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Taking FOSDEM online via Matrix

2021-01-04 — General — Matthew Hodgson
FOSDEM

Imagine you could physically step into your favourite FOSS projects’ chatrooms, mailing lists or forums and talk in person to other community members, contributors or committers? Imagine you could see project leads show off their latest work in front of a packed audience, and then chat and brainstorm with them afterwards (and maybe grab a beer)? Imagine, as a developer, you could suddenly meet a random subset of your users, to hear and understand their joys and woes in person?

This is FOSDEM, Europe’s largest Free and Open Source conference, where every year thousands of people (last year, ~8,500) take over the Solbosch campus of the Université Libre de Bruxelles in Belgium for a weekend and turn it into both a cathedral and bazaar for FOSS, with over 800+ talks organised over 50+ tracks, hundreds of exhibitor stands, and the whole campus generally exploding into a physical manifestation of the Internet. The event is completely non-commercial and volunteer run, and is a truly unique and powerful (if slightly overwhelming!) experience to attend. Ever since we began Matrix in 2014, FOSDEM has been the focal point of our year as we’ve rushed to demonstrate our latest work and catch up with the wider community and sync with other projects.

This year, things are of course different. Thankfully FOSDEM 2020 snuck in a few weeks before the COVID-19 pandemic went viral, but for FOSDEM 2021 on Feb 6/7th the conference will inevitably happen online. When this was announced a few months back, we reached out to FOSDEM to see if we could help: we’d just had a lot of fun helping HOPE go online, and meanwhile a lot of the work that’s gone into Matrix and Element in 2020 has been around large-scale community collaboration due to COVID - particularly thanks to all the development driven by Element’s German Education work. Meanwhile, we obviously love FOSDEM and want it to succeed as much as possible online - and we want to attempt to solve the impossible paradox of faithfully capturing the atmosphere and community of an event which is “online communities, but in person!”... but online.

And so, over the last few weeks we’ve been hard at work with the FOSDEM team to figure out how to make this happen, and we wanted to give an update on how things are shaping up (and to hopefully reassure folks that things are on track, and that devrooms don’t need to make their own plans!).

Firstly, FOSDEM will have its own dedicated Matrix server at fosdem.org (hosted by EMS along with a tonne of Jitsi’s) acting as the social backbone for the event. Matrix is particularly well suited for this, because:

  • We’re an open standard comms protocol with an open network run under a non-profit foundation with loads of open source implementations (including the reference ones): folks can jump on board and participate via their own servers, clients, bridges, bots etc.
  • We provide official bridges through to IRC and XMPP (and most other chat systems), giving as much openness and choice as possible - if folks want to participate via Freenode and XMPP they can!
  • We’re built with large virtual communities in mind (e.g. Mozilla, KDE, Matrix itself) - for instance, we’ve worked a lot on moderation recently.
  • We’ve spent a lot of time improving widgets recently: these give the ability to embed arbitrary webapps into chatrooms - letting you add livestreams, video conferences, schedules, Q&A dashboards etc, augmenting a plain old chatroom into a much richer virtual experience that can hopefully capture the semantics and requirements of an event like FOSDEM.

We’re currently in the middle of setting up the server with a dedicated Element as the default client, but what we’re aiming for is:

  • Attendees can lurk as read-only guests in devrooms without needing to set up accounts (or they can of course use their existing Matrix/IRC/XMPP accounts)
  • Every devroom and track will have its own chatroom, where the audience can hang out and view the livestream of that particular devroom (using the normal FOSDEM video livestream system). There’ll also be a ‘backstage’ room per track for coordination between the devroom organisers and the speakers.
  • The talks themselves will be prerecorded to minimise risk of disaster, but each talk will have a question & answer session at the end which will be a live Jitsi broadcast from the speaker and a host who will relay questions from the devroom.
  • Each talk will have a dedicated room too, where after the official talk slot the audience can pop in and chat to the speaker more informally if they’re available (by text and/or by moderated jitsi). During the talk, this room will act as the ‘stage’ for the speaker & host to watch the livestream and conduct the question & answer session.
  • Every stand will also have its own chatroom and optional jitsi+livestream, as will BOFs or other adhoc events, so folks can get involved both by chat and video, to get as close to the real event as possible (although it’s unlikely we’ll capture the unique atmospheric conditions of K building, which may or may not be a bug ;)
  • There’ll also be a set of official support, social etc rooms - and of course folks can always create their own! Unfortunately folks will have to bring their own beer though :(
  • All of this will be orchestrated by a Matrix bot (which is rapidly taking shape over at https://github.com/matrix-org/conference-bot), responsible for orchestrating the hundreds of required rooms, setting up the right widgets and permissions, setting up bridges to IRC & XMPP, and keeping everything in sync with the official live FOSDEM schedule.

N.B. This is aspirational, and is all still subject to change, but that said - so far it’s all coming together pretty well, and hopefully our next update will be opening up the rooms and the server so that folks can get comfortable in advance of the event.

Huge thanks go to the FOSDEM team for trusting us to sort out the social/chat layer of FOSDEM 2021 - we will do everything we can to make it as successful and as inclusive as we possibly can! :)

P.S. We need help!

