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perf: Attempt to prevent people joining known busted rooms #1503

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nex commented 2026-03-07 17:03:54 +00:00
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As people keep setting up a server and immediately start trying to join rooms that have caused performance issues for even some of the beefiest servers in the network, this PR introduces a more drastic measure to prevent people footgunning - a list of room IDs are now hardcoded to be blocked, which prevents even admins joining them, unless a config option is enabled.

This is necessary since people keep trying to join, for example, the Matrix Community space, and being unable to do so, or being able to do so, but later having their machines absolutely crushed trying to resolve the room's state some time later (see: pretty much everyone on the maintainer team, federated.nexus, even some big name public deployments have recently started banning this room). Once joined, leaving itself is a difficult process, and simply participating in the room is enough to cause performance issues, which is terrible for anyone who is just getting started.

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As people keep setting up a server and immediately start trying to join rooms that have caused performance issues for even some of the beefiest servers in the network, this PR introduces a more drastic measure to prevent people footgunning - a list of room IDs are now hardcoded to be blocked, which prevents even admins joining them, unless a config option is enabled. This is necessary since people keep trying to join, for example, the Matrix Community space, and being unable to do so, or being able to do so, but later having their machines absolutely crushed trying to resolve the room's state some time later (see: pretty much everyone on the maintainer team, federated.nexus, even some big name public deployments have recently started banning this room). Once joined, leaving itself is a difficult process, and simply participating in the room is enough to cause performance issues, which is *terrible* for anyone who is just getting started. <!-- Example: This pull request allows us to warp through time and space ten times faster than before by double-inverting the warp drive with hyperheated jump fluid, both making the drive faster and more efficient. This resolves the common issue where we have to wait more than 10 milliseconds to engage, use, and disengage the warp drive when travelling between galaxies. --> <!-- Closes: #... --> <!-- Fixes: #... --> <!-- Uncomment the above line(s) if your pull request fixes an issue or closes another pull request by superseding it. Replace `#...` with the issue/pr number, such as `#123`. --> **Pull request checklist:** <!-- You need to complete these before your PR can be considered. 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perf: Attempt to prevent people joining known busted rooms
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ginger reviewed 2026-03-07 17:05:27 +00:00
src/api/client/membership/mod.rs
@ -79,0 +87,4 @@
if !services.config.allow_joining_broken_rooms
&& BROKEN_ROOM_IDS.contains(&room_id.as_str())
{
return Err!(Request(Forbidden("This room is too complex.")));
ginger commented 2026-03-07 17:05:27 +00:00
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we may want to add a new section to the FAQ and have this error message link to it

we may want to add a new section to the FAQ and have this error message link to it
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nex added this to the next milestone 2026-03-07 17:07:10 +00:00
gamesguru reviewed 2026-03-08 03:37:59 +00:00
conduwuit-example.toml
@ -1522,0 +1534,4 @@
# forgo your right to complain about any slowdowns or inflated resource
# usage you encounter.
#
#allow_joining_broken_rooms = false
gamesguru commented 2026-03-08 03:37:59 +00:00
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couldn't it be better if admins could tweak the list? removing or adding individual rooms? We just gave them the default list as guidance.

couldn't it be better if admins could tweak the list? removing or adding individual rooms? We just gave them the default list as guidance.
nex commented 2026-03-08 03:43:02 +00:00
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!admin rooms moderation ban-room exists for user-configurable room bans; this is merely meant to provide a "default" set that prevents new users joining rooms that will just destroy their server while they're none the wiser.

`!admin rooms moderation ban-room` exists for user-configurable room bans; this is merely meant to provide a "default" set that prevents new users joining rooms that will just destroy their server while they're none the wiser.
gamesguru commented 2026-03-08 04:02:55 +00:00
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as in brick their server? or just require they evict a user in a race condition?

i agree there is overlap between the functions ban-room and the proposed room filter list. But unless there's a pattern of complete bricking, i'm against taking control away from admins completely. If they want to erase or comment out our recommendations, they will learn about race conditions and log spam.

I saw a similar thing indented deep in the code, a hard-coded rule. We should probably find out why these rooms break. Like if this room breaks because it's v5, we can adjust our interface in general for all room v5s. If it's just a bad room, we can add it to the proposed list. I am not sure we should be hard-coding edge cases throughout the production code, I would think it's better to leave them configurable.

