[ws-daemon] Refactor watch of configuration file

Author: aledbf

components/ws-daemon/cmd/run.go

@@ -29,6 +29,7 @@ import (
 	common_grpc "github.com/gitpod-io/gitpod/common-go/grpc"
 	"github.com/gitpod-io/gitpod/common-go/log"
 	"github.com/gitpod-io/gitpod/common-go/pprof"
+	"github.com/gitpod-io/gitpod/common-go/watch"
 	"github.com/gitpod-io/gitpod/ws-daemon/pkg/config"
 	"github.com/gitpod-io/gitpod/ws-daemon/pkg/daemon"
 )
@@ -128,7 +129,27 @@ var runCmd = &cobra.Command{
 			log.WithError(err).Fatal("cannot start daemon")
 		}
 
-		go config.Watch(configFile, dmn.ReloadConfig)
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		err = watch.File(ctx, configFile, func() {
+			ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+			defer cancel()
+
+			cfg, err := config.Read(configFile)
+			if err != nil {
+				log.WithError(err).Warn("cannot reload configuration")
+				return
+			}
+
+			err = dmn.ReloadConfig(ctx, &cfg.Daemon)
+			if err != nil {
+				log.WithError(err).Warn("cannot reload configuration")
+			}
+		})
+		if err != nil {
+			log.WithError(err).Fatal("cannot start watch of configuration file")
+		}
 
 		// run until we're told to stop
 		sigChan := make(chan os.Signal, 1)

components/ws-daemon/pkg/config/config.go

@@ -6,21 +6,15 @@ package config
 
 import (
 	"bytes"
-	"context"
-	"crypto/sha256"
 	"crypto/tls"
-	"encoding/hex"
 	"encoding/json"
-	"io"
 	"os"
-	"time"
 
 	"golang.org/x/xerrors"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
 
 	common_grpc "github.com/gitpod-io/gitpod/common-go/grpc"
-	"github.com/gitpod-io/gitpod/common-go/log"
 	"github.com/gitpod-io/gitpod/ws-daemon/pkg/daemon"
 )
 
@@ -41,63 +35,6 @@ func Read(fn string) (*Config, error) {
 	return &cfg, nil
 }
 
-// watchConfig watches the configuration file and if changed reloads the static layer
-func Watch(fn string, cb func(context.Context, *daemon.Config) error) {
-	hashConfig := func() (hash string, err error) {
-		f, err := os.Open(fn)
-		if err != nil {
-			return "", err
-		}
-		defer f.Close()
-
-		h := sha256.New()
-		_, err = io.Copy(h, f)
-		if err != nil {
-			return "", err
-		}
-
-		return hex.EncodeToString(h.Sum(nil)), nil
-	}
-	reloadConfig := func() error {
-		cfg, err := Read(fn)
-		if err != nil {
-			return err
-		}
-
-		ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-		defer cancel()
-
-		return cb(ctx, &cfg.Daemon)
-	}
-
-	var (
-		tick    = time.NewTicker(30 * time.Second)
-		oldHash string
-	)
-	defer tick.Stop()
-	for range tick.C {
-		currentHash, err := hashConfig()
-		if err != nil {
-			log.WithError(err).Warn("cannot check if config has changed")
-		}
-
-		if oldHash == "" {
-			oldHash = currentHash
-		}
-		if currentHash == oldHash {
-			continue
-		}
-		oldHash = currentHash
-
-		err = reloadConfig()
-		if err == nil {
-			log.Info("configuration was updated - reloaded static layer config")
-		} else {
-			log.WithError(err).Error("cannot reload config - config hot reloading did not work")
-		}
-	}
-}
-
 type Config struct {
 	Daemon             daemon.Config `json:"daemon"`
 	Service            AddrTLS       `json:"service"`