Application Service support tracking

[johannescpk]

The matrix-sdk-appservice crate should be considered experimental until this issue gets closed

Docs: https://matrix-org.github.io/matrix-rust-sdk/matrix_sdk_appservice/index.html

Todo

Bugs

• regex matching on registration namespaces chokes on escape sequences which makes it incompatible to how synapse handles it (e.g. '@uwu:owo\.tld')
• Running the appservice on a sub-path will not work correctly as ruma only parses URLs correctly that start with /_matrix as root (appservice: Support appservice located on sub path #304)
• register not properly working (appservice: Add warp support #254)
• Registering scope / for the fallback routes breaks consumer routes that are added after adding actix_service (appservice: Add warp support #254)
• if let Ok(client) = self.appservice.client(None).await {}; in EventHandler doesn't seem to work (appservice: Add warp support #254)

Hard

• Correctly recognize room membership based on namespaces (Update membership state of client user based on state events #507, refactor(appservice): Better virtual client sync #710, Appservice virt member test #747)
• Transaction tokens must be handled differently than the sync response token. (WIP: Make sure that we don't handle the transaction ID as a batch_token in appservices #853)
• Properly sync room state
  • Encountering a room the first time when processing a transaction should block further transaction processing and sync the state events for the room first. PR: appservice: Sync room state #303
• E2EE
  • Blocked by waiting for the implementation work around MSC3202. There are workarounds but the added complexity just isn't worth. Ready to be picked up: MSC3202: Encrypted appservices matrix-spec-proposals#3202 (comment)

Medium

• Expose user/room queries from the homeserver (https://matrix.org/docs/spec/application_service/r0.1.2#querying)
• Persist info about registered virtual users in the arbitrary SDK storage (Add custom storage #315)
• Basic test that checks whether ClientConfig & RequestConfig are correctly used
• Singleton for Appservice::client() (appservice: Add client_with_config singleton #249)
• Expose ClientConfig (appservice: Add client_with_config singleton #249)
• Add warp support (appservice: Add warp support #254)
  • Fully working support is blocked behind Expose tracing/log feature seanmonstar/warp#861, workaround is
    [patch.crates-io] warp = { version = "0.3", git = "https://github.com/johannescpk/warp", rev = "4ead0f", default-features = false, features = ["multipart", "websocket"] }
• Refactor actix example to use ? instead of unwrap

Easy

• Don't process transactions twice (Don't process the same transaction twice #560)
• Proper re-export and usage of ruma appservice api instead of hidden/inlined re-export (related: The SDK should use reexported types directly  #152)
  • Using re-exported ruma from a consumer doesn't completely work since it breaks the EventContent macro
• Switch warp dependency to crates.io version, blocked behind new warp release (after 0.3.1)
• docs: Explain that incoming transactions are handled by the main user client (appservice: Sync room state #303)
• Allow to drop or re-initialize cached singleton clients. Done via virtual_users returning the dashmap.
• Mention in the docs that the appservice is basically a wrapper around the sdk Client
• Remove outdated serde_yaml dependency from matrix-sdk crate
• Fix typo: try_into_http_request_with_identy_assertion -> try_into_http_request_with_identity_assertion :D
• Rename client_with_localpart to client_with_identity_assertion (appservice: Refactor API #231)
• Move get_host_and_port_from_registration into AppserviceRegistration::get_host_and_port (appservice: Refactor API #231)
• Check if it makes sense to introduce an InnerAppservice for Arc-purposes, or single Arcs for member fields (from feat: appservice #204 (comment))
• Initial version (feat: appservice #204)

Refactoring

• matrix_sdk_test: use SyncStateEvent::into_full_event instead of value_with_room_id
• Try intermediate conversion from http::Request instead (see appservice: Add warp support #254 (comment))
• Consider renaming Appservice to AppService (appservice: Rename Appservice to AppService #272)
• localpart-unwrap in Appservice::client and Appservice::client_with_config should be deduplicated and re-use get_cached_client instead, but was hitting some Send + Sync roadblock
• Using appservice in the actix examples probably wants a mutex instead of cloning, or maybe allow &mut self event handler methods
• Make localpart in client_with_config() a non-Option, since the main appservice user config can't get overwritten anyway

Optional / Nice to have

• Consider removing actix (appservice: Drop actix #290)
  • Reasoning: actix does a rather specific tokio runtime setup that leads to being able to easily block threads
• Think about appservice-FFI scenarios: would spawning the webserver in a thread already help? how to sanely FFI events / event handler?
• Support hyper: maybe merge in from matrix-appservice-rs? /cc @lieuwex
  • hyper is supported by using the warp filter as tower service
• Consider supporting constructing clients based on server_name & well-known
  • Related PR that introduces well-known support in the Client: Make client use .well-known redirects #233

Constant effort

• Tracing
• Test-Coverage

Other Application Service Implementations

(todo: feature matrix table?)

