Merge pull request #25 from micro/selector

Add selector interface and implementation

README.md

@@ -16,6 +16,7 @@ Feature		| Package	|	Built-in Plugin		|	Description
 Discovery	| [Registry](https://godoc.org/github.com/micro/go-micro/registry)	| consul	| A way of locating services to communicate with
 Client		| [Client](https://godoc.org/github.com/micro/go-micro/client)	| rpc	| Used to make RPC requests to a service
 Codec		| [Codec](https://godoc.org/github.com/micro/go-micro/codec)	| proto,json	| Encoding/Decoding handler for requests
+Selector	| [Selector](https://godoc.org/github.com/micro/go-micro/selector)	| random	| Service node filter and pool 
 Server		| [Server](https://godoc.org/github.com/micro/go-micro/server)	| rpc	| Listens and serves RPC requests
 Pub/Sub		| [Broker](https://godoc.org/github.com/micro/go-micro/broker)	| http	| Publish and Subscribe to events
 Transport	| [Transport](https://godoc.org/github.com/micro/go-micro/transport)	| http	| Communication mechanism between services

client/client_selector.go

@@ -1,9 +0,0 @@
-package client
-
-import (
-	"github.com/micro/go-micro/registry"
-)
-
-// Selector takes a Registry and returns a NodeSelector.
-// Used by the client to initialise a selector.
-type Selector func(registry.Registry) NodeSelector

client/node_selector.go

@@ -1,60 +0,0 @@
-package client
-
-import (
-	"math/rand"
-	"time"
-
-	"github.com/micro/go-micro/errors"
-	"github.com/micro/go-micro/registry"
-	"golang.org/x/net/context"
-)
-
-// NodeSelector is used to Retrieve a node to which a request
-// should be routed. It takes context and Request and returns a
-// single node. If a node cannot be selected it should return
-// an error. Response is called to inform the selector of the
-// response from a client call. Reset is called to zero out
-// any state.
-type NodeSelector interface {
-	Select(context.Context, Request) (*registry.Node, error)
-	Response(*registry.Node, error)
-	Reset()
-}
-
-func init() {
-	rand.Seed(time.Now().UnixNano())
-}
-
-// Built in random hashed node selector
-type nodeSelector struct {
-	r registry.Registry
-}
-
-func (n *nodeSelector) Select(ctx context.Context, req Request) (*registry.Node, error) {
-	service, err := n.r.GetService(req.Service())
-	if err != nil {
-		return nil, errors.InternalServerError("go.micro.client", err.Error())
-	}
-
-	if len(service) == 0 {
-		return nil, errors.NotFound("go.micro.client", "Service not found")
-	}
-
-	i := rand.Int()
-	j := i % len(service)
-
-	if len(service[j].Nodes) == 0 {
-		return nil, errors.NotFound("go.micro.client", "Service not found")
-	}
-
-	k := i % len(service[j].Nodes)
-	return service[j].Nodes[k], nil
-}
-
-func (n *nodeSelector) Response(node *registry.Node, err error) {
-	return
-}
-
-func (n *nodeSelector) Reset() {
-	return
-}

client/node_selector_test.go

@@ -1,70 +0,0 @@
-package client
-
-import (
-	"testing"
-
-	"github.com/micro/go-micro/registry"
-	"golang.org/x/net/context"
-)
-
-type mockRegistry struct{}
-
-func (m *mockRegistry) GetService(service string) ([]*registry.Service, error) {
-	return []*registry.Service{
-		{
-			Name:    "foo",
-			Version: "1.0.0",
-			Nodes: []*registry.Node{
-				{
-					Id:      "foo-123",
-					Address: "localhost",
-					Port:    9999,
-				},
-			},
-		},
-		{
-			Name:    "foo",
-			Version: "1.0.1",
-			Nodes: []*registry.Node{
-				{
-					Id:      "foo-321",
-					Address: "localhost",
-					Port:    6666,
-				},
-			},
-		},
-	}, nil
-}
-
-func (m *mockRegistry) ListServices() ([]*registry.Service, error) {
-	return []*registry.Service{}, nil
-}
-
-func (m *mockRegistry) Register(s *registry.Service) error {
-	return nil
-}
-
-func (m *mockRegistry) Deregister(s *registry.Service) error {
-	return nil
-}
-
-func (m *mockRegistry) Watch() (registry.Watcher, error) {
-	return nil, nil
-}
-
-func TestNodeSelector(t *testing.T) {
-	counts := map[string]int{}
-	n := &nodeSelector{
-		&mockRegistry{},
-	}
-
-	for i := 0; i < 100; i++ {
-		n, err := n.Select(context.Background(), newRpcRequest("foo", "Foo.Bar", nil, ""))
-		if err != nil {
-			t.Errorf("Expected node, got err: %v", err)
-		}
-		counts[n.Id]++
-	}
-
-	t.Logf("Counts %v", counts)
-}

client/options.go

@@ -4,6 +4,7 @@ import (
 	"github.com/micro/go-micro/broker"
 	"github.com/micro/go-micro/codec"
 	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
 	"github.com/micro/go-micro/transport"
 )
 