FOSDEM is only a handful of weeks away, and we have our work cut out to bring this all together in time. There are a few areas where we could really do with some help:

  • Folks on XMPP often complain that the Bifröst Matrix<->XMPP bridge doesn’t support MAMs - meaning that if XMPP users lose connection, they lose scrollback. We’re not going to have time to fix this ourselves in time, so this would be a great time for XMPP folks who grok xmpp.js to come get involved and help to ensure the best possible XMPP experience! (Similarly on other bifrost shortcomings).
  • It’d be really nice to be able to render nice schedule widgets for each devroom, and embed the overall schedule in the support rooms etc. The current HTML schedules at https://fosdem.org/2021/schedule/day/saturday/ and (say) https://fosdem.org/2021/schedule/room/vcollab/ don’t exactly fit - if someone could write a thing which renders them at (say) 2:5 aspect ratio so they can fit nicely down the side of a chatroom then that could be awesome!
  • While we’ll bridge all the official rooms over to Freenode, it’d be even nicer if people could just hop straight into any room on the FOSDEM server (or beyond) via IRC - effectively exposing the whole thing as an IRC network for those who prefer IRC. We have a project to do this: matrix-ircd, but it almost certainly needs more love and polish before it could be used for something as big as this. If you like Rust and know Matrix, please jump in and get involved!
  • If you just want to follow along or help out, then we’ve created a general room for discussion over at #fosdem-matrix:fosdem.org. It’d be awesome to have as many useful bots & widgets as possible to help things along.

The Matrix Holiday Special 2020

2020-12-25 — General — Matthew Hodgson

Hi all,

Over the years it’s become a tradition to write an end-of-year wrap-up on Christmas Eve, reviewing all the things the core Matrix team has been up over the year, and looking forwards to the next (e.g. here’s last year’s edition). These days there’s so much going on in Matrix it’s impossible to cover it all (and besides, we now have This Week In Matrix and better blogging in general to cover events as they happen). So here’s a quick overview of the highlights:

Looking back at our plans for 2020 in last year’s wrap-up, amazingly it seems we pretty much achieved what we set out to do. Going through the bulletpoints in order:

  • We turned on End-to-end Encryption by default.
  • We have a dedicated team making major improvements to First-Time User Experience in Element (as of the last few months; hopefully you’ve been noticing the improvements!)
  • RiotX became Element Android and shipped.
  • Communities have been completely reinvented as Spaces (MSC1772) and while in alpha currently, they should ship in Jan.
  • Synapse scalability is fixed: we now shard horizontally by event - and Synapse is now pretty much entirely async/await!
  • Dendrite Beta shipped, as did the initial P2P Matrix experiments, which have subsequently continued to evolve significantly (although we haven’t implemented MSC1228 or MSC2787 portable accounts yet). Check out the Dendrite end-of-year update for more.
  • MLS experiments are in full swing - we got the first MLS messages passing over Matrix a few days ago, and Decentralised MLS work is back on the menu after an initial sprint in May.
  • There’s been a valiant mission to improve Bridge UX in the form of MSC2346 and its implementations in Element Web, although this has ended up failing to get to the top of the todo list (sorry Half-Shot! :/)
  • Spec progress has improved somewhat, and we are very excited to have welcomed Will Bamberg (formerly MDN) to support the spec from a professional tech writer perspective, with the all-new engine landing any day now! We’re still experimenting with ways to ensure the spec gets enough time allocated to keep up with the backlog, however - particularly community contributions.
  • ...and in terms of Abuse/Reputation - we properly kicked off our anti-abuse work and launched a first PoC implementation in the depths of Cerulean last week.

Perhaps more interesting is the stuff we didn’t predict (or at least didn’t want to pre-announce ;) for 2020:

  • Riot, Modular and New Vector got unified at last behind a single name: Element; hopefully the shock has worn off by now :)
  • Mozilla joined Matrix in force, turning off Moznet IRC in favour of going full Matrix.
  • We welcomed Gitter into the heart of the Matrix ecosystem (with Element acquiring Gitter from Gitlab in order to ensure Gitter’s Matrix integration acts as a reference for integrating future chat silos into Matrix) - with native Matrix support in Gitter going live shortly afterwards.
  • Automattic launched itself into the Matrix ecosystem with an investment in Element, and since then we’ve been working on getting Matrix better integrated and available to them (although all of Element’s Matrix-for-governments activity has ended up delaying this a bit). If you want to work for Automattic on integrating Matrix, they’re hiring!
  • We previewed Cerulean as a super-exciting proof-of-concept client, demonstrating how social media could work on Matrix, with native threading, profiles-as-rooms, decentralised reputation, and (shortly) peeking-over-federation.
  • We completely rewrote matrix.to and relaunched it as a much more capable and friendly permalink redirection service; a precursor to finally getting matrix:// URLs everywhere!
  • We certainly didn’t predict that the “how to install Synapse” video tutorial published at the beginning of the COVID-19 pandemic would end up with 25.5K views (and counting…)

Then, there’s whole new waves of exciting stuff going on. The most obvious has to be the amount of Government uptake we’ve seen with Matrix this year, following on from France embracing Matrix across the public sector last year. Firstly the German armed forces announced their transition to Matrix, and then the German states of Schleswig-Holstein and Hamburg announced a mammoth 500K user Matrix deployment for education and public administration. Meanwhile, North Rhine Westphalia (the biggest state in Germany) launched their own Matrix-powered messager for education; loads of different universities have rolled out Matrix for collaboration - and we hear Famedly is making good progress with Matrix-powered healthcare messaging solutions. Finally, outside of Germany, we’re seeing the first official deployments in the UK government and US federal government - we’ll share details where possible (but sometimes big deployments of encrypted communication systems want to remain discreet). It’s incredibly exciting to see Matrix spreading across the public sector and education, and we’re hoping this will follow a similar pattern to how the Internet, email or indeed the Web first developed: a mix of high profile public sector deployments, complemented by a passionate grass-roots technical community, eventually spreading to span the rest of society :).

