[08] Go Design Patterns: Proxy mode (ProxyPattern)

proxy

I. Introduction

Proxy design pattern is a design pattern. This mode is recommended to provide an additional layer of indirection to control and access the main target.

In this mode, creates a new proxy class that implements the same interface to the main subject. This allows you to perform certain actions before the actual logic of the main subject or later.

Second, the code

package main

import "fmt"

type server interface {
    handleRequest(string, string) (int, string)
}

type nginx struct {
    application       *application
    maxAllowedRequest int
    rateLimiter       map[string]int
}

func newNginxServer() *nginx {
    return &nginx{
        application:       &application{},
        maxAllowedRequest: 2,
        rateLimiter:       make(map[string]int),
    }
}

func (n *nginx) handleRequest(url, method string) (int, string) {
    allowed := n.checkRateLimiting(url)
    if !allowed {
        return 403, "Not Allowed"
    }
    return n.application.handleRequest(url, method)
}

func (n *nginx) checkRateLimiting(url string) bool {
    if n.rateLimiter[url] == 0 {
        n.rateLimiter[url] = 1
    }
    if n.rateLimiter[url] > n.maxAllowedRequest {
        return false
    }
    n.rateLimiter[url] = n.rateLimiter[url] + 1
    return true
}

type application struct {
}

func (a *application) handleRequest(url, method string) (int, string) {
    if url == "/app/status" && method == "GET" {
        return 200, "Ok"
    }
    if url == "/create/user" && method == "POST" {
        return 201, "User Created"
    }
    return 404, "Not Ok"
}

func main() {
    nginxServer := newNginxServer()
    appStatusURL := "/app/status"
    createuserURL := "/create/user"
    httpCode, body := nginxServer.handleRequest(appStatusURL, "GET")
    fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body)
    httpCode, body = nginxServer.handleRequest(appStatusURL, "GET")
    fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body)
    httpCode, body = nginxServer.handleRequest(appStatusURL, "GET")
    fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body)
    httpCode, body = nginxServer.handleRequest(createuserURL, "POST")
    fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body)
    httpCode, body = nginxServer.handleRequest(createuserURL, "GET")
    fmt.Printf("\nUrl: %s\nHttpCode: %d\nBody: %s\n", appStatusURL, httpCode, body)
}

Third, reference materials

1、https://golangbyexample.com/proxy-design-pattern-in-golang/