How to implement request forwarding function in golang

With the development of the Internet, more and more services are deployed on the cloud, especially the microservice architecture is becoming increasingly popular. In this context, communication between services has become increasingly important. In some scenarios, we need to expose a service to the public network and at the same time hope that it can forward requests to other services. In this case, we need to use golang to forward requests.

Golang is an efficient programming language with good concurrency performance and compilation speed, and is also very suitable for building back-end applications. Therefore, in scenarios where forwarding requests are required, we can choose to use golang for development.

Next, we will introduce how golang implements the request forwarding function from the following aspects:

1. Using the http package for request forwarding

golang's The standard library contains the http package, which can be used to easily forward requests. The following is a simple example code:

package main

import (
  "fmt"
  "net/http"
  "net/http/httputil"
)

func main() {
  targetURL := "http://example.com"

  director := func(req *http.Request) {
    req.URL.Scheme = "http"
    req.URL.Host = targetURL
  }

  proxy := &httputil.ReverseProxy{Director: director}

  http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    proxy.ServeHTTP(w, r)
  })

  http.ListenAndServe(":8080", nil)
}

The above code will forward all requests received to the target address "example.com" and return the response of the target address to the client.

In the above code, we use the ReverseProxy structure to proxy the request. Among them, the Director function specifies the target URL, and the ReverseProxy structure is responsible for forwarding the request to the target address.

2. Request forwarding of multiple target addresses

Sometimes we may need to distribute the same request to multiple different services to improve system availability and stability sex. The following is a sample code that supports multiple destination addresses:

package main

import (
  "fmt"
  "net/http"
  "net/http/httputil"
  "strings"
)

func main() {
  targetURLs := []string{"http://example1.com", "http://example2.com"}

  director := func(req *http.Request) {
    targetURL := targetURLs[0]
    if len(targetURLs) > 1 {
      targetURL = targetURLs[0]
      targetURLs = append(targetURLs[1:], targetURL)
    }

    req.URL.Scheme = "http"
    req.URL.Host = targetURL
  }

  proxy := &httputil.ReverseProxy{Director: director}

  http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    proxy.ServeHTTP(w, r)
  })

  http.ListenAndServe(":8080", nil)
}

The above code forwards the request to the two addresses example1.com and example2.com, and Each request will select a target address in order for forwarding. In this way, when one of the services is unavailable, the request will automatically switch to another available target address.

3. Filter implements request forwarding

In actual scenarios, we may need to perform some specific processing on certain requests, such as verifying user identity, limiting access frequency, etc. . At this point, filters can be used to forward requests. The following is a sample code for using filters:

package main

import (
  "fmt"
  "net/http"
  "net/http/httputil"
  "strings"
)

func main() {
  targetURL := "http://example.com"

  director := func(req *http.Request) {
    req.URL.Scheme = "http"
    req.URL.Host = targetURL
  }

  filter := func(h http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
      // 进行请求过滤操作，例如验证用户身份、限制访问频率等

      h.ServeHTTP(w, r)
    })
  }

  proxy := &httputil.ReverseProxy{Director: director}
  handler := filter(proxy)

  http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    handler.ServeHTTP(w, r)
  })

  http.ListenAndServe(":8080", nil)
}

The above code adds a filter function to the original one. This function is used to implement the request filtering operation and pass the filtered request to the original processing function. In this way, we can further process and filter the request before forwarding it.

Summary

In this article, we introduced the basic content of golang forwarding requests. Using golang to implement the request forwarding function can not only improve the availability and stability of the system, but also improve the performance of the system. Of course, in practical applications, there are many factors we need to consider, such as load balancing of the target service, request logging, etc. Hope this article is helpful to everyone.

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