ifyouseewendy/failsafe-rs

A circuit breaker implementation for rust

Failsafe

A circuit breaker implementation which used to detect failures and encapsulates the logic of preventing a failure from constantly recurring, during maintenance, temporary external system failure or unexpected system difficulties.

• https://martinfowler.com/bliki/CircuitBreaker.html
• Read documentation

Features

• Working with both Fn() -> Result and Future.
• Backoff strategies: constant, exponential, equal_jittered, full_jittered
• Failure detection policies: consecutive_failures, success_rate_over_time_window
• Minimum rust version: 1.27

Usage

Add this to your Cargo.toml:

failsafe = "0.2.0"

and this to your crate root:

extern crate failsafe;

Example

Using default backoff strategy and failure accrual policy.

use failsafe::{Config, CircuitBreaker, Error};

// A function that sometimes failed.
fn dangerous_call() -> Result<(), ()> {
  if thread_rng().gen_range(0, 2) == 0 {
    return Err(())
  }
  Ok(())
}

// Create a circuit breaker which configured by reasonable default backoff and
// failure accrual policy.
let circuit_breaker = Config::new().build();

// Call the function in a loop, after some iterations the circuit breaker will
// be in a open state and reject next calls.
for n in 0..100 {
  match circuit_breaker.call(|| dangerous_call()) {
    Err(Error::Inner(_)) => {
      eprintln!("{}: fail", n);
    },
    Err(Error::Rejected) => {
       eprintln!("{}: rejected", n);
       break;
    },
    _ => {}
  }
}

Or configure custom backoff and policy:

use std::time::Duration;
use failsafe::{backoff, failure_policy, CircuitBreaker};

// Create an exponential growth backoff which starts from 10s and ends with 60s.
let backoff = backoff::exponential(Duration::from_secs(10), Duration::from_secs(60));

// Create a policy which failed when three consecutive failures were made.
let policy = failure_policy::consecutive_failures(3, backoff);

// Creates a circuit breaker with given policy.
let circuit_breaker = Config::new()
  .failure_policy(policy)
  .build();