Another exciting thing which emerged this year is the amazing academic work that Karlsruhe Institute of Technology’s Decentralized Systems and Network Services Research Group has been conducting on Matrix. This really came on the radar back in June when their Matrix Decomposition: Analysis of an Access Control Approach on Transaction-based DAGs without Finality paper was published - a truly fascinating analysis of how state resolution works in Matrix, and how we manage to preserve access control within rooms without using blockchain-style ‘sealed blocks’ (and has helped fix a few nasty bugs!). I’m not sure any of us realised that Matrix’s state resolution counts as a new field of research, but it’s been great to follow along with their independent work. Most recently, and even more excitingly, they’re circulating a preview of their Analysis of the Matrix Event Graph Replicated Data Type paper - a deep analysis of the properties of Matrix DAGs themselves. We highly recommend reading the papers (what better way to spend the holiday break!). To give a taste, the final paragraph of the paper concludes:

MEG summary

2020 has also seen the arrival and maturation of a whole new generation of Matrix clients - Hydrogen is really impressive as an experimental next-generation Web (and Mobile Web) client; an account with 3000 rooms that uses 1.4GB of RAM on Element Web uses 14MB of RAM on Hydrogen and launches instantly, complete with excellent E2EE implementation. It even works on MSIE! The whole app, including dependencies, is about 70KB of code (200KB including Olm). Meanwhile, matrix-rust-sdk is coming along well, providing a general purpose native library for writing excellent native Matrix clients. Fractal merged initial matrix-rust-sdk a few weeks ago, and we’ll be experimenting with switching to it in Element iOS and Element Android (for its e2ee) in the coming year. It’s not inconceivable to think of a world where matrix-rust-sdk ends up being the no-brainer official SDK for native apps, and Hydrogen’s SDK becomes the no-brainer official SDK for JS apps.

Meanwhile, in the community, there’s been so much activity it’s untrue. But on the subject of maturing apps, it’s been incredibly exciting to see NeoChat emerge as an official KDE Matrix client (built on libQuotient and Kirigami, forked from Spectral), FluffyChat going from strength to strength; Nheko continuing to mature impressively; Mirage appearing out of nowhere as a fully featured desktop client; Fractal merging matrix-rust-sdk etc. On the serverside, Conduit was the big community story of the year - with an incredibly fast Rust + Sled server appearing out of the blue, with viable federation coming up on the horizon. The best bet for an overview of all things community is to checkout the TWIM backlogs however - there’s simply way too much stuff to mention it all here.

Obviously, no 2020 wrap-up post would be complete without acknowledging the COVID-19 pandemic - which increased focus on Matrix and other remote collaboration technology more than anyone could have predicted (especially given all the privacy missteps from Zoom, Teams and others). One of the highlights of the year was seeing the HOPE (Hackers On Planet Earth) conference shift their entire proceedings over to Matrix - turning the conference into a 10 day television station of premium hacking content, with Matrix successfully providing the social glue to preserve a sense of community despite going virtual. Similarly, we’re incredibly excited that FOSDEM 2021 is highly likely to run primarily via Matrix (with bridges to IRC and XMPP, of course) - our work is going to be cut out for us in January to ensure the amazing atmosphere of FOSDEM is preserved online for the >8,500 participants and ~800 talks. And if any other event organisers are reading this - please do reach out if you’re interested in going online via Matrix: we want Matrix to be the best possible ecosystem for online communities, including virtual events, and we’ll be happy to help :)

Talking of FOSDEM, a really fun bit of work which landed in Element this year was to (finally!) polish Widgets: the ability to embed arbitrary webapps into Matrix chatrooms. This includes being able to embed widgets in the RightPanel on Element Web, the LeftPanel too, add as many as you like to a room, resize them(!), and generally build much more sophisticated dashboards of additional content. Modal and fullscreen widgets are coming too, as are ways to simplify and unify access control. It turns out that these have arrived in the nick of time for events like FOSDEM, where we’re expecting to very heavily use widgets to embed video streams, video conferences, schedules, and generally automate the workflow of the conference via adding in web UIs as widgets wherever necessary. The work for this has been driven by the various German education deployments, where the same tricks are invaluable for automating online learning experiences. We originally wrote Widgets back in 2017 as a proof-of-concept to try to illustrate how chatrooms could be used to host proper custom UIs, and it's fantastic to see that dream finally come of age.

Finally, it’s been really exciting to see major progress in recent months on what’s essentially a whole new evolution of Matrix. Two years ago, a quiet patch during the Christmas holidays gave birth to a whole bunch of wild science fiction Matrix Spec Changes: MSC1772: Spaces (groups as rooms), MSC1769: Profiles as rooms, MSC1767: Extensible events, MSC1776: Peeking over /sync, MSC1777: Peeking over federation, etc. This was in part trying to ensure that we had something to look forward to when we emerged from the tunnel of launching Matrix 1.0, and in part trying to draw a coherent high-level sketch of what the next big wave of Matrix features could look like. Inevitably the MSCs got stuck in limbo for ages while we exited beta, launched Matrix 1.0, turned on E2EE by default etc - but in the latter half of this year they’ve hit the top of the todo list and it’s been incredibly exciting to see entirely new features landing once again. Implementation for Spaces is in in full swing and looking great; Profiles-as-rooms are effectively being trialled in Cerulean; Peeking over /sync has landed in Dendrite and peeking over federation is in PR (and unlocks all sorts of desirable features for using rooms more generically than we have today, including Spaces). Only Extensible events remains in limbo for now (we have enough to handle getting the others landed!)

Of these, Spaces has turned out to be exciting in wholly unexpected ways. While prototyping the UX for how best to navigate hierarchies of spaces, we had a genuine epiphany: the ability for anyone to define and share arbitrary hierarchies of rooms makes Matrix effectively a global decentralised hierarchical file system (where the ‘files’ are streams of realtime data, but can obviously store static content too). The decentralised access controls that KIT DSN wrote about could literally be file-system style access controls; enforcing access on a global decentralised hierarchy. We obviously have shared hierarchical filesystems today thanks to Dropbox and Google Drive, but these of course are centralised and effectively only store files - whereas Spaces could potentially scale to the whole web. In fact, you could even think of Spaces as flipping Matrix entirely on its head: the most defining building block going forwards could be the Spaces themselves rather than the rooms and events - just as directories are intrinsic to how you navigate a conventional filesystem. How has Matrix got this far without the concept of folders/directories?!

