TorfluxProxy: Anonymous metrics from Go - Demo 5

demo.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"math/rand"
	"time"

	"github.com/rcrowley/go-metrics"
)

var (
	clientCounter = metrics.NewCounter()
	egressMeter   = metrics.NewMeter()
)

func main() {
	// Start a goroutine to report the stats to the user
	go func() {
		for {
			fmt.Printf("Connected clients: %2d, egress bandwidth: %2.2f MB/s\n",
				clientCounter.Count(), egressMeter.Rate1()/1024/1024)
			time.Sleep(5 * time.Second)
		}
	}()
	// Simulate a new client connecting every half a second, requesting data. To
	// avoid going out of memory, lets also set a max connection limit of 10.
	slots := make(chan struct{}, 10)

	for {
		// Fetch the next connection slot to avoid overloading
		slots <- struct{}{}

		// Simulate a random client retrieving some file from the server
		go func() {
			serve(ioutil.Discard)
			<-slots // return the slot
		}()
		time.Sleep(500 * time.Millisecond)
	}
}

// serve is a simple file server simulator that writes random-length blobs to the
// provided streams bfore returning.
func serve(conn io.Writer) {
	// Track this client while it's connected
	clientCounter.Inc(1)
	defer clientCounter.Dec(1)

	// Stream a randomly sized file in 512KB chunks to the connection
	file := make([]byte, rand.Intn(16*1024*1024))

	// Simulate the peer having a certain bandwidth, delaying each chunk a bit
	delay := time.Duration(rand.Intn(500)) * time.Millisecond

	for len(file) > 512*1024 {
		egressMeter.Mark(512 * 1024)
		conn.Write(file[:512*1024])

		file = file[512*1024:]
		time.Sleep(delay)
	}
	egressMeter.Mark(int64(len(file)))
	conn.Write(file) // Yeah, no more sleep, insta-send!
}