aws_smithy_types/retry.rs
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/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0
*/
//! This module defines types that describe when to retry given a response.
use crate::config_bag::{Storable, StoreReplace};
use std::fmt;
use std::str::FromStr;
use std::time::Duration;
const VALID_RETRY_MODES: &[RetryMode] = &[RetryMode::Standard];
/// Type of error that occurred when making a request.
#[derive(Clone, Copy, Eq, PartialEq, Debug)]
#[non_exhaustive]
pub enum ErrorKind {
/// A connection-level error.
///
/// A `TransientError` can represent conditions such as socket timeouts, socket connection errors, or TLS negotiation timeouts.
///
/// `TransientError` is not modeled by Smithy and is instead determined through client-specific heuristics and response status codes.
///
/// Typically these should never be applied for non-idempotent request types
/// since in this scenario, it's impossible to know whether the operation had
/// a side effect on the server.
///
/// TransientErrors are not currently modeled. They are determined based on specific provider
/// level errors & response status code.
TransientError,
/// An error where the server explicitly told the client to back off, such as a 429 or 503 HTTP error.
ThrottlingError,
/// Server error that isn't explicitly throttling but is considered by the client
/// to be something that should be retried.
ServerError,
/// Doesn't count against any budgets. This could be something like a 401 challenge in Http.
ClientError,
}
impl fmt::Display for ErrorKind {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::TransientError => write!(f, "transient error"),
Self::ThrottlingError => write!(f, "throttling error"),
Self::ServerError => write!(f, "server error"),
Self::ClientError => write!(f, "client error"),
}
}
}
/// Trait that provides an `ErrorKind` and an error code.
pub trait ProvideErrorKind {
/// Returns the `ErrorKind` when the error is modeled as retryable
///
/// If the error kind cannot be determined (e.g. the error is unmodeled at the error kind depends
/// on an HTTP status code, return `None`.
fn retryable_error_kind(&self) -> Option<ErrorKind>;
/// Returns the `code` for this error if one exists
fn code(&self) -> Option<&str>;
}
/// `RetryKind` describes how a request MAY be retried for a given response
///
/// A `RetryKind` describes how a response MAY be retried; it does not mandate retry behavior.
/// The actual retry behavior is at the sole discretion of the RetryStrategy in place.
/// A RetryStrategy may ignore the suggestion for a number of reasons including but not limited to:
/// - Number of retry attempts exceeded
/// - The required retry delay exceeds the maximum backoff configured by the client
/// - No retry tokens are available due to service health
#[non_exhaustive]
#[derive(Eq, PartialEq, Debug)]
pub enum RetryKind {
/// Retry the associated request due to a known `ErrorKind`.
Error(ErrorKind),
/// An Explicit retry (e.g. from `x-amz-retry-after`).
///
/// Note: The specified `Duration` is considered a suggestion and may be replaced or ignored.
Explicit(Duration),
/// The response was a failure that should _not_ be retried.
UnretryableFailure,
/// The response was successful, so no retry is necessary.
Unnecessary,
}
/// Specifies how failed requests should be retried.
#[non_exhaustive]
#[derive(Eq, PartialEq, Debug, Clone, Copy)]
pub enum RetryMode {
/// The standard set of retry rules across AWS SDKs. This mode includes a standard set of errors
/// that are retried, and support for retry quotas. The default maximum number of attempts
/// with this mode is three, unless otherwise explicitly configured with [`RetryConfig`].
Standard,
/// An experimental retry mode that includes the functionality of standard mode but includes
/// automatic client-side throttling. Because this mode is experimental, it might change
/// behavior in the future.
Adaptive,
}
impl FromStr for RetryMode {
type Err = RetryModeParseError;
fn from_str(string: &str) -> Result<Self, Self::Err> {
let string = string.trim();
// eq_ignore_ascii_case is OK here because the only strings we need to check for are ASCII
if string.eq_ignore_ascii_case("standard") {
Ok(RetryMode::Standard)
} else if string.eq_ignore_ascii_case("adaptive") {
Ok(RetryMode::Adaptive)
} else {
Err(RetryModeParseError::new(string))
}
}
}
/// Failure to parse a `RetryMode` from string.
#[derive(Debug)]
pub struct RetryModeParseError {
message: String,
}
impl RetryModeParseError {
pub(super) fn new(message: impl Into<String>) -> Self {
Self {
message: message.into(),
}
}
}
impl fmt::Display for RetryModeParseError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(
f,
"error parsing string '{}' as RetryMode, valid options are: {:#?}",
self.message, VALID_RETRY_MODES
)
}
}
impl std::error::Error for RetryModeParseError {}
/// Builder for [`RetryConfig`].
