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package main
import (
"fmt"
"log"
"net/http"
"time"
_ "net/http/pprof"
"github.com/felixge/fgprof"
)
const (
sleepTime = 10 * time.Millisecond
cpuTime = 30 * time.Millisecond
networkTime = 60 * time.Millisecond
)
// sleepURL is the url for the sleep server used by slowNetworkRequest. It's
// a global variable to keep the cute simplicitly of main's loop.
var sleepURL string
func main() {
// Run http endpoints for both pprof and fgprof.
http.DefaultServeMux.Handle("/debug/fgprof", fgprof.Handler())
go func() {
addr := "localhost:6060"
log.Printf("Listening on %s", addr)
log.Println(http.ListenAndServe(addr, nil))
}()
// Start a sleep server to help with simulating slow network requests.
var stop func()
sleepURL, stop = StartSleepServer()
defer stop()
for {
// Http request to a web service that might be slow.
slowNetworkRequest()
// Some heavy CPU computation.
cpuIntensiveTask()
// Poorly named function that you don't understand yet.
weirdFunction()
}
}
func slowNetworkRequest() {
res, err := http.Get(sleepURL + "/?sleep=" + networkTime.String())
if err != nil {
panic(err)
}
defer res.Body.Close()
if res.StatusCode != 200 {
panic(fmt.Sprintf("bad code: %d", res.StatusCode))
}
}
func cpuIntensiveTask() {
start := time.Now()
for time.Since(start) <= cpuTime {
// Spend some time in a hot loop to be a little more realistic than
// spending all time in time.Since().
for i := 0; i < 1000; i++ {
_ = i
}
}
}
func weirdFunction() {
time.Sleep(sleepTime)
}
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