worker: SplitClone: Display correct list of used tablets during online clone phase.

Before the shown list was empty.

go/vt/worker/split_clone.go

@@ -168,6 +168,14 @@ func (scw *SplitCloneWorker) setErrorState(err error) {
 	event.DispatchUpdate(scw.ev, "error: "+err.Error())
 }
 
+func (scw *SplitCloneWorker) formatOnlineSources() string {
+	aliases := scw.tabletTracker.TabletsInUse()
+	if aliases == "" {
+		return "no online source tablets currently in use"
+	}
+	return aliases
+}
+
 func (scw *SplitCloneWorker) setFormattedOfflineSources(aliases []*topodatapb.TabletAlias) {
 	scw.formattedOfflineSourcesMu.Lock()
 	defer scw.formattedOfflineSourcesMu.Unlock()
@@ -200,7 +208,7 @@ func (scw *SplitCloneWorker) StatusAsHTML() template.HTML {
 	switch state {
 	case WorkerStateCloneOnline:
 		result += "<b>Running:</b></br>\n"
-		result += "<b>Copying from:</b> " + scw.FormattedOfflineSources() + "</br>\n"
+		result += "<b>Copying from:</b> " + scw.formatOnlineSources() + "</br>\n"
 		statuses, eta := scw.tableStatusListOnline.format()
 		result += "<b>ETA:</b> " + eta.String() + "</br>\n"
 		result += strings.Join(statuses, "</br>\n")
@@ -244,7 +252,7 @@ func (scw *SplitCloneWorker) StatusAsText() string {
 	switch state {
 	case WorkerStateCloneOnline:
 		result += "Running:\n"
-		result += "Copying from: " + scw.FormattedOfflineSources() + "\n"
+		result += "Copying from: " + scw.formatOnlineSources() + "\n"
 		statuses, eta := scw.tableStatusListOffline.format()
 		result += "ETA: " + eta.String() + "\n"
 		result += strings.Join(statuses, "\n")

go/vt/worker/tablet_tracker.go

@@ -7,6 +7,7 @@ package worker
 import (
 	"fmt"
 	"sort"
+	"strings"
 	"sync"
 
 	"github.com/youtube/vitess/go/vt/discovery"
@@ -84,6 +85,20 @@ func (t *TabletTracker) Untrack(alias *topodata.TabletAlias) {
 	}
 }
 
+// TabletsInUse returns a string of all tablet aliases currently in use.
+// The tablets are separated by a space.
+func (t *TabletTracker) TabletsInUse() string {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	var aliases []string
+	for alias := range t.usedTablets {
+		aliases = append(aliases, alias)
+	}
+	sort.Strings(aliases)
+	return strings.Join(aliases, " ")
+}
+
 func (t *TabletTracker) tabletsByUsage() []string {
 	sorted := sortMapByValue(t.usedTablets)
 	var tablets []string

go/vt/worker/tablet_tracker_test.go

@@ -0,0 +1,60 @@
+// Copyright 2016, Google Inc. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package worker
+
+import (
+	"testing"
+
+	"github.com/golang/protobuf/proto"
+	"github.com/youtube/vitess/go/vt/discovery"
+	"github.com/youtube/vitess/go/vt/topo"
+
+	querypb "github.com/youtube/vitess/go/vt/proto/query"
+	topodatapb "github.com/youtube/vitess/go/vt/proto/topodata"
+)
+
+var ts1 = discovery.TabletStats{
+	Tablet: topo.NewTablet(10, "cell", "host1"),
+	Target: &querypb.Target{Keyspace: "k", Shard: "s", TabletType: topodatapb.TabletType_REPLICA},
+}
+var ts2 = discovery.TabletStats{
+	Tablet: topo.NewTablet(20, "cell", "host1"),
+	Target: &querypb.Target{Keyspace: "k", Shard: "s", TabletType: topodatapb.TabletType_REPLICA},
+}
+var allTs = []discovery.TabletStats{ts1, ts2}
+
+func TestTabletsInUse(t *testing.T) {
+	tt := NewTabletTracker()
+
+	tt.Track([]discovery.TabletStats{ts1})
+	if got, want := tt.TabletsInUse(), "cell-0000000010"; got != want {
+		t.Fatalf("TabletsInUse() = %v, want = %v", got, want)
+	}
+
+	tt.Track([]discovery.TabletStats{ts2})
+	if got, want := tt.TabletsInUse(), "cell-0000000010 cell-0000000020"; got != want {
+		t.Fatalf("TabletsInUse() = %v, want = %v", got, want)
+	}
+}
+
+func TestTrackUntrack(t *testing.T) {
+	tt := NewTabletTracker()
+	// ts1 will be used because no tablet is in use yet and ts1 is the first.
+	if got, want := tt.Track(allTs), ts1.Tablet.Alias; !proto.Equal(got, want) {
+		t.Fatalf("Track(%v) = %v, want = %v", allTs, got, want)
+	}
+
+	// ts1 is already in use once, use ts2 now.
+	if got, want := tt.Track(allTs), ts2.Tablet.Alias; !proto.Equal(got, want) {
+		t.Fatalf("Track(%v) = %v, want = %v", allTs, got, want)
+	}
+
+	// ts2 is no longer in use after Untrack().
+	tt.Untrack(ts2.Tablet.Alias)
+	// ts2 instead of ts1 will be used because ts1 has a higher use count.
+	if got, want := tt.Track(allTs), ts2.Tablet.Alias; !proto.Equal(got, want) {
+		t.Fatalf("Track(%v) = %v, want = %v", allTs, got, want)
+	}
+}