Multirun start
task id 0 , timeout
task id 1 , timeout
task id 2 , sleep 1 second
Multissh finished. Process time 5s. Number of task is 3
如果修改并发限制为2：
chLimit := make(chan bool, 2)
运行结果：
Multirun start
task id 0 , timeout
task id 1 , timeout
task id 2 , sleep 1 second
Multissh finished. Process time 3s. Number of task is 3
使用计数器实现请求限流
限流的要求是在指定的时间间隔内，server 最多只能服务指定数量的请求。实现的原理是我们启动一个计数器，每次服务请求会把计数器加一，同时到达指定的时间间隔后会把计数器清零；这个计数器的实现代码如下所示：
type RequestLimitService struct {
Interval time.Duration
MaxCount int
Lock sync.Mutex
ReqCount int
}
func NewRequestLimitService(interval time.Duration, maxCnt int) *RequestLimitService {
reqLimit := &RequestLimitService{
Interval: interval,
MaxCount: maxCnt,
}
go func() {
ticker := time.NewTicker(interval)
for {
<-ticker.C
reqLimit.Lock.Lock()
fmt.Println("Reset Count...")
reqLimit.ReqCount = 0
reqLimit.Lock.Unlock()
}
}()
return reqLimit
}
func (reqLimit *RequestLimitService) Increase() {
reqLimit.Lock.Lock()
defer reqLimit.Lock.Unlock()
reqLimit.ReqCount += 1
}
func (reqLimit *RequestLimitService) IsAvailable() bool {
reqLimit.Lock.Lock()
defer reqLimit.Lock.Unlock()
return reqLimit.ReqCount < reqLimit.MaxCount
}
在服务请求的时候, 我们会对当前计数器和阈值进行比较，只有未超过阈值时才进行服务：
var RequestLimit = NewRequestLimitService(10 * time.Second, 5)
func helloHandler(w http.ResponseWriter, r *http.Request) {
if RequestLimit.IsAvailable() {
RequestLimit.Increase()
fmt.Println(RequestLimit.ReqCount)
io.WriteString(w, "Hello world!n")
} else {
fmt.Println("Reach request limiting!")
io.WriteString(w, "Reach request limit!n")
}
}
func main() {
fmt.Println("Server Started!")
http.HandleFunc("/", helloHandler)
http.ListenAndServe(":8000", nil)
}
完整代码 url
使用golang官方包实现httpserver频率限制
使用golang来编写httpserver时，可以使用官方已经有实现好的包：
import(
"fmt"
"net"
"golang.org/x/net/netutil"
)
func main() {
l, err := net.Listen("tcp", "127.0.0.1:0")
if err != nil {
fmt.Fatalf("Listen: %v", err)
}
defer l.Close()
l = LimitListener(l, max)
http.Serve(l, http.HandlerFunc())
//bla bla bla.................
}
