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For most apps just use SSE and the built-in code for making HTTP requests (Fetch) instead of hacking up your own client side JS to make requests over a WebSocket. The latency is the same because modern browsers multiplex HTTP requests over a single TCP connection that is left open.
Maybe if you are making many client requests per second there is an advantage to not sending full headers/cookies/etc... on each request but not if you're sending requests in response to user clicks/touches.
Any sufficiently complicated SPA contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Fetch.
In my experience this isn’t true; firstly you’re relying on an implementation detail of the platform that you’re executing on, of which you have no control over on the client side. Secondly, even if you aren’t opening a new connection per request, you’re still travelling through an entire HTTP stack implementation rather than the incredibly simple WebSocket protocol - effectively a length and a mask to get the contents, rather than some (in http1 land) fuzzy parser.
If you can guarantee you’re hitting http2 or http3 then you might be closer in latency, but due to the complexity of both I would imagine plain http1 negotiated persistent WebSockets provide the best latency.
Doing things on the client means user's CPU is doing some work which else would need to be done on the server, for maybe thousands of clients at the same time.
So I understand some people don't like JavaScript, but then I think the solution would be WebAssembly. I mean the point of distributed computting is that the computational load can be distributed. Perhaps counter-intuitively that often also means less need fo communications and latencies.
Unlike WebSockets, browser SSE also has a built-in recovery mechanism so you don't miss events across reconnects (`Last-Event-ID` header), although this does require explicit support from the server-side app.
Given that the WebSocket handshake has an additional round-trip, SSE would typically be faster in terms of time-to-first-byte.
> you’re still travelling through an entire HTTP stack implementation rather than the incredibly simple WebSocket protocol
Both protocols have their own minimal framing, but "an entire HTTP stack" is a stretch. It's hard to argue that `data:value\n\n` is more complex than the WebSocket binary protocol. Simplistic, sure (no binary payloads), but also simple enough to, say, pipe through a regex. Good luck doing that with WebSocket.
Sound advice otherwise, but you could have left this part out of the comment :D
You underestimate how many "sufficiently complicated SPAs" are slapped together low-code projects. Their maintainers have no idea what you're even talking about.
https://en.wikipedia.org/wiki/Greenspun's_tenth_rule
Here is the original: https://en.wikipedia.org/wiki/Greenspun%27s_tenth_rule
https://yagni.club/3mstlyuxe5s26
https://en.andros.dev/blog/bd74e61a/were-fighting-over-the-w...
Well, some drawbacks are not accounted for when replacing HTML parts: input elements lose focus, if some view was scrolled, then it gets unscrolled, jumping under user's pointer etc.
Pretty much every web app I build has this pattern in it from day 1, as they all quickly expand to have a realtime inbox and notifications subsystem to support workflows and agents.
I use Django Ninja, Zod, InertiaJS+Vue and its as easy as using Django's templating engine, but static typing ensures my view doesnt emit unrepresentable data, my TS doesnt accept unrepresentable data, Vue+TS dont allow logic errors in template. AI makes it effortless. Again, the loaded page is a function of the data supplied at the view.
With HTMX, I'm writing several server-side functions to mutate the DOM imperatively and using HTML attributes to call them. Its great for forms but that shopping cart example needs code scattered across multiple functions and templates.
This is definitely true for HTTP/0 and /1. Is it still true under HTTP/3, or has the underlying ‘single conduit, many channels’ model improved things if used correctly?
https://github.com/prettydiff/aphorio
My approach is pretty simple. Since the connection phase of WebSockets is RFC2616 compatible, per RFC6455, you can use the same server logic to connect both.
You don’t need a TCP connection for everything.
If you’re optimizing for that you can consider client-side caching which you can instruct using cache headers that every browser support. That usually reduces heavy hitters by a lot, even if you set the browser TTL to 1 minute which is fine for most of the scenarios.
[0] https://symfony.com/bundles/ux-live-component/current/index....
There isn't an official "protocol" so I had to figure it out by watching the WS traffic and determining how it worked which was fun if not tedious. That said, the more I learned, the more I was impressed by the efficiency and the programming model which felt simpler yet more powerful than SPAs.
I did get to a point where I just got too busy to keep up and over the last couple of years things have changed a bit on the "protocol" side.
