concord/internal/circuitbreaker/breaker.go

package circuitbreaker

import (
	"errors"
	"sync"
	"time"
)

var ErrCircuitOpen = errors.New("circuit breaker is open")

type State int

const (
	StateClosed State = iota
	StateOpen
	StateHalfOpen
)

type CircuitBreaker struct {
	maxFailures int
	timeout     time.Duration
	state       State
	failures    int
	lastFailure time.Time
	mu          sync.RWMutex
}

func New(maxFailures int, timeout time.Duration) *CircuitBreaker {
	return &CircuitBreaker{
		maxFailures: maxFailures,
		timeout:     timeout,
		state:       StateClosed,
	}
}

func (cb *CircuitBreaker) Call(fn func() error) error {
	cb.mu.Lock()
	defer cb.mu.Unlock()

	if cb.state == StateOpen {
		if time.Since(cb.lastFailure) > cb.timeout {
			cb.state = StateHalfOpen
		} else {
			return ErrCircuitOpen
		}
	}

	err := fn()
	if err != nil {
		cb.failures++
		cb.lastFailure = time.Now()

		if cb.failures >= cb.maxFailures {
			cb.state = StateOpen
		}

		return err
	}

	if cb.state == StateHalfOpen {
		cb.state = StateClosed
	}

	cb.failures = 0
	return nil
}

func (cb *CircuitBreaker) GetState() State {
	cb.mu.RLock()
	defer cb.mu.RUnlock()
	return cb.state
}

func (cb *CircuitBreaker) Reset() {
	cb.mu.Lock()
	defer cb.mu.Unlock()
	cb.state = StateClosed
	cb.failures = 0
}