Initial module commit

Author: bgv

go.mod

@@ -0,0 +1,9 @@
+module github.com/codechimp-io/graceful
+
+go 1.12
+
+require (
+	github.com/cloudflare/tableflip v1.0.0
+	github.com/codechimp-io/log v1.0.3
+	github.com/oklog/run v1.0.0
+)

graceful.go

@@ -0,0 +1,136 @@
+package graceful
+
+import (
+	"context"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/cloudflare/tableflip"
+	"github.com/codechimp-io/log"
+	"github.com/oklog/run"
+)
+
+var ShutdownTimeout = 3 * time.Second
+
+// Run graceful http server
+func Run(server *http.Server, pidfile string) {
+	// configure graceful restart
+	upg, err := tableflip.New(tableflip.Options{
+		PIDFile: pidfile,
+	})
+	if err != nil {
+		log.Errorf("Creating graceful upgrader failed: %v", err)
+	}
+	defer upg.Stop()
+
+	// Do an upgrade on SIGHUP
+	go func() {
+		sig := make(chan os.Signal, 1)
+		signal.Notify(sig, syscall.SIGHUP)
+		for range sig {
+			log.Info("Received SIGHUP, restaring gracefully...")
+			err := upg.Upgrade()
+			if err != nil {
+				log.Errorf("Upgrade failed: %v", err)
+			}
+		}
+	}()
+
+	var group run.Group
+
+	// Set up http server
+	{
+		ln, err := upg.Fds.Listen("tcp", server.Addr)
+		if err != nil {
+			log.Fatalf("Error creating new listener: %s", err)
+		}
+
+		group.Add(
+			func() error {
+				log.Infof("Listening on [%s] with pid [%d]", server.Addr, os.Getpid())
+
+				return server.Serve(ln)
+			},
+			func(e error) {
+				if e != nil {
+					log.Fatalf("Failed to start HTTP Server: %v", e)
+				}
+
+				log.Info("Shutting HTTP Server down")
+
+				ctx := context.Background()
+				if ShutdownTimeout > 0 {
+					var cancel context.CancelFunc
+					ctx, cancel = context.WithTimeout(ctx, ShutdownTimeout)
+					defer cancel()
+				}
+
+				err := server.Shutdown(ctx)
+				if err != nil {
+					log.Errorf("Error shutting down HTTP server: %s", err)
+				}
+
+				_ = server.Close()
+			},
+		)
+	}
+
+	// Setup signal handler
+	{
+		var (
+			cancelInterrupt = make(chan struct{})
+			ch              = make(chan os.Signal, 2)
+		)
+		defer close(ch)
+
+		group.Add(
+			func() error {
+				signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM)
+
+				select {
+				case sig := <-ch:
+					switch sig {
+					case syscall.SIGINT:
+						log.Info("Received SIGINT, exiting gracefully...")
+					case syscall.SIGTERM:
+						log.Info("Received SIGTERM, exiting gracefully...")
+					}
+
+				case <-cancelInterrupt:
+				}
+
+				return nil
+			},
+			func(e error) {
+				close(cancelInterrupt)
+				signal.Stop(ch)
+			},
+		)
+	}
+
+	{
+		group.Add(
+			func() error {
+				// Tell the parent we are ready
+				_ = upg.Ready()
+
+				// Wait for children to be ready
+				// (or application shutdown)
+				<-upg.Exit()
+
+				return nil
+			},
+			func(e error) {
+				upg.Stop()
+			},
+		)
+	}
+
+	err = group.Run()
+	if err != nil {
+		log.Fatalf("Error starting service: %s", err)
+	}
+}