gohttpserver/httpserver/main.go

package httpserver

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/rs/zerolog"
	"github.com/rs/zerolog/log"
	"github.com/spf13/viper"

	"github.com/getsentry/sentry-go"
	"github.com/go-chi/chi"

	// spooky action at a distance!
	// this populates the environment
	// from a ./.env file automatically
	// for development configuration.
	// .env contents should be things like
	// `DBURL=postgres://user:pass@.../`
	// (without the backticks, of course)
	_ "github.com/joho/godotenv/autoload"
)

type server struct {
	appname       string
	version       string
	buildarch     string
	databaseURL   string
	startupTime   time.Time
	port          int
	exitCode      int
	sentryEnabled bool
	log           *zerolog.Logger
	ctx           context.Context
	cancelFunc    context.CancelFunc
	httpServer    *http.Server
	router        *chi.Mux
}

func NewServer(options ...func(s *server)) *server {
	n := new(server)
	n.startupTime = time.Now()
	n.version = "unknown"
	for _, opt := range options {
		opt(n)
	}

	return n
}

// this is where we come in from package main.
func Run(appname, version, buildarch string) int {
	s := NewServer(func(i *server) {
		i.appname = appname
		if version != "" {
			i.version = version
		}
		i.buildarch = buildarch
	})

	// this does nothing if SENTRY_DSN is unset in env.
	s.enableSentry()

	// TODO remove:
	if s.sentryEnabled {
		sentry.CaptureMessage("It works!")
	}

	s.configure()
	s.setupLogging()

	s.databaseURL = viper.GetString("DBURL")
	s.port = viper.GetInt("PORT")

	return s.serve()
}

func (s *server) enableSentry() {
	sentryDSN := os.Getenv("SENTRY_DSN")
	if sentryDSN == "" {
		s.sentryEnabled = false
		return
	}

	err := sentry.Init(sentry.ClientOptions{
		Dsn:     sentryDSN,
		Release: fmt.Sprintf("%s-%s", s.appname, s.version),
	})
	if err != nil {
		log.Fatal().Err(err).Msg("sentry init failure")
	}
	s.sentryEnabled = true
}

func (s *server) serve() int {
	s.ctx, s.cancelFunc = context.WithCancel(context.Background())

	// signal watcher
	go func() {
		c := make(chan os.Signal, 1)
		signal.Ignore(syscall.SIGPIPE)
		signal.Notify(c, os.Interrupt, syscall.SIGTERM)
		// block and wait for signal
		sig := <-c
		s.log.Info().Msgf("signal received: %+v", sig)
		if s.cancelFunc != nil {
			// cancelling the main context will trigger a clean
			// shutdown.
			s.cancelFunc()
		}
	}()

	go s.serveUntilShutdown()

	for range s.ctx.Done() {
		//aforementioned clean shutdown upon main context
		//cancellation
	}
	s.cleanShutdown()
	return s.exitCode

}

func (s *server) cleanupForExit() {
	s.log.Info().Msg("cleaning up")
	// FIXME unimplemented
	// close database connections or whatever
}

func (s *server) cleanShutdown() {
	// initiate clean shutdown
	s.exitCode = 0
	ctxShutdown, shutdownCancel := context.WithTimeout(context.Background(), 5*time.Second)
	if err := s.httpServer.Shutdown(ctxShutdown); err != nil {
		s.log.Error().
			Err(err).
			Msg("server clean shutdown failed")
	}
	if shutdownCancel != nil {
		shutdownCancel()
	}

	s.cleanupForExit()

	if s.sentryEnabled {
		sentry.Flush(2 * time.Second)
	}
}

func (s *server) uptime() time.Duration {
	return time.Since(s.startupTime)
}

func (s *server) maintenance() bool {
	return viper.GetBool("MAINTENANCE_MODE")
}

func (s *server) configure() {
	viper.SetConfigName(s.appname)
	viper.SetConfigType("yaml")
	// path to look for the config file in:
	viper.AddConfigPath(fmt.Sprintf("/etc/%s", s.appname))
	// call multiple times to add many search paths:
	viper.AddConfigPath(fmt.Sprintf("$HOME/.config/%s", s.appname))
	//viper.SetEnvPrefix(strings.ToUpper(s.appname))
	viper.AutomaticEnv()

	viper.SetDefault("DEBUG", "false")
	viper.SetDefault("MAINTENANCE_MODE", "false")
	viper.SetDefault("PORT", "8080")
	viper.SetDefault("DBURL", "")

	if err := viper.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
			// Config file not found; ignore error if desired
		} else {
			// Config file was found but another error was produced
			log.Panic().
				Err(err).
				Msg("config file malformed")
		}
	}

	// if viper.GetBool("DEBUG") {
	//      pp.Print(viper.AllSettings())
	// }
}

func (s *server) setupLogging() {
	// always log in UTC
	zerolog.TimestampFunc = func() time.Time {
		return time.Now().UTC()
	}
	zerolog.SetGlobalLevel(zerolog.InfoLevel)

	tty := false
	if fileInfo, _ := os.Stdout.Stat(); (fileInfo.Mode() & os.ModeCharDevice) != 0 {
		tty = true
	}

	var writers []io.Writer

	if tty {
		// this does cool colorization for console/dev
		consoleWriter := zerolog.NewConsoleWriter(
			func(w *zerolog.ConsoleWriter) {
				// Customize time format
				w.TimeFormat = time.RFC3339Nano
			},
		)

		writers = append(writers, consoleWriter)
	} else {
		// log json in prod for the machines
		writers = append(writers, os.Stdout)
	}

	/*
		// this is how you log to a file, if you do that
		// sort of thing still
		logfile := viper.GetString("Logfile")
		if logfile != "" {
		    logfileDir := filepath.Dir(logfile)
		    err := goutil.Mkdirp(logfileDir)
		    if err != nil {
			    log.Error().Err(err).Msg("unable to create log dir")
		    }

		    hp.logfh, err = os.OpenFile(logfile, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
		    if err != nil {
			    panic("unable to open logfile: " + err.Error())
		    }

		    writers = append(writers, hp.logfh)
	*/

	multi := zerolog.MultiLevelWriter(writers...)
	logger := zerolog.New(multi).With().Timestamp().Logger().With().Caller().Logger()

	s.log = &logger
	//log.Logger = logger

	if viper.GetBool("debug") {
		zerolog.SetGlobalLevel(zerolog.DebugLevel)
		s.log.Debug().Bool("debug", true).Send()
	}

	s.identify()
}

func (s *server) identify() {
	s.log.Info().
		Str("appname", s.appname).
		Str("version", s.version).
		Str("buildarch", s.buildarch).
		Msg("starting")
}