download files to test cache performance

client_downloader.go

package main

import (
	"fmt"
	"io/ioutil"
	"math/rand"
	"net/http"
	"strconv"
	"time"

	"github.com/montanaflynn/stats"
)

const iterations = 10000

func main() {
	var timings stats.Float64Data

	for i := 0; i < iterations; i++ {
		// most frequent items
		fileNum := rand.Intn(10)
		elapsed := fetchAndTime(fileNum)
		timings = append(timings, elapsed)

		// less frequent items
		fileNum = rand.Intn(100)
		elapsed = fetchAndTime(fileNum)
		timings = append(timings, elapsed)

		// finally pollute the cache. fetch a random file not likely to be needed again
		fileNum = rand.Intn(1000)
		for j := 0; j < 10; j++ {
			elapsed := fetchAndTime(fileNum)
			timings = append(timings, elapsed)
		}
	}

	mean, err := stats.Mean(timings)
	if err != nil {
		fmt.Println("Problem with mean", err)
	}
	fmt.Println("The mean response time is:", mean)

	std, err := stats.StandardDeviation(timings)
	if err != nil {
		fmt.Println("Problem with standard deviation", err)
	}
	fmt.Println("The standard deviation is:", std)

	p95, err := stats.Percentile(timings, 95)
	if err != nil {
		fmt.Println("Problem with p95", err)
	}
	fmt.Println("The p95 is:", p95)

	p99, err := stats.Percentile(timings, 99)
	if err != nil {
		fmt.Println("Problem with p99", err)
	}
	fmt.Println("The p99 is:", p99)
}

func fetchAndTime(fileNum int) float64 {
	fileStr := strconv.Itoa(fileNum)
	if fileNum < 10 {
		fileStr = "00" + strconv.Itoa(fileNum)
	} else if fileNum < 100 {
		fileStr = "0" + strconv.Itoa(fileNum)
	}
	start := time.Now()
	resp, err := http.Get("http://127.0.0.1:8080/file" + fileStr + ".bin")
	if err != nil {
		fmt.Println("Problem downloading file number", fileStr)
	}
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		fmt.Println("Error reading body", err)
	} else {
		fmt.Printf("Downloaded file %s of size %d\n", "file"+fileStr+".bin", len(body))
	}
	resp.Body.Close()
	now := time.Now()
	return float64(now.Sub(start).Milliseconds())
}