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generator.go
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/
generator.go
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package fakelog
import (
"fmt"
"io"
"math/rand"
"strconv"
"strings"
"time"
)
const (
maxRate = 1000
apacheTimeFormat = "02/01/2006:15:04:05 -0700" // dd/MMM/yyyy:hh:mm:ss +-hhmm
)
// LineGenerator is the signature of fake log lines generating function.
type LineGenerator func() string
// Logger generates fake and random log lines.
type Logger struct {
lineFn LineGenerator
out io.WriteCloser
rate int
cancel chan bool
}
// NewLogger returns configured Logger, enforcing sensible rate.
func NewLogger(lineFn LineGenerator, out io.WriteCloser, rate int) *Logger {
if rate > maxRate || rate == 0 {
rate = maxRate
}
return &Logger{
lineFn: lineFn,
out: out,
rate: rate,
cancel: make(chan bool),
}
}
// GenerateLogs generates W3-c common log lines with rps of rate to the output out.
func (g *Logger) GenerateLogs() error {
// we want a bit randomized rate, therefore avoiding to use a predictive ticker
sleepBase := int64((1.0 / float64(g.rate)) * float64(maxRate))
for {
select {
case <-g.cancel:
return nil
default:
line := g.lineFn()
if _, err := g.out.Write([]byte(line + "\n")); err != nil {
return fmt.Errorf("unable to write log line to out: %v", err)
}
// if we want to get close to maxRate wa can't sleep at all
if sleepBase != 0 {
add := rand.Int63n((sleepBase / 5) + 1)
var d time.Duration
if add%2 == 0 {
d = time.Duration(sleepBase - add)
} else {
d = time.Duration(sleepBase + add)
}
time.Sleep(d * time.Millisecond)
}
}
}
}
// Stop notifies the cancel chanel of a Logger, resulting into stopping it's log generation in GenerateLogs().
func (g *Logger) Stop() {
g.cancel <- true
}
// ApacheCommonLine generates an apache common access log line. It implements the Line generator func signature.
// format source: https://httpd.apache.org/docs/2.4/logs.html#accesslog
func ApacheCommonLine() string {
ip := ipV4Address()
u := randomEle(userNames)
dt := time.Now().Format(apacheTimeFormat)
code := codes.next()
size := rand.Intn(30000)
method := methods.next()
ep := endpoints[rand.Intn(len(endpoints)-1)]
if strings.HasSuffix(ep, "/") || strings.HasSuffix(ep, "=") {
ep = ep + strconv.Itoa(rand.Intn(10000))
}
return fmt.Sprintf(`%s %s - [%s] "%s %s HTTP/1.1" %s %d`, ip, u, dt, method, ep, code, size)
}
// ApacheCombinedLine generates an apache combined access log line. It implements the Line generator func signature.
// format source: https://httpd.apache.org/docs/2.4/logs.html#accesslog
func ApacheCombinedLine() string {
ua := randomEle(userAgents)
ref := randomEle(referrers)
return ApacheCommonLine() + fmt.Sprintf(` "%s" "%s"`, ref, ua)
}
func randomEle(in []string) string {
return in[rand.Intn(len(userNames)-1)]
}
func ipV4Address() string {
blocks := []string{}
for i := 0; i < 4; i++ {
number := rand.Intn(255)
blocks = append(blocks, strconv.Itoa(number))
}
return strings.Join(blocks, ".")
}