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Reflect – Multiplayer web app framework with game-style synchronization

rocicorp.dev

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Re: Reflect – Multiplayer web app framework with game-style synchronization

#131

Post by tablatom »

moralestapia wrote: post #81
aboodman wrote: post #79

Earlier quoted context omitted.

Hi! Thanks for the thoughtful question. >List operations just work: Fair point. Will change. What I really meant here was "(Many) list operations just work" (just like above I said "all kinds of things just work". > All updates reach the server at the same time. What is the solution to that? Timestamps? Fallback to LLW? There are a number of issues you might be pointing out, and I'm not sure which one you mean. In ge…

>nothing can fix this Exactly. >For these problems, undo and presence indicators go a long way to avoid these problems through human/social mechanisms. x1,000 to this. This guy builds . That's exactly my takeaway as well from years working on this; provide a solid (by that I mean clearly defined) deterministic algo, and solve the rest w/ UX.

This points towards a big challenge that I think gets overlooked way too often. A lot of these sync libraries/frameworks claim to solve for both real-time interaction, and local-first, sync when you reconnect. But the UX needs are wildly different.

For the former you want (as mentioned) good presence info and undo. For the latter you (sometimes) want explicitly flagged conflicts and manual resolution, like we have in git etc.

With the Replicache/Reflect model, you could actually handle both approaches. Might not be easy but the model can support it.

Re: Reflect – Multiplayer web app framework with game-style synchronization

#132

Post by meheleventyone »

heron88 wrote: post #90

This looks great! I'm curious what the recommended use cases are for something like this. Is it worth adding the additional complexity for complex crud-y saas? I know Linear is built on this local-first model but from seeing their presentations on the challenges they've had scaling it, I'm left wondering if it makes sense for something like a full-featured CRM with hundreds of tables. Is Reflect/Replicache suited for…

My 2c as a game dev is that you really want to know the cases where you need real-time collaboration. Otherwise the still collaborative but slower updating techniques people normally use are perfectly fine. Even in something like an MMO parts of the game will use real-time game servers and others might just use a REST API.

The other side of it is to make sure that real-time collab is something users actually want and use. There’s a lot of froth at the moment about real-time but IMO and IME it has a much smaller set of useful cases than most people actually think. But where it is useful, it is a step up for collaboration.

For example with Google Docs I find myself and our broader team mostly solo write but collaboratively review and edit. Where we collaboratively write its carefully structured so people aren’t stomping on each other and often done with someone acting as a mediator.

Re: Reflect – Multiplayer web app framework with game-style synchronization

#133

Post by meheleventyone »

wheybags wrote: post #129
DecoPerson wrote: post #86

Earlier quoted context omitted.

Hey wheybags, this is not deterministic lockstep. That is an algorithm for peer-to-peer games, where each peer waits for the input from all other players before advancing the game simulation. The deterministic part is because players share inputs (not simulation results) AND the simulation is deterministic for the same inputs. The lockstep part is because all clients advance at a coordinated pace. The Age of Empires…

Yes, I know there's some differences in what you're doing here from classic deterministic lockstep, but the fundamental concept of syncing a queue of inputs from which the game state can be derived, instead of syncing the game state itself is the same, which is why I mentioned it. Also, while deterministic lockstep can be used peer to peer, it is not fundamentally a peer to peer model. Factorio for example, uses serv…

All multiplayer games sync a queue of messages to derive game state, that’s inherent in networking.

Deterministic lockstep means that the speed of the simulation is dependent on the slowest member as everyone waits to get all the inputs before advancing a frame. You’ll get literally pauses and jank if someone is on a poor connection. That’s not the case here.

The difference with this model of networking is what is synced in the lockstep case the simulation being deterministic means you only need to send inputs to keep the game in sync so you vastly reduce network traffic. In this case it’s not necessarily deterministic and the server sends back the new state to the clients after determining what it is as it’s the authority on what that state is. Clients can predict ahead by making the change locally but must correct mispredictions. In the deterministic case there can be no mispredictions and it’s a pain in the butt to ensure that your game is actually deterministic and resolving sync issues is a real pain.

Factorio sounds like it uses a deterministic model that doesn’t wait to run in lockstep and instead reconciles errors that causes. The typical way of doing that is to rollback to a prior state where the simulation diverged due to missing inputs and redo the following ticks. That’s probably prohibitively expensive given the scale of Factorio versus something simpler like a fighting game so I assume there is a hybrid model and some extra info is sent by an authoritative source that can be checked locally.

Re: Reflect – Multiplayer web app framework with game-style synchronization

#134

Post by anonzzzies »

Besides trystero which is great but depends on things I cannot get into our company, anything open source? I cannot get this into our company either as it's vital infra and as such needs to be replaceable with open source at will. We have that as a rule. The only things that are exceptions are necessary evil; payments & cloudflare (bot-fight specifically).

Re: Reflect – Multiplayer web app framework with game-style synchronization

#135

Post by wim »

Very elegant solution, and neat demo page!

I'm curious what trade-offs you looked at regarding sending state vs mutations from the server back to clients. As the server is authoritative, I imagine it could also send mutations to the clients in the order in which the server has determined parallel operations need to be resolved (and adjust mutations as needed to resolve conflicts or permissions issues). Clients would then need to rebase any pending local mutations, so that would involve more logic vs the data sent for mutations most likely being smaller than the "full" state of certain objects being updated?

Re: Reflect – Multiplayer web app framework with game-style synchronization

#137

Post by jamil7 »

cornfutes wrote: post #98

Looks great for a hobby project. Has anyone done the cost + risk assessment of building a for-profit product on top of this? Would love to know, as I am working on a web IDE with collaboration. There’s also the matter of obscuring client data from 3rd and even 1st party.

If what you're building on top of leaks into other parts of your codebase, can't be isolated and can't easily be swapped out, I'd say avoid building a product on top of it.

Re: Reflect – Multiplayer web app framework with game-style synchronization

#140

Post by hahn-kev »

holoduke wrote: post #124

When will it finally be possible to use UDP protocol within browsers? TCP got way too big overhead. A multiplayer engine in which you send 30 messages per second for 128 users is what i need. Not possible with websockets withput having super computers.

HTTP3 is your friend here
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