You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: tracing.rs
    path of file: ./repos/risingwave/src/common/common_service/src
    
    the code of the file until where you have to start completion: // Copyright 2024 RisingWave Labs
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::task::{Context, Poll};

use futures::Future;
use hyper::Body;
use risingwave_common::util::tracing::TracingContext;
use tower::{Layer, Service};
use tracing::Instrument;

/// A layer that decorates the inner service with [`TracingExtract`].
#[derive(Clone, Default)]
pub struct TracingExtractLayer {
    _private: (),
}

    
    fn call(&mut self, req: hyper::Request<Body>) -> Self::Future {
        // This is necessary because tonic internally uses `tower::buffer::Buffer`.
        // See https://github.com/tower-rs/tower/issues/547#issuecomment-767629149
        // for details on why this is necessary
        let clone = self.inner.clone();
        let mut inner = std::mem::replace(&mut self.inner, clone);

        async move {
            let span =
                if let Some(tracing_context) = TracingContext::from_http_headers(req.headers()) {
                    let span = tracing::info_span!(
                        "grpc_serve",
                        "otel.name" = req.uri().path(),
                        uri = %req.uri()
                    );
                    tracing_context.attach(span)
                } else {
                    tracing::Span::none() // if there's no parent span, disable tracing for this request
                };

            inner.call(req).instrument(span).await
        }
    }