Right now these thoughts are just overexcited science fiction, but the potential really is mindblowing. It could give us a global read/write web for organising any arbitrary realtime data - with the social controls via ACLs to delegate and crowdsource curation of hierarchies however folks choose. The Matrix.org Foundation could seed a ‘root’ hierarchy, go curate all the rooms we know about into some Linnean-style taxonomy, delegate curation of the various subspaces to moderators from the community, and hey presto we’ve reinvented USENET… but with modern semantics, and without the rigid governance models. Hell, we could just mount (i.e. bridge) USENET straight into it. And any other hierarchical namespace of conversations you can think of - Google Groups, Stackoverflow, Discourse, IMAP trees…

Of course, the initial Spaces implementation is going to be focused of on letting communities publish their existing rooms, and users organise their own rooms, rather than managing an infinite ever-expanding global space hierarchy - but given we’ve been designing Spaces to support government (and inter-government) scales of Spaces, it’s not inconceivable to think we could use it to navigate gigantic public shared Spaces in the longer term.

Anyway, enough Space scifi - what’s coming up in 2021?

2021

Our current hit list is:

  • Spaces - see above :)
  • Social Login - we’re going to be making Single Sign On (SSO) a proper first-class citizen in Matrix (and Synapse and Element) in the coming weeks, and enabling it on the matrix.org homeserver, so users can do single-click logins via Github/Gitlab/Google and other SSO providers. Obviously this means your Matrix identity will be beholden to your identity provider (IdP), but this may well be preferable for many users who just want a single-click way to enter Matrix and don’t care about being tied to a given IdP.
  • VoIP - we have a lot of work in flight at the moment to make 1:1 VoIP super robust. Some of it has already landed in Element, but the rest will land in the coming weeks - and then we’re hoping to revisit Matrix-native group voice/video.
  • Voice messaging - we’re hoping to finally add voice messaging to Element (and Matrix)
  • Location sharing - ...and this too.
  • P2P - Lots of P2P work on the horizon, now Dendrite is increasingly stable. First of all we need to iterate more on Pinecone, our pre-alpha next-generation P2P overlay network - and then sort out account portability, and privacy-preserving store-and-forward. We’re hoping to see the live P2P Matrix network turn on this year, however, and ideally see homeservers (probably Dendrite) multihoming by default on both today’s Matrix as well as the P2P network, acting as gateways between the two.
  • Threads - Cerulean is excellent proof for how threading could work in Matrix; we just need to get it implemented in Element!
  • Peeking - Peeking is going to become so much more important for participating in non-chat rooms, such as Spaces, Profiles, Reputation feeds, etc. We’ll finish it in Dendrite, and then implement it in Synapse too.
  • Decentralised Reputation - Cerulean has the first implementation of decentralised reputation for experimentation purposes, and we’ll be working solidly on it over the coming year to empower users to counter abuse by applying their own subjective reputation feeds to their content.
  • Incremental Signup - Once upon a time, Element (Riot) had the ability to gradually sign-up without the user even really realising they’d signed up. We want to bring it back - perhaps this will be the year?
  • DMLS - with the first MLS messages flowing over Matrix, we want to at least provide MLS as an option alongside Megolm for encryption. It should be radically more performant in larger rooms (logarithmic rather than linear complexity), but lacks deniability (the assurance that you cannot prove a user said something in retrospect, in order to blackmail them or similar), and is still unproven technology. We’ll aim to prove it in 2021.
  • E2EE improvements - We improved E2EE immeasurably in 2020; turning it on by default, adding cross-signing, QR code verification etc. But usability and reliability can still be improved. We’ll be looking at further simplifying the UX, and potentially combining together your login password and recovery/security passphrase so you only have one password to remember going forwards.
  • Hydrogen - We’ll keep polishing Hydrogen, bringing it towards feature parity with Element, ensure its SDK is available for other clients, and start seeing how we can use it in Element itself. For instance, the Spaces-aware RoomList in Element may well end up stealing alien technology from Hydrogen.
  • matrix-rust-sdk - Similarly, we’ll keep polishing matrix-rust-sdk; stealing inspiration from Hydrogen’s state model, and start migrating bits of the native mobile Element apps to use it.
  • The Spec - get Will’s new spec website live, and get improving all the surrounding material too.

I’m sure I’m missing lots here, but these are the ones which pop immediately to mind. You can also check Element's public roadmap, which covers all the core Matrix work donated by Element (as well as everything else Element is getting up to).

As always, huge huge thanks goes to the whole Matrix community for flying Matrix and keeping the dream alive and growing faster than ever. It’s been a rough year, and we hope that you’ve survived it intact (and you have our sincere sympathies if you haven’t). Let’s hope that 2021 will be a massive improvement, and that the whole Matrix ecosystem will continue to prosper in the new year.

-- Matthew, Amandine, and the whole Matrix team.

Introducing Cerulean

2020-12-18 — General — Matthew Hodgson

Hi all,

We have a bit of an unexpected early Christmas present for you today…

Alongside all the normal business-as-usual Matrix stuff, we’ve found some time to do a mad science experiment over the last few weeks - to test the question: “Is it possible to build a serious Twitter-style decentralised microblogging app using Matrix?”

It turns out the answer is a firm “yes” - and as a result we’d like to present a very early sneak preview of Cerulean: a highly experimental new microblogging app for Matrix, complete with first-class support for arbitrarily nested threading, with both Twitter-style (“vertical”) and HN/Reddit-style (“horizontal”) layout… and mobile web support!

Cerulean screenie

Cerulean is unusual in many ways:

  • It’s (currently) a very minimal javascript app - only 2,500 lines of code.
  • It has zero dependencies (other than React).
    • This is to show just how simple a fairly sophisticated Matrix client can be...
    • ...and so the code can be easily understood by folks unfamiliar with Matrix...
    • ...and so we can iterate fast while figuring out threading...
    • ...and because none of the SDKs support threading yet :D
  • It relies on MSC2836: Threading - our highly experimental Matrix Spec Change to extend relationships (as used by reaction & edit aggregations) to support free-form arbitrary depth threading.
  • As such, it only works on Dendrite, as that’s where we’ve been experimenting with implementing MSC2836. (We’re now running an official public Dendrite server instance at dendrite.matrix.org though, which makes it easy to test - and our test Cerulean instance https://cerulean.matrix.org points at it by default).

