fabiocicerchia/go-proxy-cache

package circuitbreaker

//                                                                         __
// .-----.-----.______.-----.----.-----.--.--.--.--.______.----.---.-.----|  |--.-----.
// |  _  |  _  |______|  _  |   _|  _  |_   _|  |  |______|  __|  _  |  __|     |  -__|
// |___  |_____|      |   __|__| |_____|__.__|___  |      |____|___._|____|__|__|_____|
// |_____|            |__|                   |_____|
//
// Copyright (c) 2023 Fabio Cicerchia. https://fabiocicerchia.it. MIT License
// Repo: https://github.com/fabiocicerchia/go-proxy-cache

import (
    "time"

    "github.com/sirupsen/logrus"
    "github.com/sony/gobreaker"
)

var cb map[string]*gobreaker.CircuitBreaker = make(map[string]*gobreaker.CircuitBreaker)

// CircuitBreaker - Settings for redis circuit breaker.
type CircuitBreaker struct {
    FailureRate float64
    Interval    time.Duration
    Timeout     time.Duration
    Threshold   uint32
    MaxRequests uint32
}

// InitCircuitBreaker - Initialise the Circuit Breaker.
func InitCircuitBreaker(name string, config CircuitBreaker, logger *logrus.Logger) {
    st := gobreaker.Settings{
        Name:          name,
        MaxRequests:   config.MaxRequests,
        Interval:      config.Interval,
        Timeout:       config.Timeout,
        ReadyToTrip:   cbReadyToTrip(config),
        OnStateChange: cbOnStateChange(logger),
    }

    cb[name] = gobreaker.NewCircuitBreaker(st)
}

func cbReadyToTrip(config CircuitBreaker) func(counts gobreaker.Counts) bool {
    return func(counts gobreaker.Counts) bool {
        failureRatio := float64(counts.TotalFailures) / float64(counts.Requests)

        return counts.Requests >= config.Threshold && failureRatio >= config.FailureRate
    }
}

func cbOnStateChange(log *logrus.Logger) func(name string, from gobreaker.State, to gobreaker.State) {
    return func(name string, from gobreaker.State, to gobreaker.State) {
        log.Warnf("Circuit Breaker '%s' - Changed from %s to %s", name, from.String(), to.String())
    }
}

// CB - Returns instance of gobreaker.CircuitBreaker.
func CB(name string, log *logrus.Logger) *gobreaker.CircuitBreaker {
    if val, ok := cb[name]; ok {
        return val
    }

    log.Warnf("Missing circuit breaker for %s", name)

    return nil
}