Add watch options

registry/consul_registry.go

@@ -279,8 +279,8 @@ func (c *consulRegistry) ListServices() ([]*Service, error) {
 	return services, nil
 }
 
-func (c *consulRegistry) Watch() (Watcher, error) {
-	return newConsulWatcher(c)
+func (c *consulRegistry) Watch(opts ...WatchOption) (Watcher, error) {
+	return newConsulWatcher(c, opts...)
 }
 
 func (c *consulRegistry) String() string {

registry/consul_watcher.go

@@ -10,6 +10,7 @@ import (
 
 type consulWatcher struct {
 	r        *consulRegistry
+	wo       WatchOptions
 	wp       *watch.Plan
 	watchers map[string]*watch.Plan
 
@@ -20,9 +21,15 @@ type consulWatcher struct {
 	services map[string][]*Service
 }
 
-func newConsulWatcher(cr *consulRegistry) (Watcher, error) {
+func newConsulWatcher(cr *consulRegistry, opts ...WatchOption) (Watcher, error) {
+	var wo WatchOptions
+	for _, o := range opts {
+		o(&wo)
+	}
+
 	cw := &consulWatcher{
 		r:        cr,
+		wo:       wo,
 		exit:     make(chan bool),
 		next:     make(chan *Result, 10),
 		watchers: make(map[string]*watch.Plan),
@@ -185,6 +192,12 @@ func (cw *consulWatcher) handle(idx uint64, data interface{}) {
 
 	// add new watchers
 	for service, _ := range services {
+		// Filter on watch options
+		// wo.Service: Only watch services we care about
+		if len(cw.wo.Service) > 0 && service != cw.wo.Service {
+			continue
+		}
+
 		if _, ok := cw.watchers[service]; ok {
 			continue
 		}

registry/mdns/mdns.go

@@ -297,8 +297,14 @@ func (m *mdnsRegistry) ListServices() ([]*registry.Service, error) {
 	return services, nil
 }
 
-func (m *mdnsRegistry) Watch() (registry.Watcher, error) {
+func (m *mdnsRegistry) Watch(opts ...registry.WatchOption) (registry.Watcher, error) {
+	var wo registry.WatchOptions
+	for _, o := range opts {
+		o(&wo)
+	}
+
 	md := &mdnsWatcher{
+		wo:   wo,
 		ch:   make(chan *mdns.ServiceEntry, 32),
 		exit: make(chan struct{}),
 	}

registry/mdns/watcher.go

@@ -9,6 +9,7 @@ import (
 )
 
 type mdnsWatcher struct {
+	wo   registry.WatchOptions
 	ch   chan *mdns.ServiceEntry
 	exit chan struct{}
 }
@@ -26,6 +27,12 @@ func (m *mdnsWatcher) Next() (*registry.Result, error) {
 				continue
 			}
 
+			// Filter watch options
+			// wo.Service: Only keep services we care about
+			if len(m.wo.Service) > 0 && txt.Service != m.wo.Service {
+				continue
+			}
+
 			var action string
 
 			if e.TTL == 0 {

registry/mock/mock.go

@@ -87,8 +87,12 @@ func (m *mockRegistry) Deregister(s *registry.Service) error {
 	return nil
 }
 
-func (m *mockRegistry) Watch() (registry.Watcher, error) {
-	return &mockWatcher{exit: make(chan bool)}, nil
+func (m *mockRegistry) Watch(opts ...registry.WatchOption) (registry.Watcher, error) {
+	var wopts registry.WatchOptions
+	for _, o := range opts {
+		o(&wopts)
+	}
+	return &mockWatcher{exit: make(chan bool), opts: wopts}, nil
 }
 
 func (m *mockRegistry) String() string {

registry/mock/mock_watcher.go

@@ -8,6 +8,7 @@ import (
 
 type mockWatcher struct {
 	exit chan bool
+	opts registry.WatchOptions
 }
 
 func (m *mockWatcher) Next() (*registry.Result, error) {

registry/options.go

@@ -25,6 +25,15 @@ type RegisterOptions struct {
 	Context context.Context
 }
 
+type WatchOptions struct {
+	// Specify a service to watch
+	// If blank, the watch is for all services
+	Service string
+	// Other options for implementations of the interface
+	// can be stored in a context
+	Context context.Context
+}
+
 // Addrs is the registry addresses to use
 func Addrs(addrs ...string) Option {
 	return func(o *Options) {
@@ -57,3 +66,10 @@ func RegisterTTL(t time.Duration) RegisterOption {
 		o.TTL = t
 	}
 }
+
+// Watch a service
+func WatchService(name string) WatchOption {
+	return func(o *WatchOptions) {
+		o.Service = name
+	}
+}

