serve.go

package main

import (
	"fmt"
	"net/http"
	"sync"
	"time"
)

type Task struct {
	IP      string
	IsDone  bool
	Done    chan struct{}
	Request *http.Request
}

type Queue struct {
	LastTask *Task
	Mutex    sync.Mutex
}

var queues sync.Map

func longRunningTask(task *Task) {
	// Simulate a long running task
	time.Sleep(5 * time.Second)

	// Mark the task as done
	task.IsDone = true
	close(task.Done)
	queues.Delete(task.IP)
}

func requestHandler(w http.ResponseWriter, r *http.Request) {
	ip := r.RemoteAddr

	value, _ := queues.LoadOrStore(ip, &Queue{})
	queue := value.(*Queue)

	queue.Mutex.Lock()
	defer queue.Mutex.Unlock()

	// If there's an ongoing task for the IP, replace the request in the queue with the current request
	if queue.LastTask != nil && !queue.LastTask.IsDone {
		queue.LastTask.Request = r
		http.Error(w, "Request queued, waiting for ongoing task to finish", http.StatusAccepted)
		return
	}

	// Start a new long-running task with the current request
	task := &Task{
		IP:      ip,
		IsDone:  false,
		Done:    make(chan struct{}),
		Request: r,
	}
	queue.LastTask = task

	go longRunningTask(task)

	// Send a response to the client
	fmt.Fprintf(w, "New task started for IP: %s\n", ip)
}

func main() {
	http.HandleFunc("/", requestHandler)
	http.ListenAndServe(":8080", nil)
}