feat(experiment/bg): added bg utility to help pid proxy testing

feat(experiment/starter): added option to skip waiting for child process

cmd/experiment/bg/Makefile

@@ -0,0 +1,10 @@
+all:
+	git describe > version.txt
+	go build -v
+
+clean:
+	echo "dev" > version.txt
+	go clean -i -cache -testcache
+
+install:
+	install bg ${DESTDIR}/wmbg

cmd/experiment/bg/background.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"github.com/spf13/pflag"
+	"golang.org/x/sys/unix"
+)
+
+const (
+	logPathFlag = "log-path"
+	pidFileFlag = "pid-file"
+)
+
+func main() {
+	var (
+		logPath     string
+		pidFilePath string
+		name        string
+		pause       uint
+		lf          *os.File
+		err         error
+	)
+
+	pflag.StringVarP(&logPath, logPathFlag, "l", "/var/log/wmbg.log", "log file path")
+	pflag.StringVarP(&pidFilePath, pidFileFlag, "p", "/var/run/wmbg.pid", "pid file path")
+	pflag.StringVar(&name, "name", "no-name", "process name")
+	pflag.UintVar(&pause, "pause", 5, "pause interval")
+	pflag.Parse()
+
+	if lf, err = os.OpenFile(logPath, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644); err != nil {
+		os.Exit(2)
+	}
+	defer func() {
+		_ = lf.Close()
+	}()
+
+	log.SetOutput(lf)
+	log.Printf("starting process %s with pause interval %d", name, pause)
+	if err = writePid(pidFilePath); err != nil {
+		log.Printf("failed to write pid file: %+v", err)
+	}
+	time.Sleep(time.Duration(pause) * time.Second)
+	log.Printf("process %s finished", name)
+}
+
+func writePid(path string) error {
+	var (
+		err error
+		pf  *os.File
+	)
+
+	if pf, err = os.OpenFile(path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644); err != nil {
+		return fmt.Errorf("opening pid file for write: %w", err)
+	}
+	defer func() {
+		_ = pf.Close()
+	}()
+
+	if _, err = fmt.Fprintf(pf, "%d", unix.Getpid()); err != nil {
+		return fmt.Errorf("writing pid to the pid file: %w", err)
+	}
+	return nil
+}

cmd/experiment/bg/version.txt

@@ -0,0 +1 @@
+dev