#[non_exhaustive]
#[derive(Debug, Default, Clone, PartialEq)]
pub struct RetryConfigBuilder {
mode: Option<RetryMode>,
max_attempts: Option<u32>,
initial_backoff: Option<Duration>,
max_backoff: Option<Duration>,
reconnect_mode: Option<ReconnectMode>,
}
impl RetryConfigBuilder {
/// Creates a new builder.
pub fn new() -> Self {
Default::default()
}
/// Sets the retry mode.
pub fn set_mode(&mut self, retry_mode: Option<RetryMode>) -> &mut Self {
self.mode = retry_mode;
self
}
/// Sets the retry mode.
pub fn mode(mut self, mode: RetryMode) -> Self {
self.set_mode(Some(mode));
self
}
/// Set the [`ReconnectMode`] for the retry strategy
///
/// By default, when a transient error is encountered, the connection in use will be poisoned.
/// This prevents reusing a connection to a potentially bad host but may increase the load on
/// the server.
///
/// This behavior can be disabled by setting [`ReconnectMode::ReuseAllConnections`] instead.
pub fn reconnect_mode(mut self, reconnect_mode: ReconnectMode) -> Self {
self.set_reconnect_mode(Some(reconnect_mode));
self
}
/// Set the [`ReconnectMode`] for the retry strategy
///
/// By default, when a transient error is encountered, the connection in use will be poisoned.
/// This prevents reusing a connection to a potentially bad host but may increase the load on
/// the server.
///
/// This behavior can be disabled by setting [`ReconnectMode::ReuseAllConnections`] instead.
pub fn set_reconnect_mode(&mut self, reconnect_mode: Option<ReconnectMode>) -> &mut Self {
self.reconnect_mode = reconnect_mode;
self
}
/// Sets the max attempts. This value must be greater than zero.
pub fn set_max_attempts(&mut self, max_attempts: Option<u32>) -> &mut Self {
self.max_attempts = max_attempts;
self
}
/// Sets the max attempts. This value must be greater than zero.
pub fn max_attempts(mut self, max_attempts: u32) -> Self {
self.set_max_attempts(Some(max_attempts));
self
}
/// Set the initial_backoff duration. This duration should be non-zero.
pub fn set_initial_backoff(&mut self, initial_backoff: Option<Duration>) -> &mut Self {
self.initial_backoff = initial_backoff;
self
}
/// Set the initial_backoff duration. This duration should be non-zero.
pub fn initial_backoff(mut self, initial_backoff: Duration) -> Self {
self.set_initial_backoff(Some(initial_backoff));
self
}
/// Set the max_backoff duration. This duration should be non-zero.
pub fn set_max_backoff(&mut self, max_backoff: Option<Duration>) -> &mut Self {
self.max_backoff = max_backoff;
self
}
/// Set the max_backoff duration. This duration should be non-zero.
pub fn max_backoff(mut self, max_backoff: Duration) -> Self {
self.set_max_backoff(Some(max_backoff));
self
}
/// Merge two builders together. Values from `other` will only be used as a fallback for values
/// from `self` Useful for merging configs from different sources together when you want to
/// handle "precedence" per value instead of at the config level
///
/// # Example
///
/// ```rust
/// # use aws_smithy_types::retry::{RetryMode, RetryConfigBuilder};
/// let a = RetryConfigBuilder::new().max_attempts(1);
/// let b = RetryConfigBuilder::new().max_attempts(5).mode(RetryMode::Adaptive);
/// let retry_config = a.take_unset_from(b).build();
/// // A's value take precedence over B's value
/// assert_eq!(retry_config.max_attempts(), 1);
/// // A never set a retry mode so B's value was used
/// assert_eq!(retry_config.mode(), RetryMode::Adaptive);
/// ```
pub fn take_unset_from(self, other: Self) -> Self {
Self {
mode: self.mode.or(other.mode),
max_attempts: self.max_attempts.or(other.max_attempts),
initial_backoff: self.initial_backoff.or(other.initial_backoff),
max_backoff: self.max_backoff.or(other.max_backoff),
reconnect_mode: self.reconnect_mode.or(other.reconnect_mode),
}
}
/// Builds a `RetryConfig`.
pub fn build(self) -> RetryConfig {
RetryConfig {
mode: self.mode.unwrap_or(RetryMode::Standard),
max_attempts: self.max_attempts.unwrap_or(3),
initial_backoff: self
.initial_backoff
.unwrap_or_else(|| Duration::from_secs(1)),
reconnect_mode: self
.reconnect_mode
.unwrap_or(ReconnectMode::ReconnectOnTransientError),
max_backoff: self.max_backoff.unwrap_or_else(|| Duration::from_secs(20)),
use_static_exponential_base: false,
}
}
}
/// Retry configuration for requests.
