TARDIS - Time Agnostic Room DAG Inspection Service

TARDIS is a time-travelling debugger for Matrix room DAGs, which reads a plaintext file to graphically visualise a room using d3-dag for debugging purposes.

The original intention was to add it as a RightPanel widget to Element (particularly in p2p mode) to help figure out what's gone wrong if your P2P node goes weird. The current intention is to use it to explore the shape of public room DAGs to design better APIs for P2P federation.

It's effectively the real-life version of the 2014-vintage D3 "how matrix works" animation from the frontpage of Matrix.org.

Currently very experimental and PoC.

Generates stuff like this:

To use:

Requires node 20+

yarn install
yarn run start

or:

docker build -t tardis .
docker run --rm -p 5173:5173 tardis

Then provide a new-line delimited JSON file which contains events to render in the full federation format (with prev_events, etc). To get such a file for Synapse installations on Postgres, run the following (assuming matrix is the name of your DB):

$ psql matrix
matrix=> \t
Tuples only is on.
matrix=> \o the-file.ndjson
matrix=> select jsonb_insert(json::JSONB, '{event_id}', ('"' || event_id || '"')::JSONB) from event_json where event_id in 
    (select event_id from events where
        room_id='!THE_ROOM_ID' and
        stream_ordering < (select stream_ordering from events where event_id='$LATEST_EVENT_ID') and 
        stream_ordering > (select stream_ordering from events where event_id='$EARLIEST_EVENT_ID')
        order by stream_ordering asc
    );

You can drop the stream_ordering clauses if the room is small and you want to see the entire thing. The file created by these commands can be dropped as-is into TARDIS.

Event ID generation

Sometimes we want to create mock scenarios which don't exist in databases. We use placeholder event IDs in this case. However, state resolution demands that they are actual event IDs. Tardis uses the same code paths as Dendrite (via wasm) to generate the correct event IDs. To build the wasm, you need tinygo installed and then:

GOOS=js GOARCH=wasm tinygo build -o ./public/gmsl.wasm --no-debug ./cmd/wasm/main.go

A working version is already supplied with this repository.