@@ -12,12 +13,14 @@ type options struct {
 	broker      broker.Broker
 	codecs      map[string]codec.NewCodec
 	registry    registry.Registry
+	selector    selector.Selector
 	transport   transport.Transport
 	wrappers    []Wrapper
-	selector    Selector
 }
 
-type callOptions struct{}
+type callOptions struct {
+	selectOptions []selector.SelectOption
+}
 
 type publishOptions struct{}
 
@@ -57,7 +60,7 @@ func Transport(t transport.Transport) Option {
 }
 
 // Select is used to select a node to route a request to
-func Select(s Selector) Option {
+func Selector(s selector.Selector) Option {
 	return func(o *options) {
 		o.selector = s
 	}
@@ -69,3 +72,11 @@ func Wrap(w Wrapper) Option {
 		o.wrappers = append(o.wrappers, w)
 	}
 }
+
+// Call Options
+
+func WithSelectOption(so selector.SelectOption) CallOption {
+	return func(o *callOptions) {
+		o.selectOptions = append(o.selectOptions, so)
+	}
+}

client/rpc_client.go

@@ -10,6 +10,7 @@ import (
 	c "github.com/micro/go-micro/context"
 	"github.com/micro/go-micro/errors"
 	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
 	"github.com/micro/go-micro/transport"
 
 	"golang.org/x/net/context"
@@ -18,11 +19,9 @@ import (
 type rpcClient struct {
 	once sync.Once
 	opts options
-	sel  NodeSelector
 }
 
 func newRpcClient(opt ...Option) Client {
-	var sel NodeSelector
 	var once sync.Once
 
 	opts := options{
@@ -37,28 +36,27 @@ func newRpcClient(opt ...Option) Client {
 		opts.contentType = defaultContentType
 	}
 
-	if opts.transport == nil {
-		opts.transport = transport.DefaultTransport
+	if opts.broker == nil {
+		opts.broker = broker.DefaultBroker
 	}
 
 	if opts.registry == nil {
 		opts.registry = registry.DefaultRegistry
 	}
 
-	if opts.broker == nil {
-		opts.broker = broker.DefaultBroker
+	if opts.selector == nil {
+		opts.selector = selector.NewSelector(
+			selector.Registry(opts.registry),
+		)
 	}
 
-	if opts.selector != nil {
-		sel = opts.selector(opts.registry)
-	} else {
-		sel = &nodeSelector{opts.registry}
+	if opts.transport == nil {
+		opts.transport = transport.DefaultTransport
 	}
 
 	rc := &rpcClient{
 		once: once,
 		opts: opts,
-		sel:  sel,
 	}
 
 	c := Client(rc)
@@ -153,9 +151,23 @@ func (r *rpcClient) CallRemote(ctx context.Context, address string, request Requ
 }
 
 func (r *rpcClient) Call(ctx context.Context, request Request, response interface{}, opts ...CallOption) error {
-	node, err := r.sel.Select(ctx, request)
-	if err != nil {
-		return err
+	var copts callOptions
+	for _, opt := range opts {
+		opt(&copts)
+	}
+
+	next, err := r.opts.selector.Select(request.Service(), copts.selectOptions...)
+	if err != nil && err == selector.ErrNotFound {
+		return errors.NotFound("go.micro.client", err.Error())
+	} else if err != nil {
+		return errors.InternalServerError("go.micro.client", err.Error())
+	}
+
+	node, err := next()
+	if err != nil && err == selector.ErrNotFound {
+		return errors.NotFound("go.micro.client", err.Error())
+	} else if err != nil {
+		return errors.InternalServerError("go.micro.client", err.Error())
 	}
 
 	address := node.Address
@@ -164,7 +176,7 @@ func (r *rpcClient) Call(ctx context.Context, request Request, response interfac
 	}
 
 	err = r.call(ctx, address, request, response)
-	r.sel.Response(node, err)
+	r.opts.selector.Mark(request.Service(), node, err)
 	return err
 }
 
