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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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| .. | ||
| analytics.md | ||
| api-release-checklist.md | ||
| billing.md | ||
| caching.md | ||
| client.md | ||
| conversion.md | ||
| custom-apps.md | ||
| dependencies.md | ||
| django-upgrades.md | ||
| email.md | ||
| emoji.md | ||
| events-system.md | ||
| full-text-search.md | ||
| hashchange-system.md | ||
| hotspots.md | ||
| html-css.md | ||
| index.rst | ||
| input-pills.md | ||
| logging.md | ||
| management-commands.md | ||
| markdown.md | ||
| pointer.md | ||
| presence.md | ||
| queuing.md | ||
| realms.md | ||
| release-checklist.md | ||
| schema-migrations.md | ||
| sending-messages.md | ||
| settings.md | ||
| thumbnailing.md | ||
| typing-indicators.md | ||
| unread_messages.md | ||
| users.md | ||
| widgets.md | ||