feat: SystemD socket

Created a systemd socket unit will be responsible to listen the
connection, and when something connects to it, the daemon will
initialize the service.

Hooks were also updated to have a smooth transition between versions
installations to avoid any downtime.

Additionally, Golang code was updated to read the socket created, and
deal with service shutdown.

.goreleaser.yaml

@@ -49,6 +49,8 @@ nfpms:
     contents:
       - src: "env/debian/movies.service"
         dst: "/lib/systemd/system/movies.service"
+      - src: "env/debian/movies.socket"
+        dst: "/lib/systemd/system/movies.socket"
       - src: "env/debian/movies.conf"
         dst: "/etc/default/movies"
         type: config

cmd/movies/main.go

@@ -1,9 +1,13 @@
 package main
 
 import (
+	"context"
 	"os"
+	"os/signal"
 	"path/filepath"
+	"time"
 
+	"github.com/coreos/go-systemd/v22/activation"
 	"github.com/labstack/echo/v4"
 	mw "github.com/labstack/echo/v4/middleware"
 	glog "github.com/labstack/gommon/log"
@@ -19,6 +23,8 @@ const (
 	dbPathEnv = "MOVIES_DB_PATH"
 )
 
+const timeout = 10 * time.Second
+
 func main() {
 	e := echo.New()
 	e.HidePort = true
@@ -52,7 +58,35 @@ func main() {
 	// Start server
 	e.Logger.Infof("%s service", appName)
 
-	if err := e.Start(appAddr); err != nil {
+	go func() {
+		if err := start(e, appAddr); err != nil {
+			e.Logger.Info("shutting down the service")
+		}
+	}()
+
+	// Graceful shutdown
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, os.Interrupt)
+
+	<-quit
+
+	ctx, cancel := context.WithTimeout(context.TODO(), timeout)
+	defer cancel()
+
+	if err := e.Shutdown(ctx); err != nil {
 		e.Logger.Fatal(err)
 	}
 }
+
+func start(e *echo.Echo, host string) error {
+	listeners, err := activation.Listeners()
+	if err != nil {
+		return nil
+	}
+
+	if len(listeners) > 0 {
+		e.Listener = listeners[0]
+	}
+
+	return e.Start(host)
+}

env/debian/movies.service

@@ -1,6 +1,8 @@
 [Unit]
 Description=Manages movie collection throught API
 Documentation="https://github.com/faabiosr/go-movies-demo"
+After=network.target
+Requires=movies.socket
 
 [Service]
 EnvironmentFile=/etc/default/movies

env/debian/movies.socket

@@ -0,0 +1,11 @@
+[Unit]
+Description=Manages movie collection throught API
+Documentation="https://github.com/faabiosr/go-movies-demo"
+
+[Socket]
+ListenStream=8000
+SocketUser=movies-demo
+SocketGroup=movies-demo
+
+[Install]
+WantedBy=sockets.target

env/debian/post-install.sh

@@ -5,6 +5,7 @@ set -e
 MOVIES_DB_PATH=/var/lib/movies-demo
 MOVIES_USER=movies-demo
 MOVIES_SERVICE=movies.service
+MOVIES_SOCKET=movies.socket
 
 if [ "$1" = "configure" ]; then
     # creating user and group
@@ -30,16 +31,24 @@ if [ "$1" = "configure" ]; then
         deb-systemd-helper update-state $MOVIES_SERVICE >/dev/null || true
     fi
 
+    # enable systemd socket
+    deb-systemd-helper unmask $MOVIES_SOCKET >/dev/null || true
+
+    if deb-systemd-helper --quiet was-enabled $MOVIES_SOCKET; then
+        deb-systemd-helper enable $MOVIES_SOCKET >/dev/null || true
+    else
+        deb-systemd-helper update-state $MOVIES_SOCKET >/dev/null || true
+    fi
+
     # starting service
     if [ -d /run/systemd/system ]; then
         systemctl --system daemon-reload >/dev/null || true
 
         if [ -n "$2" ]; then
-            _dh_action=restart
+            deb-systemd-invoke restart $MOVIES_SERVICE >/dev/null || true
         else
-            _dh_action=start
+            deb-systemd-invoke start $MOVIES_SOCKET >/dev/null || true
         fi
 