@@ -173,9 +185,23 @@ func (r *rpcClient) StreamRemote(ctx context.Context, address string, request Re
 }
 
 func (r *rpcClient) Stream(ctx context.Context, request Request, responseChan interface{}, opts ...CallOption) (Streamer, error) {
-	node, err := r.sel.Select(ctx, request)
-	if err != nil {
-		return nil, err
+	var copts callOptions
+	for _, opt := range opts {
+		opt(&copts)
+	}
+
+	next, err := r.opts.selector.Select(request.Service(), copts.selectOptions...)
+	if err != nil && err == selector.ErrNotFound {
+		return nil, errors.NotFound("go.micro.client", err.Error())
+	} else if err != nil {
+		return nil, errors.InternalServerError("go.micro.client", err.Error())
+	}
+
+	node, err := next()
+	if err != nil && err == selector.ErrNotFound {
+		return nil, errors.NotFound("go.micro.client", err.Error())
+	} else if err != nil {
+		return nil, errors.InternalServerError("go.micro.client", err.Error())
 	}
 
 	address := node.Address
@@ -184,7 +210,7 @@ func (r *rpcClient) Stream(ctx context.Context, request Request, responseChan in
 	}
 
 	stream, err := r.stream(ctx, address, request, responseChan)
-	r.sel.Response(node, err)
+	r.opts.selector.Mark(request.Service(), node, err)
 	return stream, err
 }
 

cmd/cmd.go

@@ -19,6 +19,7 @@ import (
 	"github.com/micro/go-micro/broker"
 	"github.com/micro/go-micro/client"
 	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
 	"github.com/micro/go-micro/server"
 	"github.com/micro/go-micro/transport"
 	"github.com/pborman/uuid"
@@ -80,6 +81,12 @@ var (
 			EnvVar: "MICRO_REGISTRY_ADDRESS",
 			Usage:  "Comma-separated list of registry addresses",
 		},
+		cli.StringFlag{
+			Name:   "selector",
+			EnvVar: "MICRO_SELECTOR",
+			Value:  "selector",
+			Usage:  "Selector used to pick nodes for querying. random, roundrobin, blacklist",
+		},
 		cli.StringFlag{
 			Name:   "transport",
 			EnvVar: "MICRO_TRANSPORT",
@@ -137,6 +144,10 @@ var (
 		"consul": registry.NewRegistry,
 	}
 
+	Selectors = map[string]func(...selector.Option) selector.Selector{
+		"random": selector.NewSelector,
+	}
+
 	Transports = map[string]func([]string, ...transport.Option) transport.Transport{
 		"http": transport.NewTransport,
 	}
@@ -214,6 +225,10 @@ func Setup(c *cli.Context) error {
 		registry.DefaultRegistry = r(strings.Split(c.String("registry_address"), ","))
 	}
 
+	if s, ok := Selectors[c.String("selector")]; ok {
+		selector.DefaultSelector = s(selector.Registry(registry.DefaultRegistry))
+	}
+
 	if t, ok := Transports[c.String("transport")]; ok {
 		transport.DefaultTransport = t(strings.Split(c.String("transport_address"), ","))
 	}

examples/client/dc_filter/dc_filter.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"time"
+
+	"github.com/micro/go-micro/client"
+	"github.com/micro/go-micro/cmd"
+	c "github.com/micro/go-micro/context"
+	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
+	"golang.org/x/net/context"
+
+	example "github.com/micro/go-micro/examples/server/proto/example"
+)
+
+func init() {
+	rand.Seed(time.Now().Unix())
+}
+
+// A Wrapper that creates a Datacenter Selector Option
+type dcWrapper struct {
+	client.Client
+}
+
+func (dc *dcWrapper) Call(ctx context.Context, req client.Request, rsp interface{}, opts ...client.CallOption) error {
+	md, _ := c.GetMetadata(ctx)
+
+	filter := func(services []*registry.Service) []*registry.Service {
+		for _, service := range services {
+			var nodes []*registry.Node
+			for _, node := range service.Nodes {
+				if node.Metadata["datacenter"] == md["datacenter"] {
+					nodes = append(nodes, node)
+				}
+			}
+			service.Nodes = nodes
+		}
+		return services
+	}
+
+	callOptions := append(opts, client.WithSelectOption(
+		selector.Filter(filter),
+	))
+
+	fmt.Printf("[DC Wrapper] filtering for datacenter %s\n", md["datacenter"])
+	return dc.Client.Call(ctx, req, rsp, callOptions...)
+}
+
+func NewDCWrapper(c client.Client) client.Client {
+	return &dcWrapper{c}
+}
+
+func call(i int) {
+	// Create new request to service go.micro.srv.example, method Example.Call
+	req := client.NewRequest("go.micro.srv.example", "Example.Call", &example.Request{
+		Name: "John",
+	})
+
+	// create context with metadata
+	ctx := c.WithMetadata(context.Background(), map[string]string{
+		"datacenter": "local",
+	})
+
+	rsp := &example.Response{}
+
+	// Call service
+	if err := client.Call(ctx, req, rsp); err != nil {
+		fmt.Println("call err: ", err, rsp)
+		return
+	}
+
+	fmt.Println("Call:", i, "rsp:", rsp.Msg)
+}
+
+func main() {
+	cmd.Init()
+
+	client.DefaultClient = client.NewClient(
+		client.Wrap(NewDCWrapper),
+	)
+
+	fmt.Println("\n--- Call example ---\n")
+	for i := 0; i < 10; i++ {
+		call(i)
+	}
+}

