Circular dependencies with state

[prabirshrestha]

I have a scenario where I'm hiring circular dependencie issue and wondering what is the best way to solve this.

I have an AuthService which allows me to validate jwt token as well as signin and signout. When I signin or signout I want to send send a notification, but then I want to also validate the jwt token.

let (layer, io) = SocketIo::builder().with_state(AuthService::new()).build_layer();

As you can see I can't pass io to AuthService as it hasn't been created. While I could easily break jwt validation and signin and singout and remove the dependencies, I'm facing similar issues with other states.

Wondering if there is some way to set the state once io has been created this way I can use AuthService state during on_connect and signin and signout can also use io and emit messages.

let (layer, mut io) = SocketIo::builder().build_layer();
io.set_state(AuthService::new(io));

[tausifcreates]

What does the AuthService look like? I would set the io in a global variable after initialization, then I can use it in any route.

[Totodore]

There is no way to set state on SocketIo once it has been initialized for the moment :/. So you have to have a global variable or maybe set the io handle on your auth service after the initialization.

[Totodore]

You could also pass the io struct only when you need to perform the action with your service rather than holding a ref to it. But it depends on your AuthService implementation.

[prabirshrestha]

My AuthService looks something like this.

#[async_trait]
pub trait AuthService: Sync + Send {
    async fn decode_token(&self, token: &str) -> AppResult<DecodedToken>;
    async fn verify_password(&self, username: &str, password: &Secret<String>) -> AppResult<()>;
    async fn change_password_by_username(
        &self,
        username: &str,
        change_password_request: &ChangePasswordRequest,
    ) -> AppResult<()>;

    async fn update_user(&self, id: &str, update_user_request: UpdateUserRequest) -> AppResult<()>;

    /// ..
}

In change_password_by_username and update_user I would like to send notification when the function has been called.

async fn on_connect(socket: SocketRef, auth_service: State<Arc<AuthService>>) {
    let headers = &socket.req_parts().headers;
    let jwt = get_jwt_token_from_header(&headers).unwrap_or_default();
    
    let decoded_token = auth_service.decode_token(jwt).await;
    // ...
}

As you can see auth_service is used to decode token in on_connect but also requires access to io.

I would like to avoid global variables. I was sort of hoping if we could have some way to set a state later in io, such that we state can be of type Option<Arc<AuthService>>.

[tausifcreates]

Hm, can you initialize auth_service with io struct passed down to it, after io is created? That way you will not need a global variable.

From what I see, the AuthService is a collection of auth utils, so it might not need to be a state?

It would be nice if the state could be set afterwards, but for now, you might want to consider the other approaches.

[Totodore]

You could also have a fn set_io that would set it on the AuthService but it would require to put a Rwlock.

But I think the best way is to just have functions that takes a SocketIo ref as argument each time it is needed.

[prabirshrestha]

I went with passing io as arguments to avoid RwLock.

let services = Arc::new(...); // this contains a bunch of services
let (io_layer, io) =  SocketIo::builder().build_layer();
let services = Arc::new(Services::new(io.clone()).await?);
io.ns("/", {
  let services = services.clone();
  |socket: SocketRef| async move { on_connection(socket, services).await }
});

[neckaros]

Thank for the impl exemple. I ended up doing the same thing.

@Totodore would it be possible to have an extractor that give us the SocketIo ?

[Totodore]

It requires some changes in the codebase architecture but it is planned.

[neckaros]

Great and thanks for the great work don on this library!