#[non_exhaustive]
#[derive(Debug, Clone, PartialEq)]
pub struct RetryConfig {
mode: RetryMode,
max_attempts: u32,
initial_backoff: Duration,
max_backoff: Duration,
reconnect_mode: ReconnectMode,
use_static_exponential_base: bool,
}
impl Storable for RetryConfig {
type Storer = StoreReplace<RetryConfig>;
}
/// Mode for connection re-establishment
///
/// By default, when a transient error is encountered, the connection in use will be poisoned. This
/// behavior can be disabled by setting [`ReconnectMode::ReuseAllConnections`] instead.
#[derive(Debug, Clone, PartialEq, Copy)]
pub enum ReconnectMode {
/// Reconnect on [`ErrorKind::TransientError`]
ReconnectOnTransientError,
/// Disable reconnect on error
///
/// When this setting is applied, 503s, timeouts, and other transient errors will _not_
/// lead to a new connection being established unless the connection is closed by the remote.
ReuseAllConnections,
}
impl Storable for ReconnectMode {
type Storer = StoreReplace<ReconnectMode>;
}
impl RetryConfig {
/// Creates a default `RetryConfig` with `RetryMode::Standard` and max attempts of three.
pub fn standard() -> Self {
Self {
mode: RetryMode::Standard,
max_attempts: 3,
initial_backoff: Duration::from_secs(1),
reconnect_mode: ReconnectMode::ReconnectOnTransientError,
max_backoff: Duration::from_secs(20),
use_static_exponential_base: false,
}
}
/// Creates a default `RetryConfig` with `RetryMode::Adaptive` and max attempts of three.
pub fn adaptive() -> Self {
Self {
mode: RetryMode::Adaptive,
max_attempts: 3,
initial_backoff: Duration::from_secs(1),
reconnect_mode: ReconnectMode::ReconnectOnTransientError,
max_backoff: Duration::from_secs(20),
use_static_exponential_base: false,
}
}
/// Creates a `RetryConfig` that has retries disabled.
pub fn disabled() -> Self {
Self::standard().with_max_attempts(1)
}
/// Set this config's [retry mode](RetryMode).
pub fn with_retry_mode(mut self, retry_mode: RetryMode) -> Self {
self.mode = retry_mode;
self
}
/// Set the maximum number of times a request should be tried, including the initial attempt.
/// This value must be greater than zero.
pub fn with_max_attempts(mut self, max_attempts: u32) -> Self {
self.max_attempts = max_attempts;
self
}
/// Set the [`ReconnectMode`] for the retry strategy
///
/// By default, when a transient error is encountered, the connection in use will be poisoned.
/// This prevents reusing a connection to a potentially bad host but may increase the load on
/// the server.
///
/// This behavior can be disabled by setting [`ReconnectMode::ReuseAllConnections`] instead.
pub fn with_reconnect_mode(mut self, reconnect_mode: ReconnectMode) -> Self {
self.reconnect_mode = reconnect_mode;
self
}
/// Set the multiplier used when calculating backoff times as part of an
/// [exponential backoff with jitter](https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/)
/// strategy. Most services should work fine with the default duration of 1 second, but if you
/// find that your requests are taking too long due to excessive retry backoff, try lowering
/// this value.
///
/// ## Example
///
/// *For a request that gets retried 3 times, when initial_backoff is 1 seconds:*
/// - the first retry will occur after 0 to 1 seconds
/// - the second retry will occur after 0 to 2 seconds
/// - the third retry will occur after 0 to 4 seconds
///
/// *For a request that gets retried 3 times, when initial_backoff is 30 milliseconds:*
/// - the first retry will occur after 0 to 30 milliseconds
/// - the second retry will occur after 0 to 60 milliseconds
/// - the third retry will occur after 0 to 120 milliseconds
pub fn with_initial_backoff(mut self, initial_backoff: Duration) -> Self {
self.initial_backoff = initial_backoff;
self
}
/// Set the maximum backoff time.
pub fn with_max_backoff(mut self, max_backoff: Duration) -> Self {
self.max_backoff = max_backoff;
self
}
/// Hint to the retry strategy whether to use a static exponential base.