examples/client/dc_selector/dc_selector.go

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/micro/go-micro/client"
+	"github.com/micro/go-micro/cmd"
+	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
+	"golang.org/x/net/context"
+
+	example "github.com/micro/go-micro/examples/server/proto/example"
+)
+
+// Built in random hashed node selector
+type dcSelector struct {
+	opts selector.Options
+}
+
+var (
+	datacenter = "local"
+)
+
+func init() {
+	rand.Seed(time.Now().Unix())
+}
+
+func (n *dcSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) {
+	services, err := n.opts.Registry.GetService(service)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(services) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	var nodes []*registry.Node
+
+	// Filter the nodes for datacenter
+	for _, service := range services {
+		for _, node := range service.Nodes {
+			if node.Metadata["datacenter"] == datacenter {
+				nodes = append(nodes, node)
+			}
+		}
+	}
+
+	if len(nodes) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	var i int
+	var mtx sync.Mutex
+
+	return func() (*registry.Node, error) {
+		mtx.Lock()
+		defer mtx.Unlock()
+		i++
+		return nodes[i%len(nodes)], nil
+	}, nil
+}
+
+func (n *dcSelector) Mark(service string, node *registry.Node, err error) {
+	return
+}
+
+func (n *dcSelector) Reset(service string) {
+	return
+}
+
+func (n *dcSelector) Close() error {
+	return nil
+}
+
+// Return a new first node selector
+func DCSelector(opts ...selector.Option) selector.Selector {
+	var sopts selector.Options
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+	if sopts.Registry == nil {
+		sopts.Registry = registry.DefaultRegistry
+	}
+	return &dcSelector{sopts}
+}
+
+func call(i int) {
+	// Create new request to service go.micro.srv.example, method Example.Call
+	req := client.NewRequest("go.micro.srv.example", "Example.Call", &example.Request{
+		Name: "John",
+	})
+
+	rsp := &example.Response{}
+
+	// Call service
+	if err := client.Call(context.Background(), req, rsp); err != nil {
+		fmt.Println("call err: ", err, rsp)
+		return
+	}
+
+	fmt.Println("Call:", i, "rsp:", rsp.Msg)
+}
+
+func main() {
+	cmd.Init()
+
+	client.DefaultClient = client.NewClient(
+		client.Selector(DCSelector()),
+	)
+
+	fmt.Println("\n--- Call example ---\n")
+	for i := 0; i < 10; i++ {
+		call(i)
+	}
+}