• https://github.com/matrix-org/matrix-appservice-node (JS, No E2EE OOTB)
• https://github.com/turt2live/matrix-bot-sdk (JS, Basic E2EE Support (Add basic encryption support for simple bots turt2live/matrix-bot-sdk#142))
• https://github.com/tulir/mautrix-go (Go, No E2EE OOTB)
  • https://github.com/tulir/mautrix-whatsapp (Go, E2EE OOTB)
• https://github.com/tulir/mautrix-python (Python, E2EE OOTB)
• https://github.com/lieuwex/matrix-appservice-rs (Rust, Standalone Client, No E2EE OOTB)

Bridge projects

• https://github.com/matrix-org/matrix-appservice-bridge (JS, Based on matrix-appservice and matrix-js-sdk)
• https://github.com/Sorunome/mx-puppet-bridge (JS, Based on matrix-bot-sdk)
• https://github.com/matrix-hacks/matrix-puppet-bridge (JS, Based on matrix-appservice-bridge)
• https://github.com/tulir/mautrix-python (Python)

Related projects

• Rust: https://github.com/matrix-org/matrix-ircd creates a matrix client per IRC user connection

[MTRNord]

Additional to the membership Bug is that invites only go to the EventHandler::on_room_member handler when they come in via the invite branch of the timeline (See:

matrix-rust-sdk/matrix_sdk/src/event_handler/mod.rs

Line 155 in 3c72304

AnySyncStateEvent::RoomMember(e) => self.on_room_member(room, e).await,

which gets called by

matrix-rust-sdk/matrix_sdk/src/event_handler/mod.rs

Lines 121 to 125 in 3c72304

	for event in
	room_info.timeline.events.iter().filter_map(|e| e.event.deserialize().ok())
	{
	self.handle_timeline_event(room.clone(), &event).await;
	}

which then gets called by

matrix-rust-sdk/matrix_sdk/src/client.rs

Line 651 in ee40d91

handler.handle_sync(&sync_response).await;

which however gets the wrong timelines from and has a joined instead of an Invite room that gets passed from https://github.com/matrix-org/matrix-rust-sdk/blob/master/matrix_sdk_base/src/client.rs#L886-L905 ).

This doesnt seem to be an easy fix as currently a) all appservice Events come via the join Part (due to ruma) and b) the Event handler Part where this gets relayed is struct typed. So the joined room struct cant be passed along to make this work from the join Part.

Using the following code I wasnt getting any member events whatsoever.

async fn on_room_member(&self, room: Room, event: &SyncStateEvent<MemberEventContent>) {
        if !&event.state_key.contains("@server_stats:nordgedanken.dev") {
            return;
        }
        info!("Got invite");

        if let MembershipState::Invite = event.content.membership {
            let client = self.appservice.client(Some("server_stats")).await;
            client.join_room_by_id(room.room_id()).await.unwrap();
            VoyagerBot::set_direct(client, room.clone(), event).await;
            info!("Successfully joined room {}", room.room_id());
        };
    }

I am running on MTRNord@bf59b65 currently

[johannescpk]

@MTRNord This should be fixed in #254 which also includes a bugfix due to improved test coverage. The issue being that identity assertion and auth forcing didn't work as expected any longer.

[johannescpk]

@MTRNord Also, about invite vs join events, please see https://docs.ruma.io/ruma/api/appservice/event/push_events/v1/struct.IncomingRequest.html#method.try_into_sync_response for the rationale. Added that text to the set_event_handler docs as well now. Hope that makes sense. If you have different ideas about it, please let me know.

[agraven]

I think item 4 in "Nice to have" can be checked since the linked PR has been merged

[johannescpk]

@agraven Clarified that item's description. The linked PR was only about introducing it on the Client, I think it needs more work to support it in the appservice crate

[Hywan]

I'm closing this issue since #2509 has removed matrix-sdk-appservice.