How to implement current limiting in golang

Current limiting is a common strategy to prevent system overload. By limiting the system's request rate, the availability of the system can be guaranteed and data loss caused by system crashes can be prevented. In actual engineering applications, current limiting is often needed to ensure system stability. This article will introduce how to use golang to implement the current limiting function.

1. Current limiting algorithm

The current limiting algorithm refers to an algorithm that controls traffic in some way. Using a current-limiting algorithm in a program generally means controlling the processing speed of the program. Common current limiting algorithms include leaky bucket algorithm and token bucket algorithm.

Leaky bucket algorithm: The leaky bucket algorithm is a leaky bucket with a fixed capacity. Water is added into it at a certain rate. When the water exceeds the capacity of the bucket, it will overflow. That is, if the water flows in faster than the water flows out, the bucket will fill up and subsequent water will be discarded.

Token Bucket Algorithm: The token bucket algorithm is a fixed-capacity token bucket. Tokens are added to it at a certain rate. Each request requires one token to be processed. That is, if there are insufficient tokens, the request will be discarded.

2. Implementing current limiting in golang

To implement the current limiting function in golang, the current limiting algorithm needs to be applied to concurrent programs. Golang provides a built-in sync package that can be used to implement the current limiting function.

The code is implemented as follows:

package main

import (
    "fmt"
    "sync"
    "time"
)

type Limiter struct {
    sync.Mutex
    limit  int
    count  int
    expire time.Time
}

func NewLimiter(limit int, expire time.Duration) *Limiter {
    return &Limiter{
        limit:  limit,
        count:  0,
        expire: time.Now().Add(expire),
    }
}

func (limit *Limiter) Allow() bool {
    limit.Lock()
    defer limit.Unlock()

    if limit.count < limit.limit {
        limit.count++
        return true
    }

    if time.Now().After(limit.expire) {
        limit.count = 1
        limit.expire = time.Now().Add(time.Second)
        return true
    }

    return false
}

func main() {
    limit := NewLimiter(10, time.Second)
    for i := 0; i < 30; i++ {
        if limit.Allow() {
            fmt.Println(i, "allow")
        } else {
            fmt.Println(i, "deny")
        }
        time.Sleep(100 * time.Millisecond)
    }
}

In the above code, we define a Limiter structure, which contains three fields: limit, count, and expire. Limit represents the number of requests allowed per second, count represents the number of requests currently processed, and expire represents the expiration time.

Create a Limiter object through the NewLimiter function, and pass in the request quantity limit and expiration time expire. The Allow method is used to check whether the request is currently allowed to be processed based on the current time and limit and expire restrictions, and update the count and expire fields.

In the main function, we use a loop to test whether Limiter can limit the number of requests processed per second, and use the time.Sleep function to pause for 100 milliseconds.

3. Summary

The current limiting function is a very common requirement in program development. By limiting the rate of requests, you can protect the security and stability of your program. This article introduces how to implement the current limiting function in golang. By using the sync package and Limiter object, we can easily implement flow control for high-concurrency programs.

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