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Added a way to specify custom functions which decide whether a request should be retried or not (#33)

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* Add a generic function to the middleware struct for the `Retryable` decision.

The generic function can be used to define custom behaviour to decide whether to retry a request or not.

By default, this function is `Retryable::from_reqwest_response` which is the same as it was before.

* Add a way to create custom retry policies.

A RetryStrategy will dictate what decision will be made based on the result of the sent request.

* Add RetryableStrategy in the `RetryTransientMiddleware` struct instead of the seperate functions

* Add constructor to create a `RetryTransientMiddleware` with a custom `RetryableStrategy`

* Run `cargo fmt`

* Add example code to the `RetryableStrategy` struct

* Run `cargo fmt`

* Updated changelog

* use a trait

* docs

* include latest changes

Co-authored-by: Conrad Ludgate <conrad.ludgate@truelayer.com>
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5 changed files with 257 additions and 110 deletions
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3
reqwest-retry/CHANGELOG.md
View file

@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
## [Unreleased] ## [Unreleased]
### Added
- `RetryableStrategy` which allows for custom retry decisions based on the response that a request got
## [0.2.1] - 2022-12-01 ## [0.2.1] - 2022-12-01
@ -12,7 +14,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- Classify `io::Error`s and `hyper::Error(Canceled)` as transient - Classify `io::Error`s and `hyper::Error(Canceled)` as transient
## [0.2.0] - 2022-11-15 ## [0.2.0] - 2022-11-15
### Changed ### Changed
- Updated `reqwest-middleware` to `0.2.0` - Updated `reqwest-middleware` to `0.2.0`

5
reqwest-retry/src/lib.rs
View file

@ -27,8 +27,13 @@
mod middleware; mod middleware;
mod retryable; mod retryable;
mod retryable_strategy;
pub use retry_policies::{policies, RetryPolicy}; pub use retry_policies::{policies, RetryPolicy};
pub use middleware::RetryTransientMiddleware; pub use middleware::RetryTransientMiddleware;
pub use retryable::Retryable; pub use retryable::Retryable;
pub use retryable_strategy::{
default_on_request_failure, default_on_request_success, DefaultRetryableStrategy,
RetryableStrategy,
};

44
reqwest-retry/src/middleware.rs
View file

@ -1,6 +1,6 @@
//! `RetryTransientMiddleware` implements retrying requests on transient errors. //! `RetryTransientMiddleware` implements retrying requests on transient errors.
use crate::retryable_strategy::RetryableStrategy;
use crate::retryable::Retryable; use crate::{retryable::Retryable, retryable_strategy::DefaultRetryableStrategy};
use anyhow::anyhow; use anyhow::anyhow;
use chrono::Utc; use chrono::Utc;
use reqwest::{Request, Response}; use reqwest::{Request, Response};
@ -44,20 +44,42 @@ use task_local_extensions::Extensions;
/// * You can wrap this middleware in a custom one which skips retries for streaming requests. /// * You can wrap this middleware in a custom one which skips retries for streaming requests.
/// * You can write a custom retry middleware that builds new streaming requests from the data /// * You can write a custom retry middleware that builds new streaming requests from the data
/// source directly, avoiding the issue of streaming requests not being clonable. /// source directly, avoiding the issue of streaming requests not being clonable.
pub struct RetryTransientMiddleware<T: RetryPolicy + Send + Sync + 'static> { pub struct RetryTransientMiddleware<
T: RetryPolicy + Send + Sync + 'static,
R: RetryableStrategy + Send + Sync + 'static = DefaultRetryableStrategy,
> {
retry_policy: T, retry_policy: T,
retryable_strategy: R,
} }
impl<T: RetryPolicy + Send + Sync> RetryTransientMiddleware<T> { impl<T: RetryPolicy + Send + Sync> RetryTransientMiddleware<T, DefaultRetryableStrategy> {
/// Construct `RetryTransientMiddleware` with a [retry_policy][retry_policies::RetryPolicy]. /// Construct `RetryTransientMiddleware` with a [retry_policy][RetryPolicy].
pub fn new_with_policy(retry_policy: T) -> Self { pub fn new_with_policy(retry_policy: T) -> Self {
Self { retry_policy } Self::new_with_policy_and_strategy(retry_policy, DefaultRetryableStrategy)
}
}
impl<T, R> RetryTransientMiddleware<T, R>
where
T: RetryPolicy + Send + Sync,
R: RetryableStrategy + Send + Sync,
{
/// Construct `RetryTransientMiddleware` with a [retry_policy][RetryPolicy] and [retryable_strategy](RetryableStrategy).
pub fn new_with_policy_and_strategy(retry_policy: T, retryable_strategy: R) -> Self {
Self {
retry_policy,
retryable_strategy,
}
} }
} }
#[cfg_attr(not(target_arch = "wasm32"), async_trait::async_trait)] #[cfg_attr(not(target_arch = "wasm32"), async_trait::async_trait)]
#[cfg_attr(target_arch = "wasm32", async_trait::async_trait(?Send))] #[cfg_attr(target_arch = "wasm32", async_trait::async_trait(?Send))]
impl<T: RetryPolicy + Send + Sync> Middleware for RetryTransientMiddleware<T> { impl<T, R> Middleware for RetryTransientMiddleware<T, R>
where
T: RetryPolicy + Send + Sync,
R: RetryableStrategy + Send + Sync + 'static,
{
async fn handle( async fn handle(
&self, &self,
req: Request, req: Request,
@ -72,7 +94,11 @@ impl<T: RetryPolicy + Send + Sync> Middleware for RetryTransientMiddleware<T> {
} }
} }
impl<T: RetryPolicy + Send + Sync> RetryTransientMiddleware<T> { impl<T, R> RetryTransientMiddleware<T, R>
where
T: RetryPolicy + Send + Sync,
R: RetryableStrategy + Send + Sync,
{
/// This function will try to execute the request, if it fails /// This function will try to execute the request, if it fails
/// with an error classified as transient it will call itself /// with an error classified as transient it will call itself
/// to retry the request. /// to retry the request.
@ -98,7 +124,7 @@ impl<T: RetryPolicy + Send + Sync> RetryTransientMiddleware<T> {
// We classify the response which will return None if not // We classify the response which will return None if not
// errors were returned. // errors were returned.
break match Retryable::from_reqwest_response(&result) { break match self.retryable_strategy.handle(&result) {
Some(Retryable::Transient) => { Some(Retryable::Transient) => {
// If the response failed and the error type was transient // If the response failed and the error type was transient
// we can safely try to retry the request. // we can safely try to retry the request.

