RequestDecompressionLayer on complex layers

[tisonkun]

Summary

https://github.com/GreptimeTeam/greptimedb/blob/a58256d4d3f031470dd765a8cbc849dbbba6863a/src/servers/src/http.rs#L660-L694

Could you add RequestDecompressionLayer to the middleware tower in the code snippet above?

I tried:

            .layer(
                ServiceBuilder::new()
                    .layer(HandleErrorLayer::new(handle_error))
                    .layer(RequestDecompressionLayer::new())
                    .layer(TraceLayer::new_for_http())
                    .layer(TimeoutLayer::new(self.options.timeout))
                    .layer(DefaultBodyLimit::max(
                        self.options
                            .body_limit
                            .0
                            .try_into()
                            .unwrap_or_else(|_| DEFAULT_BODY_LIMIT.as_bytes() as usize),
                    ))
                    .layer(middleware::from_fn_with_state(
                        AuthState::new(self.user_provider.clone()),
                        authorize::check_http_auth,
                    )),
            )

and got:

cargo  build --locked --bin greptime
   Compiling servers v0.8.0 (/Users/tison/GreptimeWorkspace/greptimedb/src/servers)
   Compiling cmd v0.8.0 (/Users/tison/GreptimeWorkspace/greptimedb/src/cmd)
error[E0277]: the trait bound `HandleError<RequestDecompression<tower_http::trace::Trace<tower::timeout::Timeout<axum_core::extract::default_body_limit::private::DefaultBodyLimitService<axum::middleware::FromFn<fn(axum::extract::State<AuthState>, http::Request<_>, axum::middleware::Next<_>) -> impl futures::Future<Output = http::Response<http_body::combinators::box_body::UnsyncBoxBody<bytes::Bytes, axum::Error>>> {check_http_auth::<_>}, AuthState, Route, _>>>, SharedClassifier<ServerErrorsAsFailures>>>, fn(Box<(dyn StdError + std::marker::Send + std::marker::Sync + 'static)>) -> impl futures::Future<Output = axum::Json<HttpResponse>> {handle_error}, _>: tower::Service<http::Request<_>>` is not satisfied
   --> src/servers/src/http.rs:665:17
    |
664 |               .layer(
    |                ----- required by a bound introduced by this call
665 | /                 ServiceBuilder::new()
666 | |                     .layer(HandleErrorLayer::new(handle_error))
667 | |                     .layer(RequestDecompressionLayer::new())
668 | |                     .layer(TraceLayer::new_for_http())
...   |
679 | |                         authorize::check_http_auth,
680 | |                     )),
    | |______________________^ the trait `tower::Service<http::Request<_>>` is not implemented for `HandleError<RequestDecompression<Trace<Timeout<DefaultBodyLimitService<FromFn<fn(State<AuthState>, ..., ...) -> ... {check_http_auth::<...>}, ..., ..., ...>>>, ...>>, ..., ...>`
    |
    = help: the following other types implement trait `tower::Service<Request>`:
              HandleError<S, F, ()>
              HandleError<S, F, (T1, T2)>
              HandleError<S, F, (T1, T2, T3)>
              HandleError<S, F, (T1, T2, T3, T4)>
              HandleError<S, F, (T1, T2, T3, T4, T5)>
              HandleError<S, F, (T1, T2, T3, T4, T5, T6)>
              HandleError<S, F, (T1, T2, T3, T4, T5, T6, T7)>
              HandleError<S, F, (T1, T2, T3, T4, T5, T6, T7, T8)>
            and 9 others
note: the method call chain might not have had the expected associated types
   --> src/servers/src/http.rs:666:22
    |
665 |                   ServiceBuilder::new()
    |                   --------------------- this expression has type `ServiceBuilder<Identity>`
666 |                       .layer(HandleErrorLayer::new(handle_error))
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Layer::Service` is `HandleError<_, fn(Box<dyn Error + Send + Sync>) -> impl Future<Output = Json<HttpResponse>> {handle_error}, _>` here
667 |                       .layer(RequestDecompressionLayer::new())
    |                        --------------------------------------- `Layer::Service` remains `HandleError<RequestDecompression<_>, fn(Box<dyn Error + Send + Sync>) -> impl Future<Output = Json<HttpResponse>> {handle_error}, _>` here
668 |                       .layer(TraceLayer::new_for_http())
...

I tried a lot of other pattern but just lost in the type hell.

axum version

0.6.20

I cannot upgrade due to GreptimeTeam/greptimedb#3610

[tisonkun]

Looks related to the ReqBody type bound, but I don't know how to work it around.

[tisonkun]

cc @jplatte @davidpdrsn

[junderw]

RequestDecompression is the Service of RequestDecompressionLayer.

RequestDecompression only implements Service<Request<_>> when the request body is wrapped in DecompressionBody

Since you're returning a Route that doesn't have any concrete body types associated with it, it treats the body as just a generic type, but since RequestDecompressionLayer's Service only implements Service when there is a concrete wrapper guaranteed around the request body type, this won't compile.

[junderw]

So in this link: https://docs.rs/tower-http/latest/tower_http/decompression/index.html#request

The example does not work and throws the same error when you remove DecompressionBody from the parameter of the handler.

[tisonkun]

Yeah. I know the rationales here now. But does it simply mean that I can't write a compiled program even if the scenario is valid?

[tisonkun]

Or in a positive question: how can I rearrange the code to make it work? Perhaps let's avoid merge all the logic into one big function.

[junderw]

I was able to get some sort of progress with the following:

    pub fn build<B>(&self, router: Router<(), DecompressionBody<B>>) -> Router<(), DecompressionBody<B>>
    where
        B: Body + Send,
        B::Data: Send,
        B::Error: Into<BoxError> + Send,
    {

But now I think some of the handlers you are mixing in (authorize::check_http_auth etc) are not actually using DecompressionBody and so it's erroring.

[junderw]

Anywho, hope this was somewhat of help. Good luck.

[junderw]

I think it might be worth it to move the discussion here: tower-rs/tower-http#491

[ITpandaffm]

this discussion may help: #2549