///
/// When a retry strategy uses exponential backoff, it calculates a random base. This causes the
/// retry delay to be slightly random, and helps prevent "thundering herd" scenarios. However,
/// it's often useful during testing to know exactly how long the delay will be.
///
/// Therefore, if you're writing a test and asserting an expected retry delay,
/// set this to `true`.
#[cfg(feature = "test-util")]
pub fn with_use_static_exponential_base(mut self, use_static_exponential_base: bool) -> Self {
self.use_static_exponential_base = use_static_exponential_base;
self
}
/// Returns the retry mode.
pub fn mode(&self) -> RetryMode {
self.mode
}
/// Returns the [`ReconnectMode`]
pub fn reconnect_mode(&self) -> ReconnectMode {
self.reconnect_mode
}
/// Returns the max attempts.
pub fn max_attempts(&self) -> u32 {
self.max_attempts
}
/// Returns the backoff multiplier duration.
pub fn initial_backoff(&self) -> Duration {
self.initial_backoff
}
/// Returns the max backoff duration.
pub fn max_backoff(&self) -> Duration {
self.max_backoff
}
/// Returns true if retry is enabled with this config
pub fn has_retry(&self) -> bool {
self.max_attempts > 1
}
/// Returns `true` if retry strategies should use a static exponential base instead of the
/// default random base.
///
/// To set this value, the `test-util` feature must be enabled.
pub fn use_static_exponential_base(&self) -> bool {
self.use_static_exponential_base
}
}
#[cfg(test)]
mod tests {
use crate::retry::{RetryConfigBuilder, RetryMode};
use std::str::FromStr;
#[test]
fn retry_config_builder_merge_with_favors_self_values_over_other_values() {
let self_builder = RetryConfigBuilder::new()
.max_attempts(1)
.mode(RetryMode::Adaptive);
let other_builder = RetryConfigBuilder::new()
.max_attempts(5)
.mode(RetryMode::Standard);
let retry_config = self_builder.take_unset_from(other_builder).build();
assert_eq!(retry_config.max_attempts, 1);
assert_eq!(retry_config.mode, RetryMode::Adaptive);
}
#[test]
fn retry_mode_from_str_parses_valid_strings_regardless_of_casing() {
assert_eq!(
RetryMode::from_str("standard").ok(),
Some(RetryMode::Standard)
);
assert_eq!(
RetryMode::from_str("STANDARD").ok(),
Some(RetryMode::Standard)
);
assert_eq!(
RetryMode::from_str("StAnDaRd").ok(),
Some(RetryMode::Standard)
);
// assert_eq!(
// RetryMode::from_str("adaptive").ok(),
// Some(RetryMode::Adaptive)
// );
// assert_eq!(
// RetryMode::from_str("ADAPTIVE").ok(),
// Some(RetryMode::Adaptive)
// );
// assert_eq!(
// RetryMode::from_str("aDaPtIvE").ok(),
// Some(RetryMode::Adaptive)
// );
}
#[test]
fn retry_mode_from_str_ignores_whitespace_before_and_after() {
assert_eq!(
RetryMode::from_str(" standard ").ok(),
Some(RetryMode::Standard)
);
assert_eq!(
RetryMode::from_str(" STANDARD ").ok(),
Some(RetryMode::Standard)
);
assert_eq!(
RetryMode::from_str(" StAnDaRd ").ok(),
Some(RetryMode::Standard)
);
// assert_eq!(
// RetryMode::from_str(" adaptive ").ok(),
// Some(RetryMode::Adaptive)
// );
// assert_eq!(
// RetryMode::from_str(" ADAPTIVE ").ok(),
// Some(RetryMode::Adaptive)
// );
// assert_eq!(
// RetryMode::from_str(" aDaPtIvE ").ok(),
// Some(RetryMode::Adaptive)
// );
}
#[test]
fn retry_mode_from_str_wont_parse_invalid_strings() {
assert_eq!(RetryMode::from_str("std").ok(), None);
assert_eq!(RetryMode::from_str("aws").ok(), None);
assert_eq!(RetryMode::from_str("s t a n d a r d").ok(), None);
assert_eq!(RetryMode::from_str("a d a p t i v e").ok(), None);
}
}