m5app/internal/server/server.go

package server

import (
	"context"
	//"syscall"
	//"os"
	//"os/signal"

	//"errors"
	//"flag"
	//"fmt"
	"os"
	"os/signal"
	"os/user"
	"path/filepath"
	"strconv"
	"syscall"

	"engine/internal/config"
	"engine/internal/handler"
	"engine/internal/logger"
	"engine/internal/logic"
	"engine/internal/service"
)

type Server struct {
	conf *config.Config
	svc  *service.Service
	lg   *logic.Logic
	hand *handler.Handler
	ctx  context.Context
	canc context.CancelFunc
	log  *logger.Logger
}

func NewServer() (*Server, error) {
	var err error
	srv := &Server{
		log: logger.NewLogger("server"),
	}
	srv.ctx, srv.canc = context.WithCancel(context.Background())
	return srv, err
}

func (srv *Server) Configure() error {
	var err error
	srv.log.Infof("Configure server")
	srv.conf = config.NewConfig()
	err = srv.conf.ReadFile()
	if err != nil {
		return err
	}
	err = srv.conf.ReadEnv()
	if err != nil {
		return err
	}
	err = srv.conf.ReadOpts()
	if err != nil {
		return err
	}
	yamlConfig, err := srv.conf.Yaml()
	if err != nil {
		return err
	}
	srv.log.Debugf("Server configuration: \n%s\n", yamlConfig)
	return err
}

func (srv *Server) PseudoFork() error {
	const successExit int = 0
	var keyEnv string = "IMX0LTSELMRF8K"
	var err error

	_, isChild := os.LookupEnv(keyEnv)
	switch {
	case !isChild:
		os.Setenv(keyEnv, "TRUE")

		procAttr := syscall.ProcAttr{}
		cwd, err := os.Getwd()
		if err != nil {
			return err
		}
		var sysFiles = make([]uintptr, 3)
		sysFiles[0] = uintptr(syscall.Stdin)
		sysFiles[1] = uintptr(syscall.Stdout)
		sysFiles[2] = uintptr(syscall.Stderr)

		procAttr.Files = sysFiles
		procAttr.Env = os.Environ()
		procAttr.Dir = cwd

		_, err = syscall.ForkExec(os.Args[0], os.Args, &procAttr)
		if err != nil {
			return err
		}
		os.Exit(successExit)
	case isChild:
		_, err = syscall.Setsid()
		if err != nil {
			return err
		}
	}
	os.Unsetenv(keyEnv)
	return err
}

func (srv *Server) Daemonize() error {
	var err error
	if srv.conf.Daemon {
		srv.log.Debugf("Running server as daemon")
		// Restart process process
		err = srv.PseudoFork()
		if err != nil {
			return err
		}
		currUser, err := user.Current()
		if err != nil {
			return err
		}
		currID, err := strconv.Atoi(currUser.Uid)
		if err != nil {
			return err
		}
		if currID == 0 {
			// Change GID
			sysGroup, err := user.LookupGroup(srv.conf.Group)
			if err != nil {
				return err
			}
			gid, err := strconv.Atoi(sysGroup.Gid)
			if err != nil {
				return err
			}
			err = syscall.Setgid(gid)
			if err != nil {
				return err
			}
			// Change UID
			sysUser, err := user.Lookup(srv.conf.User)
			if err != nil {
				return err
			}
			uid, err := strconv.Atoi(sysUser.Uid)
			if err != nil {
				return err
			}
			err = syscall.Setuid(uid)
			if err != nil {
				return err
			}
		}
		// Redirect stdin
		nullFile, err := os.OpenFile("/dev/null", os.O_RDWR, 0)
		if err != nil {
			return err
		}
		err = syscall.Dup2(int(nullFile.Fd()), int(os.Stdin.Fd()))
		if err != nil {
			return err
		}
		// Redirect stderr and stout
		logdir := filepath.Dir(srv.conf.LogPath)
		err = os.MkdirAll(logdir, 0750)
		if err != nil {
			return err
		}
		logFile, err := os.OpenFile(srv.conf.LogPath, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0640)
		if err != nil {
			return err
		}
		err = syscall.Dup2(int(logFile.Fd()), int(os.Stdout.Fd()))
		if err != nil {
			return err
		}
		err = syscall.Dup2(int(logFile.Fd()), int(os.Stderr.Fd()))
		if err != nil {
			return err
		}
		// Write process ID
		rundir := filepath.Dir(srv.conf.RunPath)
		err = os.MkdirAll(rundir, 0750)
		if err != nil {
			return err
		}
		pidFile, err := os.OpenFile(srv.conf.RunPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0640)
		if err != nil {
			return err
		}
		defer pidFile.Close()
		currPid := os.Getpid()
		_, err = pidFile.WriteString(strconv.Itoa(currPid))
		if err != nil {
			return err
		}
	}
	return err
}

func (srv *Server) Build() error {
	var err error
	srv.log.Infof("Build server")

	// Create logic
	logicConfig := &logic.LogicConfig{}
	srv.lg, err = logic.NewLogic(logicConfig)
	if err != nil {
		return err
	}
	// Create handler
	handlerConfig := &handler.HandlerConfig{
		Logic: srv.lg,
	}
	srv.hand, err = handler.NewHandler(handlerConfig)
	if err != nil {
		return err
	}
	// Create service
	serviceConfig := &service.ServiceConfig{
		PortNum: srv.conf.Service.PortNum,
		WebDir:  srv.conf.Service.WebDir,
		Handler: srv.hand,
	}
	srv.svc, err = service.NewService(serviceConfig)
	if err != nil {
		return err
	}
	err = srv.svc.Build()
	if err != nil {
		return err
	}

	return err
}

func (srv *Server) Run() error {
	var err error
	srv.log.Infof("Running server")

	sigs := make(chan os.Signal, 1)
	done := make(chan error, 1)

	startService := func(svc *service.Service, done chan error) {
		err = svc.Run()
		if err != nil {
			srv.log.Errorf("Service error: %v", err)
			done <- err
		}
	}
	go startService(srv.svc, done)

	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
	var signal os.Signal
	select {
	case signal = <-sigs:
		srv.log.Infof("Services stopped by signal: %v", signal)
		srv.svc.Stop()
	case err = <-done:
		srv.log.Infof("Service stopped by error: %v", err)
		srv.svc.Stop()
	}
	if signal == syscall.SIGHUP {
		//srv.PseudoFork()
	}
	return err
}