This is very much a proof of concept. We’re releasing it today as a sneak preview so that intrepid Matrix experimenters can play with it, and to open up the project for contributions! (PRs welcome - it should be dead easy to hack on!). Also, we give no guarantees about data durability: both Cerulean and dendrite.matrix.org are highly experimental; do not trust them yet with important data; we reserve the right to delete it all while we iterate on the design.

What can it do?

So for the first cut, we’ve implemented the minimal features to make this something you can just about use and play with for real :)

  • Home view (showing recent posts from folks you follow)
  • Timeline view (showing the recent posts or replies from a given user)
  • Thread view (showing a post and its replies as a thread)
  • Live updating (It’s Matrix, after all! We’ve disabled it for guests though.)
  • Posting plain text and images
  • Fully decentralised thanks to Matrix (assuming you’re on Dendrite)
  • Twitter-style “Vertical” threading (replies form a column; you indent when someone forks the conversation)
  • HN/Reddit/Email-style “Horizontal” threading (each reply is indented; forks have the same indentation)
  • Basic Registration & Login
  • Guest support (slightly faked with non-guest users, as Dendrite’s guest support isn’t finished yet)
  • Super-experimental proof-of-concept support for decentralised reputation filtering(!)

Obviously, there’s a huge amount of stuff needed for parity with a proper Twitter-style system:

  • Configurable follows. Currently the act of viewing someone’s timeline automatically follows them. This is because Dendrite doesn’t peek over federation yet (but it’s close), so you have to join a room to view its contents - and the act of viewing someone’s timeline room is how you follow them in Cerulean.
  • Likes (i.e. plain old Matrix reactions, although we might need to finally sort out federating them as aggregations rather than individually, if people use them like they use them on Twitter!)
  • Retweets (dead easy)
  • Pagination / infinite scrolling (just need to hook it up)
  • Protect your posts (dead easy; you just switch your timeline room to invite-only!)
  • Show (some) replies to messages in the Home view
  • Show parent and sibling context as well as child context in the Thread view
  • Mentions (we need to decide how to notify folks when they’re mentioned - perhaps Matrix’s push notifications should be extended to let you subscribe to keywords for public rooms you’re not actually in?)
  • Notifications (although this is just because Dendrite doesn’t do notifs yet)
  • Search (again, just needs to be implemented in Dendrite - although how do you search beyond the data in your current homeserver? Folks are used to global search)
  • Hashtags (it’s just search, basically)
  • Symlinks (see below)
  • Figure out how to handle lost unthreaded messages (see below)
  • Offline support? (if we were using a proper Matrix SDK, we’d hopefully get this for free, but currently Cerulean doesn’t store any state locally at all).

How does it work?

Every message you send using Cerulean goes into two Matrix rooms, dubbed the "timeline" room and the "thread" room. The "timeline" room (with an alias of #@matthew:dendrite.matrix.org or whatever your matrix id is) is a room with all of your posts and no one else's. The "thread" room is a normal Matrix room which represents the message thread itself. Creating a new "Post" will create a new "thread" room. Replying to a post will join the existing "thread" room and send a message into that room. MSC2836 is used to handle threading of messages in the "thread” room - the replies refer to their parent via an m.relationship field in the event.

These semantics play nicely with existing Matrix clients, who will see one room per thread and a flattened chronological view of the thread itself (unless the client natively supports MSC2836, but none do yet apart from Cerulean). However, as Cerulean only navigates threaded messages with an m.reference relationship (eg it only ever uses the new /event_relationships API rather than /messages to pull in history), normal messages sent by Matrix into a thread or timeline room will not yet show up in Cerulean.

In this initial version, Cerulean literally posts the message twice into both rooms - but we’re also experimenting with the idea of adding “symlinks” to Matrix, letting the canonical version of the event be in the timeline room, and then the instance of the event in the thread room be a ‘symlink’ to the one in the timeline. This means that the threading metadata could be structured in the thread room, and let the user do things like turn their timeline private (or vice versa) without impacting the threading metadata. We could also add an API to both post to timeline and symlink into a thread in one fell swoop, rather than manually sending two events. It’d look something like this:

Cerulean diagram

We also experimented with cross-room threading (letting Bob’s timeline messages directly respond to Alice’s timeline messages and vice versa), but it posed some nasty problems - for instance, to find out what cross-room replies a message has, you’d need to store forward references somehow which the replier would need permission to create. Also, if you didn’t have access to view the remote room, the thread would break. So we’ve punted cross-room threading to a later MSC for now.

Needless to say, once we’re happy with how threading works at the protocol level, we’ll be looking at getting it into the UX of Element and mainstream Matrix chat clients too!

What’s with the decentralised reputation button?

Cerulean is very much a test jig for new ideas (e.g. threading, timeline rooms, peeking), and we’re taking the opportunity to also use it as an experiment for our first forays into publishing and subscribing to reputation greylists; giving users the option to filter out content by default they might not want to see… but doing so on their own terms by subscribing to whatever reputation feed they prefer, while clearly visualising the filtering being applied. In other words, this is the first concrete experimental implementation of the work proposed in the second half of Combating Abuse in Matrix without Backdoors. This is super early days, and we haven’t even published a proto-MSC for the event format being used, but if you’re particularly interested in this domain it’s easy enough to figure out - just head over to #nsfw:dendrite.matrix.org (warning: not actually NSFW, yet) and look in /devtools to see what’s going on.

