golang concurrent requests

In today's Internet era, requesting and processing data quickly and efficiently is an essential skill for all program developers. Concurrent requests are one of the effective ways to achieve this goal. This article will introduce how to implement concurrent requests in golang.

1. What is concurrent request

Concurrent request refers to sending requests to multiple servers at the same time to speed up data request and processing and reduce response time. This is very useful in tasks where there is a large amount of data to be processed, such as crawling, processing big data, etc.

2. How to implement concurrent requests in golang

Concurrent requests are implemented in golang through coroutines and pipelines. Coroutines are lightweight threads in golang. They can run multiple coroutines in one thread at the same time to achieve concurrency. Pipes are a way of communication between coroutines, used to transfer data and control the execution flow.

1. Using goroutine

In golang, we can use goroutine to handle concurrent requests. Let's look at a simple example:

package main

import (
    "fmt"
    "net/http"
)

func main() {
    websites := []string{
        "https://www.baidu.com",
        "https://www.google.com",
        "https://www.bing.com",
    }

    for _, url := range websites {
        go func(u string) {
            resp, err := http.Get(u)
            if err != nil {
                fmt.Println(u, "is not available")
            } else {
                fmt.Println(u, "status is", resp.Status)
            }
        }(url)
    }
}

In this code, we define a slice containing three website addresses, then use a for loop to traverse the slice, and use the go keyword in the loop body to start a protocol Processes, each coroutine is responsible for requesting the content of a website. If there is an error in the request, we will output an error message; if the request is successful, we will output a status code.

In this example, because we use goroutine, the three requests are performed at the same time and will not block each other. This greatly improves the execution efficiency of the program.

2. Use channel

In golang, we can use channel to solve the communication problem between goroutines. In concurrent requests, we can use channels to pass data and control the execution flow.

Let’s look at a specific example:

package main

import (
    "fmt"
    "net/http"
)

func main() {
    websites := []string{
        "https://www.baidu.com",
        "https://www.google.com",
        "https://www.bing.com",
    }

    ch := make(chan string)

    for _, url := range websites {
        go func(u string) {
            resp, err := http.Get(u)
            if err != nil {
                ch <- fmt.Sprintf("%s is not available", u)
            } else {
                ch <- fmt.Sprintf("%s status is %s", u, resp.Status)
            }
        }(url)
    }

    for i := 0; i < len(websites); i++ {
        fmt.Println(<-ch)
    }
}

In this example, we define a channel to deliver the results of each website request. In goroutine, if the request is successful, the result is sent to the channel; if the request fails, an error message is sent. Then, use a for loop in the main coroutine to wait for all results to return. Here, the blocking read operation of the channel is used

By using channels, we can ensure that the results of each request are output in the order they are sent, without blocking the execution of other requests.

3. Summary

It is very simple to implement concurrent requests in golang. You only need to use goroutine and channel. Using these two functions, we can send multiple requests at the same time, improving the performance and efficiency of the program.

But concurrent requests also have some problems, such as putting excessive pressure on the server. When using concurrent requests, we need to exercise reasonable control based on the specific situation to avoid burdening the server.

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