reqwest_connect_rpc/
client.rs

1// Copyright 2025 Anapaya Systems
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//! Connect-RPC client library using reqwest.
15
16use std::{borrow::Cow, sync::Arc, time::Duration};
17
18use bytes::Bytes;
19use reqwest::header::{self, HeaderMap, HeaderValue};
20use thiserror::Error;
21use tracing::Instrument;
22
23use crate::{
24    error::CrpcError,
25    token_source::{TokenSource, TokenSourceError},
26};
27
28/// Connect RPC client error.
29#[derive(Debug, Error)]
30pub enum CrpcClientError {
31    /// Error that occurs when there is a connection issue.
32    #[error("connection error {context}: {source:#?}")]
33    ConnectionError {
34        /// Additional context about the connection error.
35        context: Cow<'static, str>,
36        /// The underlying source error.
37        source: Box<dyn std::error::Error + Send + Sync + 'static>,
38    },
39    /// Error returned by the server.
40    #[error("server returned an error: {0:#?}")]
41    CrpcError(CrpcError),
42    /// Error decoding the response body.
43    #[error("failed to decode response body: {context}: {source:#?}")]
44    DecodeError {
45        /// Additional context about the decoding error.
46        context: Cow<'static, str>,
47        /// The underlying source error.
48        source: Option<Box<dyn std::error::Error + Send + Sync + 'static>>,
49        /// The response body, if available.
50        body: Option<Bytes>,
51    },
52    /// Error retrieving a token from the token source.
53    #[error("failed to retrieve token: {0}")]
54    TokenSourceError(#[from] TokenSourceError),
55    /// The token cannot be sent as an `Authorization` header value.
56    #[error("failed to format token as header value: {0}")]
57    InvalidTokenHeader(#[source] header::InvalidHeaderValue),
58}
59
60impl CrpcClientError {
61    /// Returns whether the failure is transient, so that a retry may help.
62    ///
63    /// Prefer this over matching the variants: a new variant would silently fall into a caller's
64    /// wildcard arm.
65    #[must_use]
66    pub fn is_transient(&self) -> bool {
67        match self {
68            // The exchange did not complete: name resolution failed, the host has no route to
69            // the server, or the connection dropped part way through the response body.
70            Self::ConnectionError { .. } => true,
71            Self::CrpcError(error) => error.is_transient(),
72            Self::DecodeError { .. } => false,
73            Self::InvalidTokenHeader(_) => false,
74            Self::TokenSourceError(error) => error.is_transient(),
75        }
76    }
77}
78
79/// Error creating a [`CrpcClient`].
80#[derive(Debug, Error)]
81pub enum CrpcClientCreationError {
82    /// The HTTP client could not be built.
83    #[error("failed to build HTTP client")]
84    HttpClient(#[source] reqwest::Error),
85    /// The user agent cannot be sent as a `User-Agent` header value.
86    #[error("invalid user agent {user_agent:?}")]
87    InvalidUserAgent {
88        /// The rejected user agent.
89        user_agent: String,
90        /// The underlying cause.
91        #[source]
92        source: header::InvalidHeaderValue,
93    },
94}
95
96impl CrpcClientCreationError {
97    /// Returns whether the failure is transient, so that a retry may help.
98    ///
99    /// Prefer this over matching the variants: a new variant would silently fall into a caller's
100    /// wildcard arm.
101    #[must_use]
102    pub fn is_transient(&self) -> bool {
103        match self {
104            // Creating a client builds a TLS backend and formats a header value from arguments the
105            // caller supplies, so the next attempt with the same arguments fails the same way.
106            Self::HttpClient(_) | Self::InvalidUserAgent { .. } => false,
107        }
108    }
109}
110
111const APPLICATION_PROTO: &str = "application/proto";
112
113/// A Connect-RPC client.
114pub struct CrpcClient {
115    http_client: reqwest::Client,
116    base_url: url::Url,
117    token_source: Option<Arc<dyn TokenSource>>,
118    user_agent: HeaderValue,
119}
120
121impl CrpcClient {
122    /// Creates a new [`CrpcClient`] for the given base URL.
123    pub fn new(base_url: &url::Url) -> Result<Self, CrpcClientCreationError> {
124        let http_client = reqwest::ClientBuilder::new()
125            .timeout(Duration::from_secs(30))
126            .build()
127            .map_err(CrpcClientCreationError::HttpClient)?;
128
129        Self::new_with_client(base_url, http_client)
130    }
131
132    /// Creates a new [`CrpcClient`] for the given base URL and explicit [`reqwest::Client`].