So, there you have it - further evidence that Matrix is not just for Chat, and a hopefully intriguing taste of the shape of things to come! Please check out the demo at https://cerulean.matrix.org or try playing with your own from https://github.com/matrix-org/cerulean, and then head over to #cerulean:matrix.org and let us know what you think! :)

Matrix.to: Reloaded

2020-12-17 — General — Nad Chishtie

One of the goals on the core team is to reduce friction for new users joining Matrix. A challenge we regularly face is all the factors which make Matrix flexible and powerful as an open, secure decentralised protocol also increase the difficulty of getting started.

As one example— to create a healthy, vibrant ecosystem and put power back into the hands of end users, it’s critical multiple clients exist, and that users ultimately have control over which one to use. However, needing to choose a client before getting going is counter-intuitive, and adds cognitive load which proprietary services simply don’t have.

Striking this balance is tricky, and one we’re aiming to improve with the latest version of Matrix.to.

What's Matrix.to?

Matrix.to is a simple URL redirection service which lets users share links to rooms, users and communities. It isn’t tied to any client, and for end users it serves as a landing page for many as their first touch to Matrix. And until the matrix:// URI scheme is deployed commonplace (we finally registered it with IANA a few months ago!) it is the only client-agnostic way to link to content in Matrix.

It’s privacy preserving, with no information stored server side, with all calculation done in client-side JavaScript. It started life years ago as a temporary minimum viable hack by Matthew which then hung around untouched for years being… minimally viable. But we’ve recently given it a huge upgrade in usability and functionality at last!

What's new?

The matrix.to room, on the new matrix.to!

We’ve re-written matrix.to from scratch, giving it a visual upgrade and refocused the experience around:

  1. Helping new users find the best client for them to easily get going. By default, links will prioritise showing clients which are compatible with the platform the link is being viewed from, including mobile platforms.

  2. Optionally, remembering your preferred client for future visits. This also includes deeplinking into native apps for Element Desktop & Element Mobile (and in future, other clients too, of course).

  3. Fetching useful previews. One of our main observations when testing with new users is a lack of confidence trying out a new service without personalised, contextual information on the rooms or people they’re heading to. Matrix.to now displays room metadata like avatars, names and topics directly (fetched via matrix.org by default, asking for permission).

What's next?

We’ve baked in the ability to specify clients and deployments within links, allowing sharing to give the option of a specific destination to guarantee a predictable experience. For instance, Mozilla might share matrix.to links which recommend using chat.mozilla.org, if you don’t already have a preferred Matrix client configured. We’ve yet to implement this feature in Element, but we’ll be researching and experimenting with different implementations soon and will recommend best practises when we have them.

We plan to evolve matrix.to over time, including eventually evolving it to better support the Matrix URI scheme. As before, you can find the source code on GitHub and please go ahead and submit pull requests to get your Matrix client listed.

Let us know what you think over in the matrix.to room, linked to via matrix.to!

Dendrite 2020 Progress Update

2020-12-15 — General — Neil Alexander

It's been a year since Dendrite development picked up again and it's certainly been a busy one at that! We started off 2020 by sprinting to complete the FOSDEM P2P demo and, since then, we have continued to develop Dendrite into a more featureful and stable homeserver.

In October, we moved Dendrite into beta, and have since released a number of releases. We've also seen quite a lot of interest from the community, so I'm here today to write about some of the fun things that have been going on in Dendrite-land.

Announcing dendrite.matrix.org

I'm happy to announce that we've finally deployed our own public Dendrite instance at dendrite.matrix.org! It's running the latest Dendrite code and is open for registration, so if you have been looking for an opportunity to play with Dendrite without hosting your own deployment, here's your chance!

There are still bugs and missing features, but overall the server is quite usable, so please feel free to register and try it and let us know how you get on.

This is the first deployment that we've built for any kind of scale, so we are cautious of the fact that there may be performance bottlenecks still. That said, over the last few weeks, a number of performance-improving changes have been merged, including:

  • Around 20x performance improvement on the State Resolution v2 algorithm, which is used in room versions 2 and above
  • Significantly reducing the amount of time spent recalculating event reference hashes and event IDs in the roomserver and sync API, reducing CPU usage
  • Optimised memory usage and reduced database hits in the federation sender, which helps particularly in large rooms with lots of resident servers

We're optimistic that running this deployment will help us to identify scaling pain points and to make Dendrite leaner in the long run. Feel free to sign up and give it a spin! :-)

Features

Since the beginning of the year, we've added a number of new features, including but not limited to:

  • Room versions support for all currently specced versions (v1-v6), including support for State Resolution v2
  • SQLite storage support in addition to PostgreSQL, largely useful for the P2P demos
  • Support for database schema upgrades, making updating Dendrite significantly easier
  • Early end-to-end encryption support, including device list syncing and send-to-device messages, although with key backup and cross-signing still to come
  • A number of federation features, including invites, retries and backing off unreachable homeservers
  • User-interactive authentication (UIA), which is used in password changes and deleting devices from your device list
  • Support for local pagination, backfilling over federation and fetching missing events
  • Redaction of events both locally and over federation
  • Entirely new microservices for managing server signing keys, E2E keys, user and device management
  • Lots of great contributions from the community - including all of Read Receipts (thanks to S7evinK) and Read Markers (thanks to Lesterpig)!

...and of course entered Beta in October!

Spec compliance

Of course, Dendrite also needs to be able to fulfill the promise of being a usable next-generation Matrix homeserver at the same time as being a sci-fi development platform. We have spent much of the last year working specifically on this. Today, Dendrite's Sytest compliance sits at:

  • 59% compliance for Client-Server APIs, up from 33% in May 2020
  • 83% compliance for Server-Server APIs, up from 26% in May 2020

As you can see, these are significant leaps in the numbers of tests passing against Dendrite.

Experimental MSCs

We have been increasingly trying to use Dendrite for the development and testing of some new Matrix feature proposals. Recently we've seen early support added for Peeking (MSC2753) and there is work in progress on Peeking over Federation (MSC2444).