102
reqwest-retry/src/retryable.rs
View file

@ -1,4 +1,4 @@
use http::StatusCode; use crate::retryable_strategy::{DefaultRetryableStrategy, RetryableStrategy};
use reqwest_middleware::Error; use reqwest_middleware::Error;
/// Classification of an error/status returned by request. /// Classification of an error/status returned by request.
@ -16,78 +16,7 @@ impl Retryable {
/// Returns `None` if the response object does not contain any errors. /// Returns `None` if the response object does not contain any errors.
/// ///
pub fn from_reqwest_response(res: &Result<reqwest::Response, Error>) -> Option<Self> { pub fn from_reqwest_response(res: &Result<reqwest::Response, Error>) -> Option<Self> {
match res { DefaultRetryableStrategy.handle(res)
Ok(success) => {
let status = success.status();
if status.is_server_error() {
Some(Retryable::Transient)
} else if status.is_client_error()
&& status != StatusCode::REQUEST_TIMEOUT
&& status != StatusCode::TOO_MANY_REQUESTS
{
Some(Retryable::Fatal)
} else if status.is_success() {
None
} else if status == StatusCode::REQUEST_TIMEOUT
|| status == StatusCode::TOO_MANY_REQUESTS
{
Some(Retryable::Transient)
} else {
Some(Retryable::Fatal)
}
}
Err(error) => match error {
// If something fails in the middleware we're screwed.
Error::Middleware(_) => Some(Retryable::Fatal),
Error::Reqwest(error) => {
#[cfg(not(target_arch = "wasm32"))]
let is_connect = error.is_connect();
#[cfg(target_arch = "wasm32")]
let is_connect = false;
if error.is_timeout() || is_connect {
Some(Retryable::Transient)
} else if error.is_body()
|| error.is_decode()
|| error.is_builder()
|| error.is_redirect()
{
Some(Retryable::Fatal)
} else if error.is_request() {
// It seems that hyper::Error(IncompleteMessage) is not correctly handled by reqwest.
// Here we check if the Reqwest error was originated by hyper and map it consistently.
#[cfg(not(target_arch = "wasm32"))]
if let Some(hyper_error) = get_source_error_type::<hyper::Error>(&error) {
// The hyper::Error(IncompleteMessage) is raised if the HTTP response is well formatted but does not contain all the bytes.
// This can happen when the server has started sending back the response but the connection is cut halfway thorugh.
// We can safely retry the call, hence marking this error as [`Retryable::Transient`].
// Instead hyper::Error(Canceled) is raised when the connection is
// gracefully closed on the server side.
if hyper_error.is_incomplete_message() || hyper_error.is_canceled() {
Some(Retryable::Transient)
// Try and downcast the hyper error to io::Error if that is the
// underlying error, and try and classify it.
} else if let Some(io_error) =
get_source_error_type::<std::io::Error>(hyper_error)
{
Some(classify_io_error(io_error))
} else {
Some(Retryable::Fatal)
}
} else {
Some(Retryable::Fatal)
}
#[cfg(target_arch = "wasm32")]
Some(Retryable::Fatal)
} else {
// We omit checking if error.is_status() since we check that already.
// However, if Response::error_for_status is used the status will still
// remain in the response object.
None
}
}
},
}
} }
} }
@ -96,30 +25,3 @@ impl From<&reqwest::Error> for Retryable {
Retryable::Transient Retryable::Transient
} }
} }
#[cfg(not(target_arch = "wasm32"))]
fn classify_io_error(error: &std::io::Error) -> Retryable {
match error.kind() {
std::io::ErrorKind::ConnectionReset | std::io::ErrorKind::ConnectionAborted => {
Retryable::Transient
}
_ => Retryable::Fatal,
}
}
/// Downcasts the given err source into T.
#[cfg(not(target_arch = "wasm32"))]
fn get_source_error_type<T: std::error::Error + 'static>(
err: &dyn std::error::Error,
) -> Option<&T> {
let mut source = err.source();
while let Some(err) = source {
if let Some(hyper_err) = err.downcast_ref::<T>() {
return Some(hyper_err);
}
source = err.source();
}
None
}