examples/client/node_selector/node_selector.go

@@ -1,87 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"math/rand"
-	"time"
-
-	"github.com/micro/go-micro/client"
-	"github.com/micro/go-micro/cmd"
-	"github.com/micro/go-micro/errors"
-	example "github.com/micro/go-micro/examples/server/proto/example"
-	"github.com/micro/go-micro/registry"
-	"golang.org/x/net/context"
-)
-
-func init() {
-	rand.Seed(time.Now().Unix())
-}
-
-// Built in random hashed node selector
-type nodeSelector struct {
-	r registry.Registry
-}
-
-func (n *nodeSelector) Select(ctx context.Context, req client.Request) (*registry.Node, error) {
-	service, err := n.r.GetService(req.Service())
-	if err != nil {
-		return nil, errors.InternalServerError("go.micro.client", err.Error())
-	}
-
-	if len(service) == 0 {
-		return nil, errors.NotFound("go.micro.client", "Service not found")
-	}
-
-	i := rand.Int()
-	j := i % len(service)
-
-	if len(service[j].Nodes) == 0 {
-		return nil, errors.NotFound("go.micro.client", "Service not found")
-	}
-
-	k := i % len(service[j].Nodes)
-	return service[j].Nodes[k], nil
-}
-
-func (n *nodeSelector) Response(node *registry.Node, err error) {
-	return
-}
-
-func (n *nodeSelector) Reset() {
-	return
-}
-
-// Return a new random node selector
-func RandomSelector(r registry.Registry) client.NodeSelector {
-	return &nodeSelector{r}
-}
-
-func call(i int) {
-	// Create new request to service go.micro.srv.example, method Example.Call
-	req := client.NewRequest("go.micro.srv.example", "Example.Call", &example.Request{
-		Name: "John",
-	})
-
-	rsp := &example.Response{}
-
-	// Call service
-	if err := client.Call(context.Background(), req, rsp); err != nil {
-		fmt.Println("call err: ", err, rsp)
-		return
-	}
-
-	fmt.Println("Call:", i, "rsp:", rsp.Msg)
-}
-
-func main() {
-	cmd.Init()
-
-	client.DefaultClient = client.NewClient(
-		client.Select(RandomSelector),
-	)
-
-	fmt.Println("\n--- Call example ---\n")
-	for i := 0; i < 10; i++ {
-		call(i)
-	}
-}

examples/client/selector/selector.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"time"
+
+	"github.com/micro/go-micro/client"
+	"github.com/micro/go-micro/cmd"
+	example "github.com/micro/go-micro/examples/server/proto/example"
+	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
+	"golang.org/x/net/context"
+)
+
+func init() {
+	rand.Seed(time.Now().Unix())
+}
+
+// Built in random hashed node selector
+type firstNodeSelector struct {
+	opts selector.Options
+}
+
+func (n *firstNodeSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) {
+	services, err := n.opts.Registry.GetService(service)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(services) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	var sopts selector.SelectOptions
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	for _, filter := range sopts.Filters {
+		services = filter(services)
+	}
+
+	if len(services) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	if len(services[0].Nodes) == 0 {
+		return nil, selector.ErrNotFound
+	}
+
+	return func() (*registry.Node, error) {
+		return services[0].Nodes[0], nil
+	}, nil
+}
+
+func (n *firstNodeSelector) Mark(service string, node *registry.Node, err error) {
+	return
+}
+
+func (n *firstNodeSelector) Reset(service string) {
+	return
+}
+
+func (n *firstNodeSelector) Close() error {
+	return nil
+}
+
+// Return a new first node selector
+func FirstNodeSelector(opts ...selector.Option) selector.Selector {
+	var sopts selector.Options
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+	if sopts.Registry == nil {
+		sopts.Registry = registry.DefaultRegistry
+	}
+	return &firstNodeSelector{sopts}
+}
+
+func call(i int) {
+	// Create new request to service go.micro.srv.example, method Example.Call
+	req := client.NewRequest("go.micro.srv.example", "Example.Call", &example.Request{
+		Name: "John",
+	})
+
+	rsp := &example.Response{}
+
+	// Call service
+	if err := client.Call(context.Background(), req, rsp); err != nil {
+		fmt.Println("call err: ", err, rsp)
+		return
+	}
+
+	fmt.Println("Call:", i, "rsp:", rsp.Msg)
+}
+
+func main() {
+	cmd.Init()
+
+	client.DefaultClient = client.NewClient(
+		client.Selector(FirstNodeSelector()),
+	)
+
+	fmt.Println("\n--- Call example ---\n")
+	for i := 0; i < 10; i++ {
+		call(i)
+	}
+}

examples/server/main.go

@@ -31,9 +31,13 @@ func main() {
 	// optionally setup command line usage
 	cmd.Init()
 
+	md := server.Config().Metadata()
+	md["datacenter"] = "local"
+
 	server.DefaultServer = server.NewServer(
 		server.WrapHandler(logWrapper),
 		server.WrapSubscriber(logSubWrapper),
+		server.Metadata(md),
 	)
 
