global server state in server functions [0.7.0-rc.2] #4807

brianmay · 2025-10-17T22:11:25Z

brianmay
Oct 17, 2025

How do I store and retrieve global state, e.g. database handle?

Previously I added an axum extension:

let router = axum::Router::new()
        .serve_dioxus_application(cfg, app)
        .layer(auth_layer)
        .layer(Extension(database));

And I would use the extract() method to get the global value.

But seems 0.7.0-rc.2 no longer has the extract() method.

Instead the new way is to add a parameter to the server function:

(this is from memory, apologizes if I got it wrong)

#[server]
pub async fn get_user(Extension(pool): Extension<DatabasePool>) -> Result<Option<User>, ServerFnError> {
   [...]
}

(actually not 100% sure this is exactly correct, blame chatgpt; I see an example that adds the parameter to the macro not the function)

But this has two limitations:

I have to add/maintain additional parameters to every single server function.
I couldn't work out how to retrieve the session stored with axum-login. I think it may require yet two additional parameters to every server function.

The existing code - which I don't quite understand 100% that deals with axum-login is this:

impl<S: std::marker::Sync + std::marker::Send> axum::extract::FromRequestParts<S> for Session {
    type Rejection = AuthSessionLayerNotFound;

    async fn from_request_parts(
        parts: &mut http::request::Parts,
        state: &S,
    ) -> Result<Self, Self::Rejection> {
        AuthSession::from_request_parts(parts, state)
            .await
            .map(Session)
            .map_err(|_| AuthSessionLayerNotFound)
    }
}

Somehow this makes it so that the extract() function will work on Session values. I am not really clear what the state parameter is.

So chatgpt, always trying to be helpful suggested that I set a task_local! state inside some axum middleware, and use that to replace the missing extract() function. I also have axum middleware that will put the axum-login session in an extension.

use axum::body::Body;
use axum::{
    http::{Request, Response},
    middleware::Next,
};
use dioxus_fullstack::ServerFnError;
use std::sync::Arc;
use thiserror::Error;
use tokio::task_local;

task_local! {
    static REQ_EXTENSIONS: Arc<axum::http::Extensions>;
}

/// Middleware version of `with_request_context`
pub async fn with_request_context(req: Request<Body>, next: Next) -> Response<Body> {
    // Store in task-local, run next without changing the request
    REQ_EXTENSIONS
        .scope(parts_arc.clone(), async move { next.run(req).await })
        .await
}

#[derive(Debug, Error)]
#[error("Requested extension not found")]
pub struct ExtractError;

impl From<ExtractError> for ServerFnError {
    fn from(err: ExtractError) -> Self {
        ServerFnError::new(err.to_string())
    }
}

/// Helper similar to old `extract::<T>()`
pub fn extract<T>() -> Result<T, ExtractError>
where
    T: Clone + Send + Sync + 'static,
{
    REQ_EXTENSIONS
        .try_with(|parts| {
            // Try to extract Extension<T> from request extensions
            parts.get::<T>().cloned().ok_or(ExtractError)
        })
        .map_err(|_| ExtractError)?
}

And add to the axum router above:

        .layer(axum::middleware::from_fn(context::with_request_context))

Problem here is that - to the best of my knowledge - axum middleware is not called for server functions. Or if it is, REQ_EXTENSIONS is not set inside the server functions for some other reason.

So I thought I probably should ask here for help.

brianmay · 2025-10-17T22:25:33Z

brianmay
Oct 17, 2025
Author

chatgpt gave me some suggestions on how to get axum middleware to work with server functions. I didn't include it in the description above though as it appears to be complete nonsense.

If I said anything that appears to be wrong, please feel free to correct me :-)

0 replies

brianmay · 2025-10-18T03:28:59Z

brianmay
Oct 18, 2025
Author

OK, so the middleware does work when calling the server functions manually.

But when calling the server functions from the app, dioxus somehow does it in such a way to bypass the axum middleware. Not sure I understand really.

1 reply

brianmay Oct 18, 2025
Author

Oh, I am forgetting the initial page is rendered on the server, and the server can call the function directly.

oops.

I guess the middleware approach isn't going to work here.

chatgpt is giving me some interesting ideas on how I can replace the ServerFnBackend backend stored in the DioxusServerFnSet object with a wrapper. Unfortunately I think chatgpt is hallucinating. I don't see those names anywhere in the Dioxus code.

brianmay · 2025-10-18T05:41:19Z

brianmay
Oct 18, 2025
Author

I found a FullstackContext. This looks hopeful.

I can call FullstackContext::current() and it returns good data.

I can include a call to FullstackContext::extract, which looks hopeful too.

But the moment I try to await on the future, and this is included in a server function, suddenly rust complains that it can't use the axum Handler trait for the server function.

Doesn't matter if the extract is directly in the server function, or if the server function calls a helper function that calls extract, or if there is any number of nested calls.

This is kind of weird.

I note FullstackContext is based on Rc values, wonder if this is somehow the problem. Async code on Tokio may require Arc.

Unfortunately the extract method is async, so I have to call it from async code.

Oh well, I guess this isn't the solution I hoped it might be.

6 replies

brianmay Oct 18, 2025
Author

Actually, not 100% sure this extract() method will do what I need.

Possibly I can get the axum-login session with this, but maybe not an Axum Extension???

brianmay Oct 18, 2025
Author

Bug filled: #4810

Supposedly I should be able to write the appropriate implementation of FromRequestParts, and then access parts.extensions(). Won't be able to test this until #4810 is fixed.

e.g. something like:

impl<S: std::marker::Sync + std::marker::Send> axum::extract::FromRequestParts<S> for DatabasePool {
    type Rejection = (axum::http::StatusCode, String);

    async fn from_request_parts(
        parts: &mut http::request::Parts,
        _state: &S,
    ) -> Result<Self, Self::Rejection> {
        if let Some(ctx) = parts.extensions.get::<DatabasePool>() {
            Ok(ctx.clone())
        } else {
            Err((
                axum::http::StatusCode::INTERNAL_SERVER_ERROR,
                "DatabasePool not found in Extensions".into(),
            ))
        }
    }
}

This won't work as is because both trait and type are foreign, but hopefully it shows the point.

brianmay Oct 21, 2025
Author

The FullstackContext::extract() method relies on FullstackContext::current() which in turn calls Runtime::try_current(), but this returns None when called from a server function that is remotely called.

Am I even on the right track here?

brianmay Oct 21, 2025
Author

I see 0.7.0-rc.3 was just released, but considering I was on main I think this hasn't been addressed.

brianmay Oct 21, 2025
Author

This is the commit that remove the working extract(): f2b1c6d

Think I will just stay with 0.7.0-rc.0 for now until I can get somebody to talk to me.

Uh oh!

global server state in server functions [0.7.0-rc.2] #4807

Uh oh!

brianmay Oct 17, 2025

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