Merge pull request #78 from micro/cache

Caching Selector

cmd/cmd.go

@@ -24,6 +24,7 @@ import (
 	// selectors
 	"github.com/micro/go-micro/selector"
 	"github.com/micro/go-micro/selector/blacklist"
+	"github.com/micro/go-micro/selector/cache"
 	"github.com/micro/go-micro/selector/random"
 	"github.com/micro/go-micro/selector/roundrobin"
 
@@ -141,6 +142,7 @@ var (
 	}
 
 	DefaultSelectors = map[string]func(...selector.Option) selector.Selector{
+		"cache":      cache.NewSelector,
 		"random":     random.NewSelector,
 		"roundrobin": roundrobin.NewSelector,
 		"blacklist":  blacklist.NewSelector,

selector/cache/cache.go

@@ -0,0 +1,370 @@
+package cache
+
+import (
+	"log"
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
+)
+
+type cacheSelector struct {
+	so selector.Options
+
+	// registry cache
+	sync.Mutex
+	cache map[string][]*registry.Service
+
+	// used to close or reload watcher
+	reload chan bool
+	exit   chan bool
+}
+
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
+func (c *cacheSelector) quit() bool {
+	select {
+	case <-c.exit:
+		return true
+	default:
+		return false
+	}
+}
+
+// cp copies a service. Because we're caching handing back pointers would
+// create a race condition, so we do this instead
+// its fast enough
+func (c *cacheSelector) cp(current []*registry.Service) []*registry.Service {
+	var services []*registry.Service
+
+	for _, service := range current {
+		// copy service
+		s := new(registry.Service)
+		*s = *service
+
+		// copy nodes
+		var nodes []*registry.Node
+		for _, node := range service.Nodes {
+			n := new(registry.Node)
+			*n = *node
+			nodes = append(nodes, n)
+		}
+		s.Nodes = nodes
+
+		// copy endpoints
+		var eps []*registry.Endpoint
+		for _, ep := range service.Endpoints {
+			e := new(registry.Endpoint)
+			*e = *ep
+			eps = append(eps, e)
+		}
+		s.Endpoints = eps
+
+		// append service
+		services = append(services, s)
+	}
+
+	return services
+}
+
+func (c *cacheSelector) get(service string) ([]*registry.Service, error) {
+	c.Lock()
+	defer c.Unlock()
+
+	// check the cache first
+	services, ok := c.cache[service]
+
+	// got results, copy and return
+	if ok && len(services) > 0 {
+		return c.cp(services), nil
+	}
+
+	// now ask the registry
+	services, err := c.so.Registry.GetService(service)
+	if err != nil {
+		return nil, err
+
+	}
+
+	// we didn't have any results so cache
+	c.cache[service] = services
+
+	return services, nil
+}
+
+func (c *cacheSelector) update(res *registry.Result) {
+	if res == nil || res.Service == nil {
+		return
+	}
+
+	c.Lock()
+	defer c.Unlock()
+
+	services, ok := c.cache[res.Service.Name]
+	if !ok {
+		// we're not going to cache anything
+		// unless there was already a lookup
+		return
+	}
+
+	if len(res.Service.Nodes) == 0 {
+		switch res.Action {
+		case "delete":
+			delete(c.cache, res.Service.Name)
+		}
+		return
+	}
+
+	// existing service found
+	var service *registry.Service
+	var index int
+	for i, s := range services {
+		if s.Version == res.Service.Version {
+			service = s
+			index = i
+		}
+	}
+
+	switch res.Action {
+	case "create", "update":
+		if service == nil {
+			services = append(services, res.Service)
+			c.cache[res.Service.Name] = services
+			return
+		}
+
+		// append old nodes to new service
+		for _, cur := range service.Nodes {
+			var seen bool
+			for _, node := range res.Service.Nodes {
+				if cur.Id == node.Id {
+					seen = true
+					break
+				}
+			}
+			if !seen {
+				res.Service.Nodes = append(res.Service.Nodes, cur)
+			}
+		}
+
+		services[index] = res.Service
+		c.cache[res.Service.Name] = services
+	case "delete":
+		if service == nil {
+			return
+		}
+
+		var nodes []*registry.Node
+
+		// filter cur nodes to remove the dead one
+		for _, cur := range service.Nodes {
+			var seen bool
+			for _, del := range res.Service.Nodes {
+				if del.Id == cur.Id {
+					seen = true
+					break
+				}
+			}
+			if !seen {
+				nodes = append(nodes, cur)
+			}
+		}
+
+		if len(nodes) == 0 {
+			if len(services) == 1 {
+				delete(c.cache, service.Name)