 	// Initialise Server

registry/mock/mock.go

@@ -0,0 +1,70 @@
+package mock
+
+import (
+	"github.com/micro/go-micro/registry"
+)
+
+type MockRegistry struct{}
+
+func (m *MockRegistry) GetService(service string) ([]*registry.Service, error) {
+	return []*registry.Service{
+		{
+			Name:    "foo",
+			Version: "1.0.0",
+			Nodes: []*registry.Node{
+				{
+					Id:      "foo-1.0.0-123",
+					Address: "localhost",
+					Port:    9999,
+				},
+				{
+					Id:      "foo-1.0.0-321",
+					Address: "localhost",
+					Port:    9999,
+				},
+			},
+		},
+		{
+			Name:    "foo",
+			Version: "1.0.1",
+			Nodes: []*registry.Node{
+				{
+					Id:      "foo-1.0.1-321",
+					Address: "localhost",
+					Port:    6666,
+				},
+			},
+		},
+		{
+			Name:    "foo",
+			Version: "1.0.3",
+			Nodes: []*registry.Node{
+				{
+					Id:      "foo-1.0.3-345",
+					Address: "localhost",
+					Port:    8888,
+				},
+			},
+		},
+	}, nil
+}
+
+func (m *MockRegistry) ListServices() ([]*registry.Service, error) {
+	return []*registry.Service{}, nil
+}
+
+func (m *MockRegistry) Register(s *registry.Service) error {
+	return nil
+}
+
+func (m *MockRegistry) Deregister(s *registry.Service) error {
+	return nil
+}
+
+func (m *MockRegistry) Watch() (registry.Watcher, error) {
+	return nil, nil
+}
+
+func NewRegistry() *MockRegistry {
+	return &MockRegistry{}
+}

selector/blacklist/black_list_selector.go

@@ -0,0 +1,169 @@
+package blacklist
+
+import (
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/micro/go-micro/cmd"
+	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
+)
+
+type blackListNode struct {
+	age     time.Time
+	id      string
+	service string
+}
+
+type blackListSelector struct {
+	so   selector.Options
+	ttl  int64
+	exit chan bool
+	once sync.Once
+
+	sync.RWMutex
+	bl map[string]blackListNode
+}
+
+func init() {
+	cmd.Selectors["blacklist"] = NewSelector
+	rand.Seed(time.Now().Unix())
+}
+
+func (r *blackListSelector) purge() {
+	now := time.Now()
+	r.Lock()
+	for k, v := range r.bl {
+		if d := v.age.Sub(now); d.Seconds() < 0 {
+			delete(r.bl, k)
+		}
+	}
+	r.Unlock()
+}
+
+func (r *blackListSelector) run() {
+	t := time.NewTicker(time.Duration(r.ttl) * time.Second)
+
+	for {
+		select {
+		case <-r.exit:
+			t.Stop()
+			return
+		case <-t.C:
+			r.purge()
+		}
+	}
+}
+
+func (r *blackListSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) {
+	var sopts selector.SelectOptions
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	// get the service
+	services, err := r.so.Registry.GetService(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) {
+		var viable []*registry.Node
+
+		r.RLock()
+		for _, node := range nodes {
+			if _, ok := r.bl[node.Id]; !ok {
+				viable = append(viable, node)
+			}
+		}
+		r.RUnlock()
+
+		if len(viable) == 0 {
+			return nil, selector.ErrNoneAvailable
+		}
+
+		return viable[rand.Int()%len(viable)], nil
+	}, nil
+}
+
+func (r *blackListSelector) Mark(service string, node *registry.Node, err error) {
+	r.Lock()
+	defer r.Unlock()
+	if err == nil {
+		delete(r.bl, node.Id)
+		return
+	}
+
+	r.bl[node.Id] = blackListNode{
+		age:     time.Now().Add(time.Duration(r.ttl) * time.Second),
+		id:      node.Id,
+		service: service,
+	}
+	return
+}
+
+func (r *blackListSelector) Reset(service string) {
+	r.Lock()
+	defer r.Unlock()
+	for k, v := range r.bl {
+		if v.service == service {
+			delete(r.bl, k)
+		}
+	}
+	return
+}
+
+func (r *blackListSelector) Close() error {
+	r.once.Do(func() {
+		close(r.exit)
+	})
+	return nil
+}
+
+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
+	}
+
+	var once sync.Once
+	bl := &blackListSelector{
+		once: once,
+		so:   sopts,
+		ttl:  60,
+		bl:   make(map[string]blackListNode),
+		exit: make(chan bool),
+	}
+
+	go bl.run()
+
+	return bl
+}