Peeking enables temporarily subscribing to a room for real-time events without joining the room. This will only be possible with rooms that are world-readable, but it reduces the overhead of looking into a room significantly as there is no need to update the room state for each peeking user/device.

In addition to that, we've also been working on Threading (MSC2836) support, which is the gateway to building some pretty new and interesting Matrix experiences. Twitter-like or Reddit-like social prototypes like this have traditionally been difficult to build on top of Matrix as the m.reference relation type from MSC1849 had never really been fleshed out.

Threading adds m.relationship fields for embedding these relationships, and also specifies an additional /event_relationships API endpoint for finding other events related to a given event in either direction. This makes it possible to build threads.

P2P Matrix

Dendrite has also been our primary development platform for P2P Matrix. This year we have released multiple P2P Matrix demos, including:

  • p2p.riot.im, which uses libp2p rendezvous and embeds a full Dendrite homeserver into an in-browser Service Worker
  • Element iOS P2P, available on TestFlight, which embeds a full Dendrite homeserver into the Element iOS app, initially using QUIC over Yggdrasil as a transport for federation traffic, but with more recent versions using QUIC over the experimental Pinecone protocol
  • dendrite-demo-libp2p, a standalone binary which formed the basis of the FOSDEM 2020 P2P demo, using libp2p and local multicast discovery as a transport for federation traffic
  • dendrite-demo-yggdrasil, another standalone binary like above, but using QUIC over Yggdrasil connectivity instead of libp2p as the transport for federation traffic

Each experiment teaches us more about potential issues that need to be resolved in order to bring P2P Matrix closer to being reality, and we are continuing to use Dendrite for this work. We'll be announcing more information in the New Year about our latest efforts and the Pinecone routing scheme that we are developing.

It's also worth highlighting that all of the other experimental work taking place right now, including Threading and Peeking, also work over P2P!

What's next

We'll be taking a short break for Christmas, but will then be continuing work on Dendrite in 2021, with the main aims being to add new features, improve spec compliance further, fix bugs and eventually exit beta. We'll also be continuing further experimental work in the P2P and Threading areas, as well as supporting the development of new MSCs such as Portable Identities (MSC2787).

We'd like to say thank you for the community support and interest, and also to send out a special thanks to our community contributors who have contribued a number of fixes and features in recent months! We always welcome code contributions via GitHub if you are an interested developer.

As always, stay tuned for more Dendrite updates either by joining us in #dendrite:matrix.org or by getting your regular dose of This Week in Matrix!

— Neil Alexander and Kegan

Gitter now speaks Matrix!

2020-12-07 — General — Matthew Hodgson

Hi all,

It’s been just over 2 months since we revealed that Gitter was going to join Matrix - and we are incredibly proud to announce that Gitter has officially turned on true native Matrix connectivity: all public Gitter rooms are now available natively via Matrix, and all Gitter users now natively exist on Matrix. So, if you wanted to join the official Node.js language support room at https://gitter.im/nodejs/node from Matrix, just head over to #nodejs_node:gitter.im and *boom*, you’re in!

This means Gitter is now running a Matrix homeserver at gitter.im which exposes all the active public rooms - so if you go to the the room directory in Element (for instance) and select gitter.im as a homeserver, you can jump straight in:

Gitter room directory

Once you’re in, you can chat back and forth transparently between users on the Gitter side and the Matrix side, and you no longer have the ugly “Matrixbot” user faking the messages back and forth - these are ‘real’ users talking directly to one another, and every public msg in every public room is now automatically exposed into Matrix.

Gitter and Matrix going native!

So, suddenly all the developer communities previously living only in Gitter (Scala, Node, Webpack, Angular, Rails and thousands of others) are now available to anyone anywhere on Matrix - alongside communities bridged from Freenode and Slack; the native Matrix communities for Mozilla, KDE, GNOME communities etc. We’re hopeful that glueing everything together via Matrix will usher in a new age of open and defragmented dev collaboration, a bit like we used to have on IRC, back in the day.

This is also great news for mobile Gitter users - as the original mobile Gitter clients have been in a holding pattern for over a year, and native Matrix support for Gitter means they are now officially deprecated in favour of Element (or indeed any other mobile Matrix client).

What features are ready?

Now, this is the first cut of native Matrix support in Gitter: much of the time since Gitter joined Element has been spent migrating stuff over from Gitlab to Element, and it’s only really been a month of work so far in hooking up Matrix. As a result: all the important features work, but there’s also stuff that’s yet to land:

Features ready today:

  • Ability to join rooms from Matrix via #org_repo:gitter.im
  • Bridging Edits, Replies (mapped to Threads on Gitter), Deletes, File transfer
  • Bridging Markdown & Emoji

What remains:

  • Ability to send/receive Direct Messages
  • Ability to plumb existing Matrix rooms into Gitter natively
  • Ability to view past Gitter history from Matrix. This is planned thanks to https://github.com/matrix-org/matrix-doc/pull/2716
  • Synchronising the full Gitter membership list to Matrix. Currently the membership syncs incrementally as people speak
  • Turning off the old Gitter bridge
  • Bridging emotes (/me support) (almost landed!)
  • Bridging read receipts
  • Synchronising room avatars
  • Bridge LaTeX

Stuff we’re not planning to support:

  • Ability to join arbitrary rooms on Matrix from Gitter. This could consume huge resources on Gitter, and we’re not in a rush to mirror all of Matrix into Gitter. This will get addressed when Gitter merges with Element into a pure Matrix client.
  • Bridging Reactions. Gitter doesn’t have these natively today, and rather than adding them to Gitter, we’d rather work on merging Gitter & Element together.

For more details, we strongly recommend checking out the native Matrix epic on Gitlab for the unvarnished truth straight from the coal-face!

How do you make an existing chat system talk Matrix?