213
reqwest-retry/src/retryable_strategy.rs Normal file
View file

@ -0,0 +1,213 @@
use crate::retryable::Retryable;
use http::StatusCode;
use reqwest_middleware::Error;
/// A strategy to create a [`Retryable`] from a [`Result<reqwest::Response, reqwest_middleware::Error>`]
///
/// A [`RetryableStrategy`] has a single `handler` functions.
/// The result of calling the request could be:
/// - [`reqwest::Response`] In case the request has been sent and received correctly
/// This could however still mean that the server responded with a erroneous response.
/// For example a HTTP statuscode of 500
/// - [`reqwest_middleware::Error`] In this case the request actually failed.
/// This could, for example, be caused by a timeout on the connection.
///
/// Example:
///
/// ```
/// use reqwest_retry::{default_on_request_failure, policies::ExponentialBackoff, Retryable, RetryableStrategy, RetryTransientMiddleware};
/// use reqwest::{Request, Response};
/// use reqwest_middleware::{ClientBuilder, Middleware, Next, Result};
/// use task_local_extensions::Extensions;
///
/// // Log each request to show that the requests will be retried
/// struct LoggingMiddleware;
///
/// #[async_trait::async_trait]
/// impl Middleware for LoggingMiddleware {
/// async fn handle(
/// &self,
/// req: Request,
/// extensions: &mut Extensions,
/// next: Next<'_>,
/// ) -> Result<Response> {
/// println!("Request started {}", req.url());
/// let res = next.run(req, extensions).await;
/// println!("Request finished");
/// res
/// }
/// }
///
/// // Just a toy example, retry when the successful response code is 201, else do nothing.
/// struct Retry201;
/// impl RetryableStrategy for Retry201 {
/// fn handle(&self, res: &Result<reqwest::Response>) -> Option<Retryable> {
/// match res {
/// // retry if 201
/// Ok(success) if success.status() == 201 => Some(Retryable::Transient),
/// // otherwise do not retry a successful request
/// Ok(success) => None,
/// // but maybe retry a request failure
/// Err(error) => default_on_request_failure(error),
/// }
/// }
/// }
///
/// #[tokio::main]
/// async fn main() {
/// // Exponential backoff with max 2 retries
/// let retry_policy = ExponentialBackoff::builder()
/// .build_with_max_retries(2);
///
/// // Create the actual middleware, with the exponential backoff and custom retry stategy.
/// let ret_s = RetryTransientMiddleware::new_with_policy_and_strategy(
/// retry_policy,
/// Retry201,
/// );
///
/// let client = ClientBuilder::new(reqwest::Client::new())
/// // Retry failed requests.
/// .with(ret_s)
/// // Log the requests
/// .with(LoggingMiddleware)
/// .build();
///
/// // Send request which should get a 201 response. So it will be retried
/// let r = client
/// .get("https://httpbin.org/status/201")
/// .send()
/// .await;
/// println!("{:?}", r);
///
/// // Send request which should get a 200 response. So it will not be retried
/// let r = client
/// .get("https://httpbin.org/status/200")
/// .send()
/// .await;
/// println!("{:?}", r);
/// }
/// ```
pub trait RetryableStrategy {
fn handle(&self, res: &Result<reqwest::Response, Error>) -> Option<Retryable>;
}
/// The default [`RetryableStrategy`] for [`RetryTransientMiddleware`](crate::RetryTransientMiddleware).
pub struct DefaultRetryableStrategy;
impl RetryableStrategy for DefaultRetryableStrategy {
fn handle(&self, res: &Result<reqwest::Response, Error>) -> Option<Retryable> {
match res {
Ok(success) => default_on_request_success(success),
