retry: Add generic backoff utilities #685
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This adds a new `Backoff` trait and a `ExponentialBackoff` implementation borrwoed from `linkerd2-proxy`. This provides the initial building blocks for a more fully batteries included retry policy.
seanmonstar
reviewed
Aug 19, 2022
hawkw
reviewed
Aug 19, 2022
tower/src/retry/backoff.rs
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| //! This module contains generic backoff utlities to be used with the retry | ||
| //! layer. | ||
| //! | ||
| //! The [`Backoff`] trait is a generic way to represent backoffs that can use | ||
| //! any timer type. | ||
| //! | ||
| //! [`ExponentialBackoff`] implements [`Backoff`] and provides a batteries | ||
| //! included exponential backoff and jitter strategy. | ||
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| use rand::Rng; | ||
| use rand::{rngs::SmallRng, thread_rng, SeedableRng}; | ||
| use std::fmt::Display; | ||
| use std::future::Future; | ||
| use std::time::Duration; | ||
| use tokio::time; | ||
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the doc comment either for the module or the Backoff trait should probably at least mention what the term "backoff" means, for readers who've never seen it before?
Co-authored-by: Sean McArthur <[email protected]>
Co-authored-by: Eliza Weisman <[email protected]>
Co-authored-by: Eliza Weisman <[email protected]>
LucioFranco
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Aug 23, 2022
This adds new PRNG utilities that only use libstd and not the external `rand` crate. This change's motivation are that in tower middleware that need PRNG don't need the complexity and vast utilities of the `rand` crate. This adds a `Rng` trait which abstracts the simple PRNG features tower needs. This also provides a `HasherRng` which uses the `RandomState` type from libstd to generate random `u64` values. In addition, there is an internal only `sample_inplace` which is used within the balance p2c middleware to randomly pick a ready service. This implementation is crate private since its quite specific to the balance implementation. The goal of this in addition to the balance middlware getting `rand` removed is for the upcoming `Retry` changes. The `next_f64` will be used in the jitter portion of the backoff utilities in #685.
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LucioFranco
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Aug 25, 2022
This adds new PRNG utilities that only use libstd and not the external `rand` crate. This change's motivation are that in tower middleware that need PRNG don't need the complexity and vast utilities of the `rand` crate. This adds a `Rng` trait which abstracts the simple PRNG features tower needs. This also provides a `HasherRng` which uses the `RandomState` type from libstd to generate random `u64` values. In addition, there is an internal only `sample_inplace` which is used within the balance p2c middleware to randomly pick a ready service. This implementation is crate private since its quite specific to the balance implementation. The goal of this in addition to the balance middlware getting `rand` removed is for the upcoming `Retry` changes. The `next_f64` will be used in the jitter portion of the backoff utilities in #685. Co-authored-by: Eliza Weisman <[email protected]>
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I think this is ready for another round of reviews! |
seanmonstar
approved these changes
Aug 30, 2022
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This adds a new
Backofftrait and aExponentialBackoffimplementation borrwoed from
linkerd2-proxy. This provides the initialbuilding blocks for a more fully batteries included retry policy.
cc @rcoh