| upgrade-zulip-stage-2 | ||
| zulip_tools.py | ||