selector/blacklist/black_list_selector_test.go

@@ -0,0 +1,73 @@
+package blacklist
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/micro/go-micro/registry/mock"
+	"github.com/micro/go-micro/selector"
+)
+
+func TestBlackListSelector(t *testing.T) {
+	counts := map[string]int{}
+
+	bl := &blackListSelector{
+		so: selector.Options{
+			Registry: mock.NewRegistry(),
+		},
+		ttl:  2,
+		bl:   make(map[string]blackListNode),
+		exit: make(chan bool),
+	}
+
+	go bl.run()
+	defer bl.Close()
+
+	next, err := bl.Select("foo")
+	if err != nil {
+		t.Errorf("Unexpected error calling bl 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("BlackList Counts %v", counts)
+
+	// test blacklisting
+	for i := 0; i < 4; i++ {
+		node, err := next()
+		if err != nil {
+			t.Errorf("Expected node err, got err: %v", err)
+		}
+		bl.Mark("foo", node, errors.New("blacklist"))
+	}
+	if node, err := next(); err != selector.ErrNoneAvailable {
+		t.Errorf("Expected none available err, got node %v err %v", node, err)
+	}
+	time.Sleep(time.Second * time.Duration(bl.ttl) * 2)
+	if _, err := next(); err != nil {
+		t.Errorf("Unexpected err %v", err)
+	}
+
+	// test resetting
+	for i := 0; i < 4; i++ {
+		node, err := next()
+		if err != nil {
+			t.Errorf("Unexpected err: %v", err)
+		}
+		bl.Mark("foo", node, errors.New("blacklist"))
+	}
+	if node, err := next(); err != selector.ErrNoneAvailable {
+		t.Errorf("Expected none available err, got node %v err %v", node, err)
+	}
+	bl.Reset("foo")
+	if _, err := next(); err != nil {
+		t.Errorf("Unexpected err %v", err)
+	}
+}

selector/options.go

@@ -0,0 +1,34 @@
+package selector
+
+import (
+	"github.com/micro/go-micro/registry"
+)
+
+type Options struct {
+	Registry registry.Registry
+}
+
+type SelectOptions struct {
+	Filters []SelectFilter
+}
+
+// Option used to initialise the selector
+type Option func(*Options)
+
+// SelectOption used when making a select call
+type SelectOption func(*SelectOptions)
+
+// Registry sets the registry used by the selector
+func Registry(r registry.Registry) Option {
+	return func(o *Options) {
+		o.Registry = r
+	}
+}
+
+// Filter adds a filter function to the list of filters
+// used during the Select call.
+func Filter(fn SelectFilter) SelectOption {
+	return func(o *SelectOptions) {
+		o.Filters = append(o.Filters, fn)
+	}
+}

selector/random/random.go

@@ -0,0 +1,14 @@
+package random
+
+import (
+	"github.com/micro/go-micro/cmd"
+	"github.com/micro/go-micro/selector"
+)
+
+func init() {
+	cmd.Selectors["random"] = NewSelector
+}
+
+func NewSelector(opts ...selector.Option) selector.Selector {
+	return selector.NewSelector(opts...)
+}

selector/random_selector.go

@@ -0,0 +1,89 @@
+package selector
+
+import (
+	"math/rand"
+	"time"
+
+	"github.com/micro/go-micro/registry"
+)
+
+type randomSelector struct {
+	so Options
+}
+
+func init() {
+	rand.Seed(time.Now().Unix())
+}
+
+func (r *randomSelector) Select(service string, opts ...SelectOption) (Next, error) {
+	var sopts SelectOptions
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	// get the service
+	services, err := r.so.Registry.GetService(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, ErrNotFound
+	}
+
+	var nodes []*registry.Node
+
+	for _, service := range services {
+		for _, node := range service.Nodes {
+			nodes = append(nodes, node)
+		}
+	}
+
+	if len(nodes) == 0 {
+		return nil, ErrNotFound
+	}
+
+	return func() (*registry.Node, error) {
+		i := rand.Int()
+		j := i % len(services)
+
+		if len(services[j].Nodes) == 0 {
+			return nil, ErrNotFound
+		}
+
+		k := i % len(services[j].Nodes)
+		return services[j].Nodes[k], nil
+	}, nil
+}
+
+func (r *randomSelector) Mark(service string, node *registry.Node, err error) {
+	return
+}
+
+func (r *randomSelector) Reset(service string) {
+	return
+}
+
+func (r *randomSelector) Close() error {
+	return nil
+}
+
+func newRandomSelector(opts ...Option) Selector {
+	var sopts Options
+
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	if sopts.Registry == nil {
+		sopts.Registry = registry.DefaultRegistry
+	}
+
+	return &randomSelector{sopts}
+}