133    pub fn new_with_client(
134        base_url: &url::Url,
135        http_client: reqwest::Client,
136    ) -> Result<Self, CrpcClientCreationError> {
137        let default_user_agent = format!("reqwest-crpc {}", env!("CARGO_PKG_VERSION"));
138        let user_agent = HeaderValue::from_str(&default_user_agent).map_err(|source| {
139            CrpcClientCreationError::InvalidUserAgent {
140                user_agent: default_user_agent,
141                source,
142            }
143        })?;
144
145        Ok(CrpcClient {
146            http_client,
147            base_url: base_url.clone(),
148            token_source: None,
149            user_agent,
150        })
151    }
152
153    /// Uses given token source for authentication of all following requests.
154    pub fn use_token_source(&mut self, token_source: Arc<dyn TokenSource>) -> &mut Self {
155        self.token_source = Some(token_source);
156        self
157    }
158
159    /// Sets the user agent header for all following requests.
160    pub fn use_user_agent(
161        &mut self,
162        user_agent: &str,
163    ) -> Result<&mut Self, CrpcClientCreationError> {
164        self.user_agent = HeaderValue::from_str(user_agent).map_err(|source| {
165            CrpcClientCreationError::InvalidUserAgent {
166                user_agent: user_agent.to_owned(),
167                source,
168            }
169        })?;
170        Ok(self)
171    }
172
173    /// Unary RPC request.
174    pub async fn unary_request<Req, Res>(
175        &self,
176        path: &str,
177        req: &Req,
178    ) -> Result<Res, CrpcClientError>
179    where
180        Req: prost::Message,
181        Res: prost::Message + Default,
182    {
183        self.do_unary_request(path, req)
184            .instrument(tracing::info_span!("request", %path, id = rand::random::<u16>()))
185            .await
186    }
187
188    /// Sends a unary request to the endhost API.
189    async fn do_unary_request<Req, Res>(
190        &self,
191        path: &str,
192        req: &Req,
193    ) -> Result<Res, CrpcClientError>
194    where
195        Req: prost::Message,
196        Res: prost::Message + Default,
197    {
198        let url = self.base_url.join(path).map_err(|e| {
199            CrpcClientError::ConnectionError {
200                context: "error joining base URL and path".into(),
201                source: e.into(),
202            }
203        })?;
204
205        let mut headers = HeaderMap::with_capacity(3);
206        headers.insert(
207            header::CONTENT_TYPE,
208            header::HeaderValue::from_static(APPLICATION_PROTO),
209        );
210        headers.insert(header::USER_AGENT, self.user_agent.clone());
211
212        tracing::trace!(?url, ?headers, "Sending crpc unary request");
213
214        if let Some(token_source) = &self.token_source {
215            let token = token_source.get_token().await?;
216            let token_header = header::HeaderValue::from_str(&token_source.format_header(token))
217                .map_err(CrpcClientError::InvalidTokenHeader)?;
218
219            headers.insert(header::AUTHORIZATION, token_header);
220        }
221
222        let body = req.encode_to_vec();
223        let response = self
224            .http_client
225            .post(url)
226            .body(reqwest::Body::from(body))
227            .headers(headers)
228            .send()
229            .await
230            .map_err(|e| {
231                CrpcClientError::ConnectionError {
232                    context: "error sending request".into(),
233                    source: e.into(),
234                }
235            })?;
236
237        tracing::trace!(status=%response.status(), body_len=%response.content_length().unwrap_or(0), "Received crpc unary response");
238
239        let status = response.status();
240        if !status.is_success() {
241            let response_raw = response
242                .text()
243                .await
244                .unwrap_or_else(|_| "<failed to read body>".to_string());
245
246            // Try to parse the body as a CrpcError, otherwise create a generic one.
247            match serde_json::from_str::<CrpcError>(&response_raw) {
248                Ok(crpc_err) => {
249                    return Err(CrpcClientError::CrpcError(crpc_err));
250                }
251                Err(_) => {
252                    return Err(CrpcClientError::CrpcError(CrpcError::new(
253                        status.into(),
254                        response_raw,
255                    )));
256                }
257            }
258        }
259
260        let body = response.bytes().await.map_err(|e| {
261            CrpcClientError::ConnectionError {
262                context: "error reading response body".into(),
263                source: e.into(),
264            }
265        })?;
266
267        Res::decode(&body[..]).map_err(|e| {
268            CrpcClientError::DecodeError {
269                context: "error decoding response body".into(),
270                source: Some(e.into()),
271                body: Some(body.clone()),
272            }
273        })
274    }
275}
reqwest_connect_rpc/client.rs

reqwest_connect_rpc/
client.rs