+			} else {
+				var srvs []*registry.Service
+				for _, s := range services {
+					if s.Version != service.Version {
+						srvs = append(srvs, s)
+					}
+				}
+				c.cache[service.Name] = srvs
+			}
+			return
+		}
+
+		service.Nodes = nodes
+		services[index] = service
+		c.cache[res.Service.Name] = services
+	}
+}
+
+// run starts the cache watcher loop
+// 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() {
+	for {
+		// exit early if already dead
+		if c.quit() {
+			return
+		}
+
+		// create new watcher
+		w, err := c.so.Registry.Watch()
+		if err != nil {
+			log.Println(err)
+			time.Sleep(time.Second)
+			continue
+		}
+
+		// manage this loop
+		go func() {
+			// wait for exit or reload signal
+			select {
+			case <-c.exit:
+			case <-c.reload:
+			}
+
+			// stop the watcher
+			w.Stop()
+		}()
+
+		// watch for events
+		if err := c.watch(w); err != nil {
+			log.Println(err)
+			continue
+		}
+	}
+}
+
+// watch loops the next event and calls update
+// it returns if there's an error
+func (c *cacheSelector) watch(w registry.Watcher) error {
+	for {
+		res, err := w.Next()
+		if err != nil {
+			return err
+		}
+		c.update(res)
+	}
+}
+
+func (c *cacheSelector) Init(opts ...selector.Option) error {
+	for _, o := range opts {
+		o(&c.so)
+	}
+
+	// reload the watcher
+	go func() {
+		select {
+		case <-c.exit:
+			return
+		default:
+			c.reload <- true
+		}
+	}()
+
+	return nil
+}
+
+func (c *cacheSelector) Options() selector.Options {
+	return c.so
+}
+
+func (c *cacheSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) {
+	var sopts selector.SelectOptions
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	// get the service
+	// try the cache first
+	// if that fails go directly to the registry
+	services, err := c.get(service)
+	if err != nil {
+		return nil, err
+	}
+
+	// apply the filters
+	for _, filter := range sopts.Filters {
+		services = filter(services)
+	}
+
+	// if there's nothing left, return
+	if len(services) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	var nodes []*registry.Node
+
+	for _, service := range services {
+		for _, node := range service.Nodes {
+			nodes = append(nodes, node)
+		}
+	}
+
+	if len(nodes) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	return func() (*registry.Node, error) {
+		i := rand.Int()
+		j := i % len(services)
+
+		if len(services[j].Nodes) == 0 {
+			return nil, selector.ErrNotFound
+		}
+
+		k := i % len(services[j].Nodes)
+		return services[j].Nodes[k], nil
+	}, nil
+}
+
+func (c *cacheSelector) Mark(service string, node *registry.Node, err error) {
+	return
+}
+
+func (c *cacheSelector) Reset(service string) {
+	c.Lock()
+	delete(c.cache, service)
+	c.Unlock()
+}
+
+// Close stops the watcher and destroys the cache
+func (c *cacheSelector) Close() error {
+	c.Lock()
+	c.cache = make(map[string][]*registry.Service)
+	c.Unlock()
+
+	select {
+	case <-c.exit:
+		return nil
+	default:
+		close(c.exit)
+	}
+	return nil
+}
+
+func (c *cacheSelector) String() string {
+	return "cache"
+}
+
+func NewSelector(opts ...selector.Option) selector.Selector {
+	var sopts selector.Options
+
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	if sopts.Registry == nil {
+		sopts.Registry = registry.DefaultRegistry
+	}
+
+	c := &cacheSelector{
+		so:     sopts,
+		cache:  make(map[string][]*registry.Service),
+		reload: make(chan bool, 1),
+		exit:   make(chan bool),
+	}
+
+	go c.run()
+
+	return c
+}

selector/cache/cache_test.go

@@ -0,0 +1,29 @@
+package cache
+
+import (
+	"testing"
+
+	"github.com/micro/go-micro/registry/mock"
+	"github.com/micro/go-micro/selector"
+)
+
+func TestCacheSelector(t *testing.T) {
+	counts := map[string]int{}
+
+	cache := NewSelector(selector.Registry(mock.NewRegistry()))
+
+	next, err := cache.Select("foo")
+	if err != nil {
+		t.Errorf("Unexpected error calling cache select: %v", err)
+	}
+
+	for i := 0; i < 100; i++ {
+		node, err := next()
+		if err != nil {
+			t.Errorf("Expected node err, got err: %v", err)
+		}
+		counts[node.Id]++
+	}
+
+	t.Logf("Cache Counts %v", counts)
+}