risingwave_rpc_client/
channel.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::task::{Context, Poll};
16
17use futures::Future;
18use http::HeaderValue;
19use risingwave_common::util::tracing::TracingContext;
20use tonic::body::BoxBody;
21use tower::Service;
22
23/// A service wrapper that hacks the gRPC request and response for observability.
24///
25/// - Inject the [`TracingContext`] obtained from the current tracing span into the HTTP headers of the request.
26///   The server can then extract the [`TracingContext`] from the HTTP headers with the `TracingExtract` middleware.
27///   See also `TracingExtract` in the `common_service` crate.
28///
29/// - Add the path of the request (indicating the gRPC call) to the response headers. The error reporting can then
30///   include the gRPC call name in the message.
31#[derive(Clone, Debug)]
32pub struct WrappedChannel {
33    inner: tonic::transport::Channel,
34}
35
36#[cfg(not(madsim))]
37impl Service<http::Request<BoxBody>> for WrappedChannel {
38    type Error = tonic::transport::Error;
39    type Response = http::Response<BoxBody>;
40
41    type Future = impl Future<Output = Result<Self::Response, Self::Error>>;
42
43    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
44        self.inner.poll_ready(cx)
45    }
46
47    fn call(&mut self, mut req: http::Request<BoxBody>) -> Self::Future {
48        // This is necessary because tonic internally uses `tower::buffer::Buffer`.
49        // See https://github.com/tower-rs/tower/issues/547#issuecomment-767629149
50        // for details on why this is necessary
51        let clone = self.inner.clone();
52        let mut inner = std::mem::replace(&mut self.inner, clone);
53
54        async move {
55            let path = req.uri().path().to_owned();
56
57            let headers = TracingContext::from_current_span().to_http_headers();
58            req.headers_mut().extend(headers);
59
60            let mut response = inner.call(req).await;
61
62            if let Ok(response) = &mut response {
63                if let Ok(path) = HeaderValue::from_str(&path) {
64                    response
65                        .headers_mut()
66                        .insert(risingwave_error::tonic::CALL_KEY, path);
67                }
68            }
69
70            response
71        }
72    }
73}
74
75#[cfg(not(madsim))]
76pub type Channel = WrappedChannel;
77#[cfg(madsim)]
78pub type Channel = tonic::transport::Channel;
79
80/// An extension trait for tonic's `Channel` that wraps it into a [`WrappedChannel`].
81#[easy_ext::ext(WrappedChannelExt)]
82impl tonic::transport::Channel {
83    /// Wraps the channel into a [`WrappedChannel`] for observability.
84    pub fn wrapped(self) -> Channel {
85        #[cfg(not(madsim))]
86        return WrappedChannel { inner: self };
87        #[cfg(madsim)]
88        return self;
89    }
90}
risingwave_rpc_client/channel.rs

risingwave_rpc_client/
channel.rs
