fsnotify file watcher

Makefile

@@ -29,6 +29,9 @@ test:
 lint:
 	golangci-lint run ./...
 
+format:
+	go fmt ./...
+
 proto:
 	@ if ! which protoc > /dev/null; then \
 		echo "error: protoc not installed" >&2; \

blazar.sample.toml

@@ -25,7 +25,7 @@ http-port = 1234
 grpc-port = 5678
 
 [watchers]
-# Interval to poll for upgrade-info.json
+# Interval to poll for upgrade-info.json. If zero (0) blazar will utilize fsnotify to watch the file, instaead of polling at given interval.
 # Interpreted as Go's time.Duration
 upgrade-info-interval = "300ms"
 # Interval to poll the chain for the last height

internal/pkg/chain_watcher/upgrades_info_watcher.go

@@ -29,7 +29,19 @@ type NewUpgradeInfo struct {
 
 func NewUpgradeInfoWatcher(ctx context.Context, upgradeInfoFilePath string, interval time.Duration) (*UpgradesInfoWatcher, error) {
 	logger := log.FromContext(ctx)
-	exists, fw, err := file_watcher.NewFileWatcher(logger, upgradeInfoFilePath, interval)
+	var (
+		exists bool
+		fw     file_watcher.FileWatcher
+		err    error
+	)
+
+	if interval == 0 {
+		exists, fw, err = file_watcher.NewNotifyFileWatcher(logger, upgradeInfoFilePath)
+		logger.Info("Selected notify file watcher")
+	} else {
+		exists, fw, err = file_watcher.NewPollingFileWatcher(logger, upgradeInfoFilePath, interval)
+		logger.Info("Selected polling file watcher")
+	}
 	if err != nil {
 		return nil, errors.Wrapf(err, "error creating file watcher for %s", upgradeInfoFilePath)
 	}
@@ -54,7 +66,7 @@ func NewUpgradeInfoWatcher(ctx context.Context, upgradeInfoFilePath string, inte
 
 	go func() {
 		for {
-			newEvent := <-fw.ChangeEvents
+			newEvent := <-fw.ChangeEvents()
 			if newEvent.Error != nil {
 				panic(errors.Wrapf(newEvent.Error, "upgrade info watcher's file watcher observed an error"))
 			}

internal/pkg/config/config.go

@@ -460,8 +460,8 @@ func (cfg *Config) ValidateAll() error {
 		return errors.New("http-port cannot be 0")
 	}
 
-	if cfg.Watchers.UIInterval <= 0 {
-		return errors.New("watchers.upgrade-info-interval cannot be less than or equal to 0")
+	if cfg.Watchers.UIInterval < 0 {
+		return errors.New("watchers.upgrade-info-interval cannot be less than 0")
 	}
 
 	if cfg.Watchers.HInterval < 0 {

internal/pkg/daemon/daemon_test.go

@@ -523,7 +523,7 @@ func generateConfig(t *testing.T, tempDir, serviceName string, grpcPort, cometbf
 		UpgradeMode:    config.UpgradeInComposeFile,
 		Host:           "dummy",
 		Watchers: config.Watchers{
-			UIInterval: time.Millisecond * 5,
+			UIInterval: 0, // NotifyFileWatcher is enabled
 			HInterval:  time.Second * 0,
 			HTimeout:   20 * time.Second,
 			UPInterval: time.Minute * 5,

internal/pkg/file_watcher/file_watcher.go

@@ -1,12 +1,6 @@
 package file_watcher
 
-import (
-	"os"
-	"time"
-
-	"blazar/internal/pkg/errors"
-	"blazar/internal/pkg/log"
-)
+import "os"
 
 type FileChangeEvent int
 
@@ -21,90 +15,15 @@ type NewFileChangeEvent struct {
 	Error error
 }
 
-type FileWatcher struct {
-	// full path to a watched file
-	lastModTime  time.Time
-	exists       bool
-	ChangeEvents <-chan NewFileChangeEvent
-	cancel       chan<- struct{}
+type FileWatcher interface {
+	ChangeEvents() <-chan NewFileChangeEvent
+	Cancel()
 }
 
-// Returns if the file exists, file watcher, error
-func NewFileWatcher(logger *log.MultiLogger, filepath string, interval time.Duration) (bool, *FileWatcher, error) {
-	// In case file doesn't exist, modTime will be "zero"
-	// so we can still use it to check for "file change"
-	// as modTime of created file will be be greater than this
-	initExists, initModTime, err := getFileStatus(filepath)
-	if err != nil {
-		return false, nil, errors.Wrapf(err, "failed to check %s status", filepath)
+func fileExists(file string) (bool, error) {
+	_, err := os.Stat(file)
+	if os.IsNotExist(err) {
+		return false, nil
 	}
-
-	events := make(chan NewFileChangeEvent)
-	cancel := make(chan struct{})
-
-	fw := &FileWatcher{
-		lastModTime:  initModTime,
-		exists:       initExists,
-		ChangeEvents: events,
-		cancel:       cancel,
-	}
-
-	go func() {
-		ticker := time.NewTicker(interval)
-		for {
-			select {
-			case <-ticker.C:
-				var newEvent NewFileChangeEvent
-				exists, modTime, err := getFileStatus(filepath)
-				if err != nil {
-					newEvent.Error = err
-				} else {
-					if exists != fw.exists {
-						if exists {
-							fw.lastModTime = modTime
-							newEvent.Event = FileCreated
-						} else {
-							newEvent.Event = FileRemoved
-						}
-						fw.exists = exists
-					} else if modTime.After(fw.lastModTime) {
-						fw.lastModTime = modTime
-						newEvent.Event = FileModified
-					}
-				}
-				select {
-				case events <- newEvent:
-				// to prevent deadlock with events channel
-				case <-cancel:
-					logger.Debug("File watcher exiting")
-					return
-				}
-			// this isn't necessary since we exit in the above select statement
-			// but this will help in early exit in case cancel is called before the ticker fires
-			case <-cancel:
-				logger.Debug("File watcher exiting")
-				return
-			}
-		}
-	}()
-	return initExists, fw, nil
-}
-
-func (fw *FileWatcher) Cancel() {
-	fw.cancel <- struct{}{}
-}
-
-// Checks if the file exists and returns the timestamp of the last modification
-// returns exists, modTime, error
-func getFileStatus(file string) (bool, time.Time, error) {
-	stat, err := os.Stat(file)
-
-	switch {
-	case os.IsNotExist(err):
-		return false, time.Time{}, nil
-	case err != nil:
-		return false, time.Time{}, err
-	}
-
-	return true, stat.ModTime(), nil
+	return err == nil, err
 }