registry/registry.go

@@ -13,7 +13,7 @@ type Registry interface {
 	Deregister(*Service) error
 	GetService(string) ([]*Service, error)
 	ListServices() ([]*Service, error)
-	Watch() (Watcher, error)
+	Watch(...WatchOption) (Watcher, error)
 	String() string
 }
 
@@ -21,6 +21,8 @@ type Option func(*Options)
 
 type RegisterOption func(*RegisterOptions)
 
+type WatchOption func(*WatchOptions)
+
 var (
 	DefaultRegistry = newConsulRegistry()
 
@@ -52,8 +54,8 @@ func ListServices() ([]*Service, error) {
 }
 
 // Watch returns a watcher which allows you to track updates to the registry.
-func Watch() (Watcher, error) {
-	return DefaultRegistry.Watch()
+func Watch(opts ...WatchOption) (Watcher, error) {
+	return DefaultRegistry.Watch(opts...)
 }
 
 func String() string {

selector/cache/cache.go

@@ -1,3 +1,4 @@
+// Package cache is a caching selector. It uses the registry watcher.
 package cache
 
 import (
@@ -9,11 +10,6 @@ import (
 	"github.com/micro/go-micro/selector"
 )
 
-/*
-	Cache selector is a selector which uses the registry.Watcher to Cache service entries.
-	It defaults to a TTL for 1 minute and causes a cache miss on the next request.
-*/
-
 type cacheSelector struct {
 	so  selector.Options
 	ttl time.Duration
@@ -23,7 +19,7 @@ type cacheSelector struct {
 	cache map[string][]*registry.Service
 	ttls  map[string]time.Time
 
-	once sync.Once
+	watched map[string]bool
 
 	// used to close or reload watcher
 	reload chan bool
@@ -88,6 +84,12 @@ func (c *cacheSelector) get(service string) ([]*registry.Service, error) {
 	c.Lock()
 	defer c.Unlock()
 
+	// watch service if not watched
+	if _, ok := c.watched[service]; !ok {
+		go c.run(service)
+		c.watched[service] = true
+	}
+
 	// get does the actual request for a service
 	// it also caches it
 	get := func(service string) ([]*registry.Service, error) {
@@ -254,7 +256,7 @@ func (c *cacheSelector) update(res *registry.Result) {
 // it creates a new watcher if there's a problem
 // reloads the watcher if Init is called
 // and returns when Close is called
-func (c *cacheSelector) run() {
+func (c *cacheSelector) run(name string) {
 	for {
 		// exit early if already dead
 		if c.quit() {
@@ -262,7 +264,9 @@ func (c *cacheSelector) run() {
 		}
 
 		// create new watcher
-		w, err := c.so.Registry.Watch()
+		w, err := c.so.Registry.Watch(
+			registry.WatchService(name),
+		)
 		if err != nil {
 			if c.quit() {
 				return
@@ -332,10 +336,6 @@ func (c *cacheSelector) Options() selector.Options {
 }
 
 func (c *cacheSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) {
-	c.once.Do(func() {
-		go c.run()
-	})
-
 	sopts := selector.SelectOptions{
 		Strategy: c.so.Strategy,
 	}
@@ -377,6 +377,7 @@ func (c *cacheSelector) Reset(service string) {
 func (c *cacheSelector) Close() error {
 	c.Lock()
 	c.cache = make(map[string][]*registry.Service)
+	c.watched = make(map[string]bool)
 	c.Unlock()
 
 	select {
@@ -416,6 +417,7 @@ func NewSelector(opts ...selector.Option) selector.Selector {
 	return &cacheSelector{
 		so:      sopts,
 		ttl:     ttl,
+		watched: make(map[string]bool),
 		cache:   make(map[string][]*registry.Service),
 		ttls:    make(map[string]time.Time),
 		reload:  make(chan bool, 1),