wip: optimize graceful shutdown

examples/graceful/main.go

@@ -4,8 +4,10 @@ import (
 	"context"
 	"net/http"
 	"sync"
+	"syscall"
 	"time"
 
+	"github.com/foomo/keel/interfaces"
 	"github.com/foomo/keel/service"
 	"go.uber.org/zap"
 
@@ -15,6 +17,7 @@ import (
 
 func main() {
 	svr := keel.NewServer(
+		//keel.WithLogger(zap.NewExample()),
 		keel.WithHTTPZapService(true),
 		keel.WithHTTPViperService(true),
 		keel.WithHTTPPrometheusService(true),
@@ -28,15 +31,70 @@ func main() {
 	// create demo service
 	svs := http.NewServeMux()
 	svs.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		l.Info("handling request...")
+		time.Sleep(3 * time.Second)
 		w.WriteHeader(http.StatusOK)
 		_, _ = w.Write([]byte("OK"))
+		l.Info("... handled request")
 	})
 
 	svr.AddService(
 		service.NewHTTP(l, "demo", "localhost:8080", svs),
 	)
 
-	svr.Run()
+	svr.AddCloser(interfaces.CloseFunc(func(ctx context.Context) error {
+		l.Info("custom closer")
+		return nil
+	}))
+
+	go svr.Run()
+	time.Sleep(1 * time.Second)
+	l.Info("1. starting test")
+
+	{
+		l.Info("2. checking healthz")
+		readiness(l, "http://localhost:9400/healthz/readiness")
+	}
+
+	go func() {
+		l.Info("2. sending request")
+		if r, err := http.Get("http://localhost:8080"); err != nil {
+			l.Fatal(err.Error())
+		} else {
+			l.Info("  /", zap.Int("status", r.StatusCode))
+		}
+	}()
+	time.Sleep(100 * time.Millisecond)
+
+	l.Info("3. sending shutdown signal")
+	if err := syscall.Kill(syscall.Getpid(), syscall.SIGTERM); err != nil {
+		l.Fatal(err.Error())
+	}
+
+	{
+		l.Info("2. checking healthz")
+		readiness(l, "http://localhost:9400/healthz/readiness")
+	}
+
+	l.Info("4. waiting for shutdown")
+	time.Sleep(10 * time.Second)
+	l.Info("  done")
+}
+
+func readiness(l *zap.Logger, url string) {
+	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	defer cancel()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		l.Error(err.Error())
+		return
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		l.Error(err.Error())
+		return
+	}
+	l.Info(url, zap.Int("status", resp.StatusCode))
 }
 
 func waitGroup(ctx context.Context, l *zap.Logger) {

interfaces/closer.go

@@ -4,6 +4,14 @@ import (
 	"context"
 )
 
+type CloseHandler struct {
+	Value func(ctx context.Context) error
+}
+
+func (r CloseHandler) Close(ctx context.Context) error {
+	return r.Value(ctx)
+}
+
 // Closer interface
 type Closer interface {
 	Close()
@@ -23,3 +31,9 @@ type CloserWithContext interface {
 type ErrorCloserWithContext interface {
 	Close(ctx context.Context) error
 }
+
+func CloseFunc(v func(ctx context.Context) error) CloseHandler {
+	return CloseHandler{
+		Value: v,
+	}
+}

server.go

@@ -65,7 +65,7 @@ type Server struct {
 func NewServer(opts ...Option) *Server {
 	inst := &Server{
 		shutdownTimeout: 30 * time.Second,
-		shutdownSignals: []os.Signal{os.Interrupt, syscall.SIGTERM},
+		shutdownSignals: []os.Signal{syscall.SIGTERM},
 		syncReadmers:    []interfaces.Readmer{},
 		syncProbes:      map[healthz.Type][]interface{}{},
 		ctx:             context.Background(),