分布式系统中限流和熔断机制至关重要,go 框架提供了广泛的实现机制。限流旨在防止过载,例如限制每秒 http 请求数量。熔断则在服务失败或响应时间过长时,暂时阻止对服务的访问,以避免级联故障。
Go 框架限流和熔断在分布式系统中的应用
在现代分布式系统中,限流和熔断机制对于确保系统稳定性和弹性至关重要。Go 语言提供了广泛的框架来简化这些机制的实现。
限流
立即学习“go语言免费学习笔记(深入)”;
限流机制旨在防止系统因过载而崩溃。
import (
"context"
"github.com/golang/groupcache/lru"
"time"
)
// LimitRequests 限制每秒请求
func LimitRequests(ctx context.Context, maxRequests, d time.Duration) (func(), error) {
l := lru.New(maxRequests)
go func() {
for {
time.Sleep(d)
l.Purge()
}
}()
return func() bool {
return l.Add(0, nil) != nil
}, nil
}
实战示例:
使用限流来限制每秒处理的 HTTP 请求数量:
import (
"github.com/buaazp/fasthttprouter"
"time"
)
func main() {
limiter, err := LimitRequests(context.Background(), 10, time.Second)
if err != nil {
log.Fatal(err)
}
router := fasthttprouter.New()
router.GET("/", func(ctx *fasthttp.RequestCtx) {
if limiter() {
ctx.Error("Too many requests", fasthttp.StatusTooManyRequests)
return
}
// 处理请求...
})
server.ListenAndServe(":8080")
}
熔断
熔断机制旨在在服务失败或响应时间过长时暂时阻止对服务的访问。
import (
"context"
"errors"
"sync"
"time"
)
// CircuitBreaker 熔断器
type CircuitBreaker struct {
sync.Mutex
state State
closedAt time.Time
failedReq int
successReq int
}
// State 熔断状态
type State int
const (
Closed State = iota
HalfOpen
Open
)
// Trip 熔断
func (cb *CircuitBreaker) Trip() {
cb.Lock()
defer cb.Unlock()
cb.failedReq++
cb.state = Open
cb.closedAt = time.Now().Add(time.Minute)
}
// Close 关闭熔断
func (cb *CircuitBreaker) Close() {
cb.Lock()
defer cb.Unlock()
cb.state = Closed
cb.closedAt = time.Now()
}
// Allow 通过请求
func (cb *CircuitBreaker) Allow() error {
cb.Lock()
defer cb.Unlock()
now := time.Now()
if cb.state == Open && cb.closedAt.After(now) {
return errors.New("circuit open")
}
if cb.state == HalfOpen {
cb.state = Closed
cb.successReq++
}
return nil
}
实战示例:
使用熔断器来保护对外部服务的调用:
import (
"errors"
"time"
"github.com/sony/gobreaker"
"github.com/uber/jaeger-client-go"
)
var (
jaegerCloser jaeger.Closer
cb = gobreaker.NewCircuitBreaker(gobreaker.Settings{
// 连续请求失败才会熔断
Interval: 10 * time.Second,
})
fallbackCallCount int
)
func MakeRemoteCall() (string, error) {
err := cb.Execute(func() (string, error) {
return "some result", nil
})
if err != nil {
fallbackCallCount++
return "fallback result", nil
}
return "result", nil
}