option to disable file watcher (#2485)

Co-authored-by: Sergey Galkin <v.sergey.galkin@reddit.com>

config/config.go

@@ -41,6 +41,8 @@ type Options struct {
 
 	// for alternative data
 	Context context.Context
+
+	WithWatcherDisabled bool
 }
 
 type Option func(o *Options)

config/default.go

@@ -37,7 +37,9 @@ func newConfig(opts ...Option) (Config, error) {
 	if err != nil {
 		return nil, err
 	}
+	if !c.opts.WithWatcherDisabled {
 		go c.run()
+	}
 
 	return &c, nil
 }
@@ -53,7 +55,12 @@ func (c *config) Init(opts ...Option) error {
 
 	// default loader uses the configured reader
 	if c.opts.Loader == nil {
-		c.opts.Loader = memory.NewLoader(memory.WithReader(c.opts.Reader))
+		loaderOpts := []loader.Option{memory.WithReader(c.opts.Reader)}
+		if c.opts.WithWatcherDisabled {
+			loaderOpts = append(loaderOpts, memory.WithWatcherDisabled())
+		}
+
+		c.opts.Loader = memory.NewLoader(loaderOpts...)
 	}
 
 	err := c.opts.Loader.Load(c.opts.Source...)

config/loader/loader.go

@@ -48,6 +48,8 @@ type Options struct {
 
 	// for alternative data
 	Context context.Context
+
+	WithWatcherDisabled bool
 }
 
 type Option func(o *Options)

config/loader/memory/memory.go

@@ -323,8 +323,10 @@ func (m *memory) Load(sources ...source.Source) error {
 		m.sets = append(m.sets, set)
 		idx := len(m.sets) - 1
 		m.Unlock()
+		if !m.opts.WithWatcherDisabled {
 			go m.watch(idx, source)
 		}
+	}
 
 	if err := m.reload(); err != nil {
 		gerrors = append(gerrors, err.Error())
@@ -338,6 +340,10 @@ func (m *memory) Load(sources ...source.Source) error {
 }
 
 func (m *memory) Watch(path ...string) (loader.Watcher, error) {
+	if m.opts.WithWatcherDisabled {
+		return nil, errors.New("watcher is disabled")
+	}
+
 	value, err := m.Get(path...)
 	if err != nil {
 		return nil, err
@@ -449,8 +455,10 @@ func NewLoader(opts ...loader.Option) loader.Loader {
 
 	for i, s := range options.Source {
 		m.sets[i] = &source.ChangeSet{Source: s.String()}
+		if !options.WithWatcherDisabled {
 			go m.watch(i, s)
 		}
+	}
 
 	return m
 }

config/loader/memory/options.go

@@ -19,3 +19,9 @@ func WithReader(r reader.Reader) loader.Option {
 		o.Reader = r
 	}
 }
+
+func WithWatcherDisabled() loader.Option {
+	return func(o *loader.Options) {
+		o.WithWatcherDisabled = true
+	}
+}

config/options.go

@@ -26,3 +26,9 @@ func WithReader(r reader.Reader) Option {
 		o.Reader = r
 	}
 }
+
+func WithWatcherDisabled() Option {
+	return func(o *Options) {
+		o.WithWatcherDisabled = true
+	}
+}