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/kv/kv_test.go

@@ -0,0 +1,119 @@
+package kv
+
+import (
+	"errors"
+	"path"
+	"testing"
+	"time"
+
+	"github.com/docker/docker/pkg/discovery"
+	"github.com/docker/libkv/store"
+	libkvmock "github.com/docker/libkv/store/mock"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+)
+
+func TestInitialize(t *testing.T) {
+	storeMock, err := libkvmock.New([]string{"127.0.0.1"}, nil)
+	assert.NotNil(t, storeMock)
+	assert.NoError(t, err)
+
+	d := &Discovery{backend: store.CONSUL}
+	d.Initialize("127.0.0.1", 0, 0)
+	d.store = storeMock
+
+	s := d.store.(*libkvmock.Mock)
+	assert.Len(t, s.Endpoints, 1)
+	assert.Equal(t, s.Endpoints[0], "127.0.0.1")
+	assert.Equal(t, d.path, discoveryPath)
+
+	storeMock, err = libkvmock.New([]string{"127.0.0.1:1234"}, nil)
+	assert.NotNil(t, storeMock)
+	assert.NoError(t, err)
+
+	d = &Discovery{backend: store.CONSUL}
+	d.Initialize("127.0.0.1:1234/path", 0, 0)
+	d.store = storeMock
+
+	s = d.store.(*libkvmock.Mock)
+	assert.Len(t, s.Endpoints, 1)
+	assert.Equal(t, s.Endpoints[0], "127.0.0.1:1234")
+	assert.Equal(t, d.path, "path/"+discoveryPath)
+
+	storeMock, err = libkvmock.New([]string{"127.0.0.1:1234", "127.0.0.2:1234", "127.0.0.3:1234"}, nil)
+	assert.NotNil(t, storeMock)
+	assert.NoError(t, err)
+
+	d = &Discovery{backend: store.CONSUL}
+	d.Initialize("127.0.0.1:1234,127.0.0.2:1234,127.0.0.3:1234/path", 0, 0)
+	d.store = storeMock
+
+	s = d.store.(*libkvmock.Mock)
+	if assert.Len(t, s.Endpoints, 3) {
+		assert.Equal(t, s.Endpoints[0], "127.0.0.1:1234")
+		assert.Equal(t, s.Endpoints[1], "127.0.0.2:1234")
+		assert.Equal(t, s.Endpoints[2], "127.0.0.3:1234")
+	}
+	assert.Equal(t, d.path, "path/"+discoveryPath)
+}
+
+func TestWatch(t *testing.T) {
+	storeMock, err := libkvmock.New([]string{"127.0.0.1:1234"}, nil)
+	assert.NotNil(t, storeMock)
+	assert.NoError(t, err)
+
+	d := &Discovery{backend: store.CONSUL}
+	d.Initialize("127.0.0.1:1234/path", 0, 0)
+	d.store = storeMock
+
+	s := d.store.(*libkvmock.Mock)
+	mockCh := make(chan []*store.KVPair)
+
+	// The first watch will fail.
+	s.On("WatchTree", "path/"+discoveryPath, mock.Anything).Return(mockCh, errors.New("test error")).Once()
+	// The second one will succeed.
+	s.On("WatchTree", "path/"+discoveryPath, mock.Anything).Return(mockCh, nil).Once()
+	expected := discovery.Entries{
+		&discovery.Entry{Host: "1.1.1.1", Port: "1111"},
+		&discovery.Entry{Host: "2.2.2.2", Port: "2222"},
+	}
+	kvs := []*store.KVPair{
+		{Key: path.Join("path", discoveryPath, "1.1.1.1"), Value: []byte("1.1.1.1:1111")},
+		{Key: path.Join("path", discoveryPath, "2.2.2.2"), Value: []byte("2.2.2.2:2222")},
+	}
+
+	stopCh := make(chan struct{})
+	ch, errCh := d.Watch(stopCh)
+
+	// It should fire an error since the first WatchTree call failed.
+	assert.EqualError(t, <-errCh, "test error")
+	// We have to drain the error channel otherwise Watch will get stuck.
+	go func() {
+		for range errCh {
+		}
+	}()
+
+	// Push the entries into the store channel and make sure discovery emits.
+	mockCh <- kvs
+	assert.Equal(t, <-ch, expected)
+
+	// Add a new entry.
+	expected = append(expected, &discovery.Entry{Host: "3.3.3.3", Port: "3333"})
+	kvs = append(kvs, &store.KVPair{Key: path.Join("path", discoveryPath, "3.3.3.3"), Value: []byte("3.3.3.3:3333")})
+	mockCh <- kvs
+	assert.Equal(t, <-ch, expected)
+
+	// Make sure that if an error occurs it retries.
+	// This third call to WatchTree will be checked later by AssertExpectations.
+	s.On("WatchTree", "path/"+discoveryPath, mock.Anything).Return(mockCh, nil)
+	close(mockCh)
+	// Give it enough time to call WatchTree.
+	time.Sleep(3)
+
+	// Stop and make sure it closes all channels.
+	close(stopCh)
+	assert.Nil(t, <-ch)
+	assert.Nil(t, <-errCh)
+
+	s.AssertExpectations(t)
+}