selector/random_selector_test.go

@@ -0,0 +1,32 @@
+package selector
+
+import (
+	"testing"
+
+	"github.com/micro/go-micro/registry/mock"
+)
+
+func TestRandomSelector(t *testing.T) {
+	counts := map[string]int{}
+
+	bl := &randomSelector{
+		so: Options{
+			Registry: mock.NewRegistry(),
+		},
+	}
+
+	next, err := bl.Select("foo")
+	if err != nil {
+		t.Errorf("Unexpected error calling random 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("Random Counts %v", counts)
+}

selector/roundrobin/round_robin_selector.go

@@ -0,0 +1,88 @@
+package roundrobin
+
+import (
+	"sync"
+
+	"github.com/micro/go-micro/cmd"
+	"github.com/micro/go-micro/registry"
+	"github.com/micro/go-micro/selector"
+)
+
+type roundRobinSelector struct {
+	so selector.Options
+}
+
+func init() {
+	cmd.Selectors["roundrobin"] = NewSelector
+}
+
+func (r *roundRobinSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) {
+	var sopts selector.SelectOptions
+	for _, opt := range opts {
+		opt(&sopts)
+	}
+
+	// get the service
+	services, err := r.so.Registry.GetService(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
+	}
+
+	var i int
+	var mtx sync.Mutex
+
+	return func() (*registry.Node, error) {
+		mtx.Lock()
+		defer mtx.Unlock()
+		i++
+		return nodes[i%len(nodes)], nil
+	}, nil
+}
+
+func (r *roundRobinSelector) Mark(service string, node *registry.Node, err error) {
+	return
+}
+
+func (r *roundRobinSelector) Reset(service string) {
+	return
+}
+
+func (r *roundRobinSelector) Close() error {
+	return nil
+}
+
+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
+	}
+
+	return &roundRobinSelector{sopts}
+}

selector/roundrobin/round_robin_selector_test.go

@@ -0,0 +1,33 @@
+package roundrobin
+
+import (
+	"testing"
+
+	"github.com/micro/go-micro/registry/mock"
+	"github.com/micro/go-micro/selector"
+)
+
+func TestRoundRobinSelector(t *testing.T) {
+	counts := map[string]int{}
+
+	rr := &roundRobinSelector{
+		so: selector.Options{
+			Registry: mock.NewRegistry(),
+		},
+	}
+
+	next, err := rr.Select("foo")
+	if err != nil {
+		t.Errorf("Unexpected error calling rr 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("Round Robin Counts %v", counts)
+}

selector/selector.go

@@ -0,0 +1,93 @@
+/*
+The Selector package provides a way to algorithmically filter and return
+nodes required by the client or any other system. Selector's implemented
+by Micro build on the registry but it's of optional use. One could
+provide a static Selector that has a fixed pool.
+
+	func (r *randomSelector) Select(service string, opts ...SelectOption) (Next, error) {
+		var sopts SelectOptions
+		for _, opt := range opts {
+			opt(&sopts)
+		}
+
+		// get the service
+		services, err := r.so.Registry.GetService(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, ErrNotFound
+		}
+
+		var nodes []*registry.Node
+
+		for _, service := range services {
+			for _, node := range service.Nodes {
+				nodes = append(nodes, node)
+			}
+		}
+
+		if len(nodes) == 0 {
+			return nil, ErrNotFound
+		}
+
+		return func() (*registry.Node, error) {
+			i := rand.Int()
+			j := i % len(services)
+
+			if len(services[j].Nodes) == 0 {
+				return nil, ErrNotFound
+			}
+
+			k := i % len(services[j].Nodes)
+			return services[j].Nodes[k], nil
+		}, nil
+	}
+
+
+*/
+package selector
+
+import (
+	"errors"
+	"github.com/micro/go-micro/registry"
+)
+
+// Selector builds on the registry as a mechanism to pick nodes
+// and mark their status. This allows host pools and other things
+// to be built using various algorithms.
+type Selector interface {
+	// Select returns a function which should return the next node
+	Select(service string, opts ...SelectOption) (Next, error)
+	// Mark sets the success/error against a node
+	Mark(service string, node *registry.Node, err error)
+	// Reset returns state back to zero for a service
+	Reset(service string)
+	// Close renders the selector unusable
+	Close() error
+}
+
+// Next is a function that returns the next node
+// based on the selector's algorithm
+type Next func() (*registry.Node, error)
+
+// SelectFilter is used to filter a service during the selection process
+type SelectFilter func([]*registry.Service) []*registry.Service
+
+var (
+	DefaultSelector = newRandomSelector()
+
+	ErrNotFound      = errors.New("not found")
+	ErrNoneAvailable = errors.New("none available")
+)
+
+func NewSelector(opts ...Option) Selector {
+	return newRandomSelector(opts...)
+}