Epic: Allow Kobweb to work in cases where it doesn't own the server

[bitspittle]

To check off items on this list, they should both be supported AND documented

Static support

These items probably just need files to be exported a certain way

• GCP
• Netlify

Dynamic support

These items probably need logic currently backed into the kobweb/backend codebase refactored out into a shareable JVM library and then implemented per target

• ktor
• Spring Boot

Other

I'm not familar with these technologies at this point so they will require a bit more investigation to categorize / understand properly

• WSGI

---

Original comment:

Feedback from the community: "end to end does provide a better headstart experience. but afaik backend is super complex so integrating it w/ something like spring boot would make it a lot more feasible for many use cases"

[bitspittle]

Note that a "workaround" for people running their own servers is to serve the Kobweb site themselves.

• kobweb export --layout static
• Serve .kobweb/site statically
  • For example, in ktor: https://ktor.io/docs/serving-static-content.html

    routing {
       staticFiles("/", ".kobweb/site")
    }
    

  • Remember, you can configure the export location if you need the files to go somewhere else (configure Kobweb)

[NorbertSandor]

I already use Kobweb on the client side - it is great :)
It would be nice if I could use live reloading support during development but also be able to use my Ktor-based backend which I cannot (and don't want to) replace.

[bitspittle]

@NorbertSandor hey, since you have a real case, I have a question for you. If I allowed you to set up my Kobweb server to act as a proxy for your server, would that work for you?

Getting live reloading to work for your custom server probably won't ever happen (getting it right takes a fair bit of custom code, see here which if you dig in does some fancy classloader tricks and makes some assumptions).

That said, if I add proxy support to Kobweb servers, you could start up a Kobweb server and ALSO spin up your custom server, and have Kobweb configured to point at it.

If you rebuild / restart your server, then you kind of get a live reloading experience, as the existing Kobweb server will just keep delegating to whatever is running.

[NorbertSandor]

set up my Kobweb server to act as a proxy for your server

This is how I currently use the Webpack Devserver:

• the Webpack-generated JS files are served directly by the Devserver
• everything else (resources, HTTP endpoints, WebSocket endpoints) is served by my own Ktor backend, proxyied by the Devserver

So currently my Kotlin/JS webapp communicates directly only with the Devserver.
It means I currently spin up 2 servers during development - and I have no problem with it :).

live reloading to work for your custom server probably won't ever happen

I see...
The reason I want to give a try to Kobweb (besides that I already use the Modifier-system and other lower-level features) is that I'm not satisfied with how the Kotlin - Webpack Devserver integration works (or often not works in my case).
I have already tried the generated "hello-world" Kobweb project but I want to try somehow how it would work with my complex multi-project application.

That said, if I add proxy support to Kobweb servers, you could start up a Kobweb server and ALSO spin up your custom server

This is exactly how I currently use the Webpack Devserver.
It proxies everything to my backend except the generated JS files.
So yes, it would probably work.

Just one question: wouldn't it be really big work to implement a HTTP+WS proxy from stratch?
Or do you know a (Ktor-based) ready-to-integrate alternative?

Another idea has just popped in my head, namely to avoid HTTP/WS proxying entirely:

1. I could refactor my Kotlin/JS webapp to call my backend directly instead of letting the Webpack Devserver to proxy my connections.
2. Then I will try to convert the webapp to Kobweb (and replace Webpack-related Gradle tasks like jsBrowserDevelopmentRun with Kobweb tasks).

If I allowed you to set up my Kobweb server to act as a proxy for your server

The reason I don't want you to implement this proxying functionality right now is because I'm not sure that I can successfully convert my app to Kobweb, and I don't want you to work unnecessarily. It is because my biggest problem is not the proxying: my webapp owns the entire application logic, starting from a suspend main() function (it starts a DI container, makes various initializations, etc.), so it will be probably non-trivial to convert it to Kobweb - I don't know if I can do it at all :( (so currently I'm just collecting information about all related tasks, before even starting this huge refactoring).

But thanks for the insights, and giving me the above idea :)

[EchoEllet]

If using Ktor, you should also install the IgnoreTrailingSlash plugin so that your web server will serve index.html when a user visits a directory (e.g. /docs/) instead of returning a 404

Installing IgnoreTrailingSlash didn't fix this issue in my case.

I needed to use File extensions fallbacks:

staticFiles("/", FilePaths.StaticSite.getPath().toFile()) {
  extensions("html")
}

Another unrelated issue

I ended up hosting the static site using kobweb run --env prod --layout static (which delegates to gradlew kobwebStart -PkobwebEnv=PROD -PkobwebRunLayout=STATIC --stacktrace) and running the Ktor server with a different port on the same Linux VPS server.

I think there is a delay in executing the JS code even on localhost:

KobwebStaticSiteOnKtorServerIssue.mov

I didn't experience this issue with kobweb run --env prod --layout static. I didn't investigate further.

EDIT: It seems this issue is reproduced even with kobweb run --env prod --layout static, I can only reproduce it in production mode, is it possible that the generated index.html is being loaded first and then the Kobweb site on production?

I'm also able to reproduce this issue with the default app template.

KobwebDefaultApptemplate.mov

BTW, huge thanks for developing the amazing docs page!

[bitspittle]

I'm surprised you were having trouble with the ktor code as I was using it for a while. But I did notice one case that it failed to work was if you had a folder AND an HTML file with the same name, just in case that's what was happening to you

Current Kobweb routing code is now manually handled, and you can copy if from here if you'd like:

kobweb/backend/server/src/main/kotlin/com/varabyte/kobweb/server/plugins/Routing.kt

Line 660 in 12e1753

private fun Application.configureStaticProdRouting(conf: KobwebConf) {

[EchoEllet]

The solution was straightforward, I filed an issue with a PR, see varabyte/kobweb-site#27. Maybe this wasn't an issue with Ktor 2 and that info was tested and written at that time?

I'm surprised you were having trouble with the ktor code as I was using it for a while

I also served the Kobweb static site previously, and I haven't encountered any issues.

Getting live reloading to work for your custom server probably won't ever happen

BTW Ktor server auto-reload works well too, not as good as Kobweb but it's faster if you rebuild the project using the IDE instead of Gradle continuous build task.