...
		.ruma_route(&client::get_hierarchy_route)
		.ruma_route(&client::get_mutual_rooms_route)
		.ruma_route(&client::get_room_summary)
		.route(
			"/_matrix/client/unstable/im.nheko.summary/rooms/{room_id_or_alias}/summary",
			get(client::get_room_summary_legacy)
		)
		.ruma_route(&client::get_suspended_status)
		.ruma_route(&client::put_suspended_status)
		.ruma_route(&client::well_known_support)
...
as in brick their server? or just require they evict a user in a race condition? i agree there is overlap between the functions `ban-room` and the proposed room filter list. But unless there's a pattern of complete bricking, i'm against taking control away from admins completely. If they want to erase or comment out our recommendations, they will learn about race conditions and log spam. I saw a similar thing indented deep in the code, a hard-coded rule. We should probably find out why these rooms break. Like if this room breaks because it's v5, we can adjust our interface in general for all room v5s. If it's just a bad room, we can add it to the proposed list. I am not sure we should be hard-coding edge cases throughout the production code, I would think it's better to leave them configurable. ```rust ... .ruma_route(&client::get_hierarchy_route) .ruma_route(&client::get_mutual_rooms_route) .ruma_route(&client::get_room_summary) .route( "/_matrix/client/unstable/im.nheko.summary/rooms/{room_id_or_alias}/summary", get(client::get_room_summary_legacy) ) .ruma_route(&client::get_suspended_status) .ruma_route(&client::put_suspended_status) .ruma_route(&client::well_known_support) ... ```
gamesguru commented 2026-03-08 04:05:04 +00:00
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perhaps we could even just combine the two lists before even feeding it to the server, and treat ban/disable as the same

perhaps we could even just combine the two lists before even feeding it to the server, and treat ban/disable as the same
nex commented 2026-03-08 04:15:44 +00:00
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as in brick their server?

Pretty much.

i'm against taking control away from admins completely

I'm not sure what control this takes away? It simply prevents people joining a room without realising it will blow up their server. It can be turned on and off at will, and is independent from the runtime-configured bans, which are typically for a different purpose.

they will learn about race conditions and log spam.

The problem is this is the current system and it is resulting in almost daily people coming into our main room and complaining of slow joins / slow server / high CPU & RAM usage / insane disk usage inflation. We clearly need something to prevent people who are uneducated on the rooms they're joining from blowing up their server and not knowing until it's too late.

We should probably find out why these rooms break

It's because of state resets and/or insanely deep auth chains

Like if this room breaks because it's v5, we can adjust our interface in general for all room v5s.

We can't blanket affect like this - some v5 rooms (for example) are perfectly fine, whereas some are practically unusable. There's no one-size-fits-all :(

I am not sure we should be hard-coding edge cases throughout the production code

This is basically a last-resort. I don't want to do this either but I'm not seeing another option.

I would think it's better to leave them configurable.

I still don't understand this - you can manually ban and unban rooms with the relevant room moderation commands, that is configuration. Why would you add to the hardcoded list if you can just... use the admin command for the same effect?

> as in brick their server? Pretty much. > i'm against taking control away from admins completely I'm not sure what control this takes away? It simply prevents people joining a room without realising it will blow up their server. It can be turned on and off at will, and is independent from the runtime-configured bans, which are typically for a different purpose. > they will learn about race conditions and log spam. The problem is this is the current system and it is resulting in almost daily people coming into our main room and complaining of slow joins / slow server / high CPU & RAM usage / insane disk usage inflation. We clearly need something to prevent people who are uneducated on the rooms they're joining from blowing up their server and not knowing until it's too late. > We should probably find out why these rooms break It's because of state resets and/or insanely deep auth chains > Like if this room breaks because it's v5, we can adjust our interface in general for all room v5s. We can't blanket affect like this - some v5 rooms (for example) are perfectly fine, whereas some are practically unusable. There's no one-size-fits-all :( > I am not sure we should be hard-coding edge cases throughout the production code This is basically a last-resort. I don't want to do this either but I'm not seeing another option. > I would think it's better to leave them configurable. I still don't understand this - you can manually ban and unban rooms with the relevant room moderation commands, that *is* configuration. Why would you add to the hardcoded list if you can just... use the admin command for the same effect?
gamesguru reviewed 2026-03-08 03:38:11 +00:00
src/api/client/membership/mod.rs
@ -61,0 +67,4 @@
"!MBrxZRUoApYYjmyion:t2bot.io", // Old t2bot room - insane auth chain depths
"izahlpcyIDeymNjiOd:matrix.debian.social", // #debian-next:matrix.debian.social
"!mefQhZzgTaxNCNzAeK:kde.org", // KDE user help
"!OTxETzuhBDbnPqBqbP:kde.org", // KDE space
gamesguru commented 2026-03-08 03:38:11 +00:00
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oh hell yeah homie, i'm gonna join them all on my nightly account 🙌 LFG keep it maintained

oh hell yeah homie, i'm gonna join them all on my nightly account 🙌 LFG keep it maintained
gamesguru requested changes 2026-03-08 04:12:47 +00:00
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Please avoid hard-coding configuration values in production rust code. Brainstorm an approach which uses dynamic configuration if possible.

Please avoid hard-coding configuration values in production rust code. Brainstorm an approach which uses dynamic configuration if possible.
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