gracefully shutdown server

cmd/server.go

@@ -3,6 +3,8 @@ package cmd
 import (
 	"alertmanager/config"
 	"alertmanager/server"
+	"fmt"
+	"os"
 
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -19,19 +21,28 @@ func serverCommandRunE(cmd *cobra.Command, args []string) error {
 	sPort, _ := cmd.Flags().GetInt("server-port")
 	mPort, _ := cmd.Flags().GetInt("metric-port")
 	mgmtPort, _ := cmd.Flags().GetInt("meanagement-port")
-	// _, _ := cmd.Flags().GetString("config-file")
+	cFile, _ := cmd.Flags().GetString("config-file")
 
 	log := logrus.New()
 	err := setLogLevelE(log, ll)
 	if err != nil {
 		return err
 	}
 
+	b, err := os.ReadFile(cFile)
+	if err != nil {
+		return fmt.Errorf("cannot read config file; %s", err)
+	}
+	amConfig, err := config.ValidateAndLoad(b)
+	if err != nil {
+		return fmt.Errorf("validation failed: please refer to template; %s", err)
+	}
+
 	var s = server.Server{
 		ServerPort:     sPort,
 		MetricsPort:    mPort,
 		ManagementPort: mgmtPort,
-		Config:         &config.AlertManagerConfig{},
+		Config:         amConfig,
 		Log:            log,
 	}
 
@@ -43,8 +54,9 @@ func init() {
 	rootCmd.AddCommand(serverCmd)
 
 	serverCmd.Flags().Int("server-port", 8081, "Port to listen on")
-	serverCmd.Flags().Int("metric-port", 8082, "metrics port to listen on")
-	serverCmd.Flags().Int("management-port", 8083, "management port to listen on")
+	// todo set up management api and metrics endpoint
+	// serverCmd.Flags().Int("metric-port", 8082, "metrics port to listen on")
+	// serverCmd.Flags().Int("management-port", 8083, "management port to listen on")
 	serverCmd.Flags().String("config-file", "./alert-manager-config.yml", "Path to alert config")
 	serverCmd.Flags().String("log-level", DEFAULT_LOG_LEVEL, "log-level for alertmanager; options INFO|DEBUG|ERROR")
 }

config/config.go

@@ -67,7 +67,7 @@ func ValidateAndLoad(b []byte) (AlertManagerConfig, error) {
 
 	if len(b) > 0 && amConfig.AlertPipelines == nil {
 		return AlertManagerConfig{},
-			fmt.Errorf("unable to load config, please check format; %s", err)
+			fmt.Errorf("unable to load config, please check format")
 	}
 	// todo:
 	// do better validation

scratchpad.md

@@ -5,10 +5,10 @@
     - --auth-config
 - Use [net/http]
   - needs 2 min endpoints
-    - POST / (for getting webhook)
+    - POST /webhook (for getting webhook)
     - POST /~/reload to reload config
     - GET /~/config to get current loaded config
-    - GET /health
+    - GET /ping
 - Use logrus for logging
 - Tests
 

server/handler.go

@@ -0,0 +1,7 @@
+package server
+
+import "github.com/gofiber/fiber/v2"
+
+func alertWebhookHandler(c *fiber.Ctx) error {
+	return c.SendString("pong")
+}

server/server.go

@@ -3,7 +3,11 @@ package server
 import (
 	"alertmanager/config"
 	"fmt"
+	"os"
+	"os/signal"
 	"strconv"
+	"sync"
+	"time"
 
 	"github.com/sirupsen/logrus"
 
@@ -15,7 +19,7 @@ type Server struct {
 	ServerPort     int
 	MetricsPort    int
 	ManagementPort int
-	Config         *config.AlertManagerConfig
+	Config         config.AlertManagerConfig
 	Log            *logrus.Logger
 }
 
@@ -24,12 +28,38 @@ func (s *Server) Start() error {
 
 	app := fiber.New()
 
+	// handle gradeful app shutdown
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt) // SIGINT
+
+	var serverShutDownWG sync.WaitGroup // wait for the server to shutdown cleanly
+
+	// shutdown server upon SIGINT and signal the waitgroup
+	go func() {
+		<-c
+
+		s.Log.Info("shutting down server cleanly; please wait :)")
+		serverShutDownWG.Add(1)
+		defer serverShutDownWG.Done()
+
+		_ = app.ShutdownWithTimeout(time.Second * 30)
+	}()
+
+	// request logger middlewear
+	// should be okay as long the server is low-volume
+	// maybe we can configure to log only bad / failed reqs
 	app.Use(logger.New())
 
 	app.Get("/ping", func(c *fiber.Ctx) error {
 		return c.SendString("pong")
 	})
 
-	app.Listen(":" + strconv.Itoa(s.ServerPort))
+	app.Post("/webhook/", alertWebhookHandler)
+
+	if err := app.Listen(":" + strconv.Itoa(s.ServerPort)); err != nil {
+		s.Log.Error("server: unable to start server", err)
+	}
+
+	serverShutDownWG.Wait()
 	return nil
 }