-        deb-systemd-invoke $_dh_action $MOVIES_SERVICE >/dev/null || true
     fi
 fi

env/debian/post-remove.sh

@@ -4,6 +4,7 @@ set -e
 
 MOVIES_DB_PATH=/var/lib/movies-demo
 MOVIES_SERVICE=movies.service
+MOVIES_SOCKET=movies.socket
 
 if [ "$1" = "remove" ]; then
     if [ -f "$MOVIES_DB_PATH/catalog.db" ]; then
@@ -18,11 +19,20 @@ if [ "$1" = "remove" ]; then
         systemctl --system daemon-reload >/dev/null || true
     fi
 
+    deb-systemd-helper mask $MOVIES_SERVICE $MOVIES_SOCKET >/dev/null || true
+fi
+
+if [ "$1" = "upgrade" ]; then
+    # disabling service
+    if [ -d /run/systemd/system ]; then
+        systemctl --system daemon-reload >/dev/null || true
+    fi
+
     deb-systemd-helper mask $MOVIES_SERVICE >/dev/null || true
 fi
 
 if [ "$1" = "purge" ]; then
     # disabling service
-    deb-systemd-helper purge $MOVIES_SERVICE >/dev/null || true
-    deb-systemd-helper unmask $MOVIES_SERVICE >/dev/null || true
+    deb-systemd-helper purge $MOVIES_SERVICE $MOVIES_SOCKET >/dev/null || true
+    deb-systemd-helper unmask $MOVIES_SERVICE $MOVIES_SOCKET >/dev/null || true
 fi

env/debian/pre-remove.sh

@@ -3,8 +3,18 @@
 set -e
 
 MOVIES_SERVICE=movies.service
+MOVIES_SOCKET=movies.socket
 
-# stopping service
-if [ -d /run/systemd/system ]; then
-    deb-systemd-invoke stop $MOVIES_SERVICE >/dev/null || true
+if [ "$1" = "remove" ]; then
+    # stopping service and socket
+    if [ -d /run/systemd/system ]; then
+        deb-systemd-invoke stop $MOVIES_SERVICE $MOVIES_SOCKET >/dev/null || true
+    fi
+fi
+
+if [ "$1" = "upgrade" ]; then
+    # stopping service
+    if [ -d /run/systemd/system ]; then
+        deb-systemd-invoke stop $MOVIES_SERVICE >/dev/null || true
+    fi
 fi

go.mod

@@ -3,6 +3,7 @@ module github.com/faabiosr/go-movies-demo
 go 1.21
 
 require (
+	github.com/coreos/go-systemd/v22 v22.5.0
 	github.com/go-ozzo/ozzo-validation/v4 v4.3.0
 	github.com/gofrs/uuid/v5 v5.0.0
 	github.com/labstack/echo/v4 v4.11.2

go.sum

@@ -1,10 +1,13 @@
 github.com/asaskevich/govalidator v0.0.0-20200108200545-475eaeb16496 h1:zV3ejI06GQ59hwDQAvmK1qxOQGB3WuVTRoY0okPTAv0=
 github.com/asaskevich/govalidator v0.0.0-20200108200545-475eaeb16496/go.mod h1:oGkLhpf+kjZl6xBf758TQhh5XrAeiJv/7FRz/2spLIg=
+github.com/coreos/go-systemd/v22 v22.5.0 h1:RrqgGjYQKalulkV8NGVIfkXQf6YYmOyiJKk8iXXhfZs=
+github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/go-ozzo/ozzo-validation/v4 v4.3.0 h1:byhDUpfEwjsVQb1vBunvIjh2BHQ9ead57VkAEY4V+Es=
 github.com/go-ozzo/ozzo-validation/v4 v4.3.0/go.mod h1:2NKgrcHl3z6cJs+3Oo940FPRiTzuqKbvfrL2RxCj6Ew=
+github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/gofrs/uuid/v5 v5.0.0 h1:p544++a97kEL+svbcFbCQVM9KFu0Yo25UoISXGNNH9M=
 github.com/gofrs/uuid/v5 v5.0.0/go.mod h1:CDOjlDMVAtN56jqyRUZh58JT31Tiw7/oQyEXZV+9bD8=
 github.com/golang-jwt/jwt v3.2.2+incompatible h1:IfV12K8xAKAnZqdXVzCZ+TOjboZ2keLg81eXfW3O+oY=