In terms of the work which has gone into this - Gitter has been an excellent case study of how you can easily plug an existing large established chat system into Matrix.

At high level, the core work needed was as simple as:

  • Add ‘virtual users’, so remote Matrix users can be modelled and represented in Gitter correctly: https://gitlab.com/gitterHQ/webapp/-/merge_requests/2027/diffs.
    • This can be accomplished by simply adding a virtualUser property to your chat message/post/tweet schema which holds the mxid, displayName, and avatar as an alternative to your author field. Then display the virtualUser whenever available over the author.
  • Add an application service to Gitter to bridge traffic in & out of Matrix: https://gitlab.com/gitterHQ/webapp/-/merge_requests/2041/diffs
    • This "application service" comes pre-packaged for you in many cases, so for example you can simply drop in a library like matrix-appservice-bridge in a Node.js application, and all of the Matrix talking complexity is handled for you.
  • Polish it!

In practice, Eric (lead Gitter dev) laid out the waypoints of the full journey:

  1. First big step was to add the concept of virtual users to Gitter. We could also have created a new Gitter user for every new matrix ID that appears, but tagging them as virtual users is a bit cleaner.
  2. Figuring out how to balance the Matrix traffic coming into/out of Gitter.
    1. Spreading the inbound load comes for free via our existing load-balancer setup (ELB) where we already have 8 webapp servers running the various services of gitter.im. We just run the Matrix bridge on those servers alongside each web and api process, and then the load-balancer’s matrix.gitter.im spreads out to the servers.
    2. Events from Matrix then hit the load balancer and reach one of the servers (no duplication when processing events).
    3. If something on Gitter happens, the action occurs on one server and we just propagate it over to Matrix (no duplication or locking needed).
  3. We have realtime websockets and Faye subscriptions already in the app which are backed by Mongoose database hooks whenever something changes. We just tapped into the same thing to be able to bridge across new information to Matrix as we receive it on Gitter.
  4. Hooking up the official Matrix bridging matrix-appservice-bridge library to use Gitter’s existing MongoDB for storage instead of nedb.
  5. Figuring out how to namespace the mxids of the gitter users:
    1. It’s nice to have the mxid as human readable as possible instead of just the numerical userId in your service.
    2. But if people can change their username in your service, you can’t change your mxid on Matrix. In the future, we’ll have portable accounts in Matrix to support this (MSC2787) but sadly these are still vapourware at this point.
    3. If you naively just switch the user’s mxid when they rename their username, then you could end up leaking conversation history between mxids(!)
    4. So we went with @username-userid:gitter.im for the Matrix ID to make it a bit more human readable but also unique so any renames can happen without affecting anything.
  6. For room aliases, we decided to change our community/room URI syntax to underscores for the room aliases, #community_room:gitter.im
  7. Figuring out how to bridge features correctly;
    1. Emoji - mapping between :shortcode: and unicode emojis
    2. Mapping between Gitter threaded conversations <-> Matrix replies
    3. Mapping between Matrix mentions and Gitter mentions
  8. Keeping users and room data in sync
    1. We haven’t gotten there yet, but the data comes through the same Mongoose hook and we can update the bridged data as they change on the Gitter end.

Meanwhile, the Matrix side of gitter.im is hosted by Element Matrix Services and is a plain old Synapse, talking through to Gitter via the Application Service API. An alternative architecture would be to have got Gitter directly federating with Matrix by embedding a “homeserver library” into it (e.g. embedding Dendrite). However, given Dendrite is still beta and assumes it is storing its data itself (rather than persisting in an existing backend such as Gitter’s mongodb), we went for the simpler option to start with.

It’s been really interesting to see how this has played out week by week in the Gitter updates in This Week in Matrix: you can literally track the progress and see how the integration came to life between Oct 9, Oct 23, Nov 6, Nov 27 and finally Dec 4.

Huge thanks go to Eric Eastwood, the lead dev of Gitter and mastermind behind the project - and also to Half-Shot and Christian who’ve been providing all the support and review from the Matrix bridging team.

What’s next?

First and foremost we’re going to be working through the “What remains” section of the list above: killing off the old bridge, sorting out plumbed rooms, hooking up DMs, importing old Gitter history into Matrix, etc. This should then give us an exceptionally low impedance link between Gitter & Matrix.

Then, as per our original announcement, the plan is:

In the medium/long term, it’s simply not going to be efficient for the combined Element/Gitter team to split our efforts maintaining two high-profile Matrix clients. Our plan is instead to merge Gitter’s features into Element (or next generations of Element) itself and then - if and only if Element has achieved parity with Gitter - we expect to upgrade the deployment on gitter.im to a Gitter-customised version of Element. The inevitable side-effect is that we’ll be adding new features to Element rather than Gitter going forwards.

Now, that means implementing some features in Matrix/Element to match...

  • Instant live room peeking (less than a second to load the webapp into a live-view of a massive room with 20K users!!)
  • Seamless onboarding thanks to using GitLab & GitHub for accounts
  • Curated hierarchical room directory
  • Magical creation of rooms on demand for every GitLab and GitHub project ever
  • GitLab/GitHub activity as a first-class citizen in a room’s side-panel
  • Excellent search-engine-friendly static content and archives
  • KaTeX support for Maths communities
  • Threads!

...and this work is in full swing:

The only bits which aren’t already progressing yet are tighter GL/GH integration, and better search engine optimised static archives.

So, the plan is to get cracking on the rest of the feature parity, then merge Gitter & Element together - and meanwhile continue getting the rest of the world into Matrix :)

We live in exciting times: open standards-based interoperable communication is on the rise again, and we hope Gitter’s new life in Matrix is the beginning of a new age of cross-project developer collaboration, at last escaping the fragmentation we’ve suffered over the last few years.

Finally, please do give feedback via Gitter or Matrix (or mail!) on the integration and where you’d like to see it go next!

Thanks for flying Matrix and Gitter,

-- The Matrix Team

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