How to use context to implement request concurrency control in Go

As a high-performance programming language, Go language has always been outstanding in its concurrent programming capabilities. In order to better manage and control concurrent requests, in Go language, we can use context to implement request concurrency control. This article will introduce how to use context to implement request concurrency control in Go language, and demonstrate it through code examples.

Introduction to Context

In the Go language, the context package provides a way to manage collision requests. It can pass request-wide data between goroutines, including deadlines, timeouts, cancellation signals, etc. By using context, we can better manage and control concurrent requests.

Steps to use context to implement request concurrency control

The following are the steps to use context to implement request concurrency control:

1. Create root context: First, we need to create a root context. The root context is the parent context of all child contexts. We can use context.TODO() or context.Background() to create an empty root context.

ctx := context.TODO()

2. Create subcontext: Next, we can use the context.WithXXX() function to create a subcontext. This function receives a parent context as a parameter and returns a new child context.

childCtx := context.WithTimeout(ctx, time.Second*10)

In the above code, we use the context.WithTimeout() function to create a subcontext with a timeout of 10 seconds.

3. Processing requests: When processing specific requests, we can use context.Context type parameters to receive the passed context. During the process of processing the request, we can use the context.Context method to obtain context-related information.

func HandleRequest(ctx context.Context) {
    // 处理请求
}

4. Control concurrency: When making concurrent requests, we can use the Done() method of context.Context to determine whether the request has been canceled or timed out. When the Done() method is called, it returns a read-only Channel. If the request is canceled or times out, the Done() method will close the Channel.

go func() {
    for {
        select {
        case <-ctx.Done():
            return
        default:
            // 发起请求
            HandleRequest(ctx)
        }
    }
}()

In the above code, we use a for loop and select statement to monitor the Done() method of context. When the Done() method returns, we know that the request has been canceled or timed out and we can exit the loop.

5. Cancel Request: In some cases we wish to cancel a request that is being processed. At this time, we can call the cancel() method of type context.CancelFunc to cancel the request.

cancel()

In the above code, we call the cancel() method to cancel the request.

Sample code

The following is a simple sample code that demonstrates how to use context to implement request concurrency control.

package main

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

func Worker(ctx context.Context, wg *sync.WaitGroup) {
    defer wg.Done()
 
    for {
        select {
        case <-ctx.Done():
            // 请求已被取消或超时
            return
        default:
            // 处理请求
            fmt.Println("Handling request...")
            time.Sleep(time.Second * 1)
        }
    }
}

func main() {
    ctx := context.TODO()
    childCtx, cancel := context.WithTimeout(ctx, time.Second*5)
    defer cancel()

    var wg sync.WaitGroup
    for i := 0; i < 5; i++ {
        wg.Add(1)
        go Worker(childCtx, &wg)
    }

    wg.Wait()
    fmt.Println("All requests processed")
}

In the above code, we create a root context and a child context with a timeout of 5 seconds. Then, we created 5 goroutines to handle the requests. During the process of processing the request, we use the context's Done() method to determine whether the request was canceled or timed out. Finally, we use sync.WaitGroup to wait for all requests to be processed.

Summary

By using context, we can better manage and control concurrent requests. This article introduces the steps to use context to implement request concurrency control and demonstrates it through sample code. I believe that readers can better understand and apply context to achieve request concurrency control through the introduction and sample code of this article.

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