But recently (a week ago-ish), I started poking at the old LiveViewJS repo with the help of coding agents. Now that Phoenix is past 1.0 and the JS runtimes (Node, Deno, Bun) have more overlap in terms of APIs and library support, I think it will be more straight forward and frankly easier to get and stay at parity.
What’s right with the idea, really? It’s exactly what the tried and true preferences of developers have been shown to be: getting in the way of the happy path for no reason.
Now you can have build steps and put story points in Jira and do it all on the server where we don’t have to see it, and the success condition is that the text gets served. Both sides can be happy now.
Overhead, Security, Denial of service to name a few.
You now have two states to track. Is the web-server serving the current version that the web socket is rendering?
Is your monitoring enough? Is your monitoring going to detect if the web-socket server is suddenly taken offline? How do you monitor your web server is alive and ready to serve requests in the time of need?
How do you determine if the socket server is actual offline and not frazzled itself in an event-loop? A stray network packet you never conditioned it for.
If both your web-socket server and the web-server are going to follow the same source of truth for fail-over why not just use the web-server?
The web-server is a tried and true method of serving websites. An application that allows you to easily load balance; tune and enhance with other security features. The best part is than you can actually serve a website without requiring JavaScript.
Enterprise/corporate/country DPI firewalls like to silently block web sockets; any requests you're going to be rendering blank back to the client. Determining if the client is blocked isn't easy and how do you let the clients report an issue if they can't render the support page?
The starting sequence of a web socket is an HTTP request header to an upgrade the connection. Correctly configured DPI firewalls block these upgrade headers so for all you know the connection has been made but the renderer fails silently.
You still need a service to serve the JavaScript fronted so unless you create a WebSocket HTTP server which you've then opened a can of worms; you have a perfectly functional web-server sitting around idly wasting resources.
As I bombard your web-socket server with faux requests slowloris style. Your web-server is alive and as far as it knows your socket server is alive too, how do you determine if the web socket is actually under attack? This adds more complexity in the mix.
It's not wrong per-se. For a infrastructure learning exercise sure. However for anything else it's a waste of time and will cause headaches. The resources and the overhead for it all just isn't worth it. It's a mirage of something that looks opportunistic but isn't.
Furthermore any alterations need testing on both parts. If you were to apply a hotfix for the web-socket side, does this negatively effect the web-server side?
Does it perform the same way in Firefox and Chrome? If Firefox is slower at parsing the JavaScript html json, how are you going to accommodate that?
Until someone bombs your websocket server and you then have nothing at all.
Just make a normal website!! You've invented an MPA with extra steps!
A common use case: eg in Rails, a user has a table open. you can stream new records to the top of that table as they are created in ~5 lines of ruby (a broadcast on the model, and put the table rows in a turbo_frame with a turbo_stream_from somewhere on the page).
There are real limits to this -- you have to hold the update dependency graph in your head -- but the benefits are huge for small to medium amounts of responsiveness.
My experience has been great with Rails/Turbo and htmx.
The system is called Turbo. A turbo_frame is just a custom html element. You can largely use it instead of a div.
Turbo's js watches for navigation events (link clicks, form submits) that originate inside one of these elements, and instead of letting the browser do a full navigation, it:
1 - makes the request itself, against the usual rails routes. It uses your normal routing, sessions, cookies, etc.
2 - Intercepts the html response and looks for a <turbo-frame id="..."> that matches the id of the frame that triggered the request
3 - Swaps just that element's contents into the page.
more concretely: suppose I have a list of people in a flex table. I wrap the people table in a turbo_frame so I can prepend to it, and wrap each person in a turbo_frame so I can update it. My page can look as so:
etc.If the user edits a form for person 12345, that is wrapped in turbo_frame person_12345.
The browser makes the request itself, grabs the response, pulls out the contents of turbo_frame person_12345 (and NB: the response can be a whole page or just this fragment), then swaps that in for the existing person_12345.
It's designed so you can make your normal MPA with page navigations and reloads for editing a table row or whatever, make a small set of updates to the html, and have this work almost entirely for free. It sounds too good to be true but I've been using it for years and it often really is that easy.
edit: for server-initiated updates, I can broadcast to select listeners:
1 - replace a turbo_frame (person_12345 was updated externally, and I want to just swap out) 2 - prepend (eg for a css table, put my new person_12345 row in front of other rows; 3 - append (same, but at bottom)
I had thought it delivered updated html over sockets, but maybe it was just the data. Did seem to be a bit more of a heavy JS framework, but it's been years.