Err(error) => default_on_request_failure(error),
}
}
}
/// Default request success retry strategy.
///
/// Will only retry if:
/// * The status was 5XX (server error)
/// * The status was 408 (request timeout) or 429 (too many requests)
///
/// Note that success here means that the request finished without interruption, not that it was logically OK.
pub fn default_on_request_success(success: &reqwest::Response) -> Option<Retryable> {
let status = success.status();
if status.is_server_error() {
Some(Retryable::Transient)
} else if status.is_client_error()
&& status != StatusCode::REQUEST_TIMEOUT
&& status != StatusCode::TOO_MANY_REQUESTS
{
Some(Retryable::Fatal)
} else if status.is_success() {
None
} else if status == StatusCode::REQUEST_TIMEOUT || status == StatusCode::TOO_MANY_REQUESTS {
Some(Retryable::Transient)
} else {
Some(Retryable::Fatal)
}
}
/// Default request failure retry strategy.
///
/// Will only retry if the request failed due to a network error
pub fn default_on_request_failure(error: &Error) -> Option<Retryable> {
match error {
// If something fails in the middleware we're screwed.
Error::Middleware(_) => Some(Retryable::Fatal),
Error::Reqwest(error) => {
#[cfg(not(target_arch = "wasm32"))]
let is_connect = error.is_connect();
#[cfg(target_arch = "wasm32")]
let is_connect = false;
if error.is_timeout() || is_connect {
Some(Retryable::Transient)
} else if error.is_body()
|| error.is_decode()
|| error.is_builder()
|| error.is_redirect()
{
Some(Retryable::Fatal)
} else if error.is_request() {
// It seems that hyper::Error(IncompleteMessage) is not correctly handled by reqwest.
// Here we check if the Reqwest error was originated by hyper and map it consistently.
#[cfg(not(target_arch = "wasm32"))]
if let Some(hyper_error) = get_source_error_type::<hyper::Error>(&error) {
// The hyper::Error(IncompleteMessage) is raised if the HTTP response is well formatted but does not contain all the bytes.
// This can happen when the server has started sending back the response but the connection is cut halfway thorugh.
// We can safely retry the call, hence marking this error as [`Retryable::Transient`].
// Instead hyper::Error(Canceled) is raised when the connection is
// gracefully closed on the server side.
if hyper_error.is_incomplete_message() || hyper_error.is_canceled() {
Some(Retryable::Transient)
// Try and downcast the hyper error to io::Error if that is the
// underlying error, and try and classify it.
} else if let Some(io_error) =
get_source_error_type::<std::io::Error>(hyper_error)
{
Some(classify_io_error(io_error))
} else {
Some(Retryable::Fatal)
}
} else {
Some(Retryable::Fatal)
}
#[cfg(target_arch = "wasm32")]
Some(Retryable::Fatal)
} else {
// We omit checking if error.is_status() since we check that already.
// However, if Response::error_for_status is used the status will still
// remain in the response object.
None
}
}
}
}
#[cfg(not(target_arch = "wasm32"))]
fn classify_io_error(error: &std::io::Error) -> Retryable {
match error.kind() {
std::io::ErrorKind::ConnectionReset | std::io::ErrorKind::ConnectionAborted => {
Retryable::Transient
}
_ => Retryable::Fatal,
}
}
/// Downcasts the given err source into T.
#[cfg(not(target_arch = "wasm32"))]
fn get_source_error_type<T: std::error::Error + 'static>(
err: &dyn std::error::Error,
) -> Option<&T> {
let mut source = err.source();
while let Some(err) = source {
if let Some(err) = err.downcast_ref::<T>() {
return Some(err);
}
source = err.source();
}
None
}