What is golang rate? Detailed explanation of rate usage

Go language is an efficient, concurrent and system-level programming language. The Rate package is a very useful package in the Go language that allows you to control the rate of various operations. In this article, we will introduce the usage of Rate package to help you better master its use.

1. Overview of Rate package

Rate package is a package in the Go language standard library. It provides a method to perform certain operations at a fixed rate. For example, we can use this package to limit the API request rate, control the rate at which certain operations are performed, and so on.

This package provides two common rate limiting methods: limiting the rate at which certain operations are performed per second or the rate at which certain operations are performed per unit time. These two restriction methods can be freely set manually using the time.Duration type of the go language to meet their respective needs.

2. Basic usage

1. Basic operations

Rate package provides two operations: Allow() and Limit(). The basic form of the token bucket algorithm is defined in the Allow() method. That is, how many tokens are in the token bucket, then the defined operation can be allowed. Limit() returns two values ​​containing used and available tokens.

2. Perform certain operations at a fixed rate

If we need to perform certain operations at a fixed rate for each operation, the Rate package provides limiter: an instance that limits the execution of operations at a certain rate API interface. For example:

func main() {
    rate := rate.NewLimiter(10, 1)
    for i := 1; i <= 50; i++ {
        if rate.Allow() == false {
            fmt.Println("No allowance for", i)
            continue
        }
        fmt.Println("Hello", i)
    }
}

In the above code, we create an instance rate, which will perform operations with a rate limit of 10 operations per second. Then we loop and perform the operation 50 times. If the operation is not allowed, the current operation is skipped. Otherwise, it executes and prints Hello along with the number of operations.

3. Limit the execution of operations within a period of time

In addition to limiting operations at a fixed rate of operations per second, the Rate package also provides a method: to operate within a given period of time number limit. For example:

func main() {
    limit := rate.NewLimiter(1, 1)
    duration := time.Minute
    operations := 10
    
    timeStart := time.Now()

    for i := 0; i < operations; i++ {
        if err := limit.Wait(ctx); err != nil {
            log.Fatalf("Error waiting on limiter: %v", err)
        }
        // Execute operation
    }

    timeEnd := time.Now()

    elapsedTime := timeEnd.Sub(timeStart)

    fmt.Printf("Executed %v operations in %v", operations, elapsedTime)
}

In this code, we create an operation limit instance and limit the number of operations to 1 per minute. The operation instance waits for a signal that the operation can be performed, and then performs the operation. We can also set the limit time to other values ​​using the WithTimeout function of the ctx parameter.

4. Perform operations in burst mode

When we need to perform operations in burst mode, we can use a Bucket instance to do it. Bucket instances are similar to Limiter instances, but they have a higher burst control threshold.

For example:

func main() {
        b := rate.NewBucket(time.Second*1, 50)
        t := time.Now()
        for i := 0; i < 110; i++ {
                t = b.Take(1)
                fmt.Printf("i: %v t: %v\n", i, t.UnixNano())
        }
}

In the above code, we create a Bucket instance that performs operations with a rate limit of 50 operations every 1 second. Then we loop the operation 110 times. Since the burst control threshold is 50, the first 50 operations will be able to be executed immediately. But wait for the running time of subsequent operations to keep the burst window no longer than 50 operations.

Summary

We have mastered the basic use of the Rate package and used the above examples to demonstrate how to perform operations at a fixed rate, per time period, and in burst mode. In addition, the package provides some other useful methods (such as SetLimit() and LimitAt()) that can help you better control the rate of operations. Cherish life and stay away from the risk of frequent account bans.

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