Add pkg/discovery for nodes discovery

Absorb Swarm's discovery package in order to provide a common node
discovery mechanism to be used by both Swarm and networking code.

Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>

discovery/nodes/nodes.go

@@ -0,0 +1,54 @@
+package nodes
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/docker/docker/pkg/discovery"
+)
+
+// Discovery is exported
+type Discovery struct {
+	entries discovery.Entries
+}
+
+func init() {
+	Init()
+}
+
+// Init is exported
+func Init() {
+	discovery.Register("nodes", &Discovery{})
+}
+
+// Initialize is exported
+func (s *Discovery) Initialize(uris string, _ time.Duration, _ time.Duration) error {
+	for _, input := range strings.Split(uris, ",") {
+		for _, ip := range discovery.Generate(input) {
+			entry, err := discovery.NewEntry(ip)
+			if err != nil {
+				return fmt.Errorf("%s, please check you are using the correct discovery (missing token:// ?)", err.Error())
+			}
+			s.entries = append(s.entries, entry)
+		}
+	}
+
+	return nil
+}
+
+// Watch is exported
+func (s *Discovery) Watch(stopCh <-chan struct{}) (<-chan discovery.Entries, <-chan error) {
+	ch := make(chan discovery.Entries)
+	go func() {
+		defer close(ch)
+		ch <- s.entries
+		<-stopCh
+	}()
+	return ch, nil
+}
+
+// Register is exported
+func (s *Discovery) Register(addr string) error {
+	return discovery.ErrNotImplemented
+}

discovery/nodes/nodes_test.go

@@ -0,0 +1,43 @@
+package nodes
+
+import (
+	"testing"
+
+	"github.com/docker/docker/pkg/discovery"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestInitialize(t *testing.T) {
+	d := &Discovery{}
+	d.Initialize("1.1.1.1:1111,2.2.2.2:2222", 0, 0)
+	assert.Equal(t, len(d.entries), 2)
+	assert.Equal(t, d.entries[0].String(), "1.1.1.1:1111")
+	assert.Equal(t, d.entries[1].String(), "2.2.2.2:2222")
+}
+
+func TestInitializeWithPattern(t *testing.T) {
+	d := &Discovery{}
+	d.Initialize("1.1.1.[1:2]:1111,2.2.2.[2:4]:2222", 0, 0)
+	assert.Equal(t, len(d.entries), 5)
+	assert.Equal(t, d.entries[0].String(), "1.1.1.1:1111")
+	assert.Equal(t, d.entries[1].String(), "1.1.1.2:1111")
+	assert.Equal(t, d.entries[2].String(), "2.2.2.2:2222")
+	assert.Equal(t, d.entries[3].String(), "2.2.2.3:2222")
+	assert.Equal(t, d.entries[4].String(), "2.2.2.4:2222")
+}
+
+func TestWatch(t *testing.T) {
+	d := &Discovery{}
+	d.Initialize("1.1.1.1:1111,2.2.2.2:2222", 0, 0)
+	expected := discovery.Entries{
+		&discovery.Entry{Host: "1.1.1.1", Port: "1111"},
+		&discovery.Entry{Host: "2.2.2.2", Port: "2222"},
+	}
+	ch, _ := d.Watch(nil)
+	assert.True(t, expected.Equals(<-ch))
+}
+
+func TestRegister(t *testing.T) {
+	d := &Discovery{}
+	assert.Error(t, d.Register("0.0.0.0"))
+}