fairwind/application.go

package fairwind

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

type ApplicationModule interface {
	Name() string
	Start() error
	Stop() error
}

type ApplicationModuleBuilder func(ctx context.Context, log *Log) (ApplicationModule, error)

type Application struct {
	ctx     context.Context
	cancel  func()
	log     *Log
	modules []ApplicationModule
}

func Run(builders ...ApplicationModuleBuilder) {
	ctx, cancel := context.WithCancel(context.Background())
	log := NewLog(NewLogFormatterJSON())

	modules := []ApplicationModule{}
	for _, builder := range builders {
		module, err := builder(ctx, log)
		if err != nil {
			log.Error("can't build module", LogValue("name", module.Name()), LogError(err))
			cancel()
			return
		}

		modules = append(modules, module)
	}

	this := &Application{
		ctx:     ctx,
		cancel:  cancel,
		log:     log,
		modules: modules,
	}

	this.log.Information("starting application")
	this.startup()

	channel := make(chan os.Signal, 1)
	signal.Notify(channel, syscall.SIGTERM, syscall.SIGINT)
	<-channel

	this.log.Information("stopping application")
	this.cancel()
	this.shutdown()
}

func (this *Application) startup() {
	waitGroup := sync.WaitGroup{}
	waitGroup.Add(len(this.modules))

	start := func(log *Log, module ApplicationModule) {
		log.Information("starting module", LogValue("module", module.Name()))

		err := module.Start()
		if err != nil {
			log.Error("error starting module", LogValue("module", module.Name()), LogError(err))
		} else {
			log.Information("module started", LogValue("module", module.Name()))
		}

		waitGroup.Done()
	}
	for _, module := range this.modules {
		go start(this.log, module)
	}

	waitGroup.Wait()
}

func (this *Application) shutdown() {
	waitGroup := sync.WaitGroup{}
	waitGroup.Add(len(this.modules))

	stop := func(log *Log, module ApplicationModule) {
		log.Information("stopping module", LogValue("module", module.Name()))

		err := module.Stop()
		if err != nil {
			log.Error("error stopping module", LogValue("module", module.Name()), LogError(err))
		} else {
			log.Information("module stopped", LogValue("module", module.Name()))
		}

		waitGroup.Done()
	}
	for _, module := range this.modules {
		go stop(this.log, module)
	}

	waitGroup.Wait()
}