Allow custom view.Meters to export metrics for other Resources (#1212)

* Remove call to time.Now() on worker thread when handling record reqs (#1210)

Time is already recorded on the client side and stored in the currently unused recordReq.t
field. Avoiding these repeated calls to time.Now while the worker is blocked can significantly
reduce worker contention.

* Update Meter to track and report Resource for metric data.

Co-authored-by: Ian Milligan <ianmllgn@gmail.com>

stats/view/view_to_metric.go

@@ -18,6 +18,8 @@ package view
 import (
 	"time"
 
+	"go.opencensus.io/resource"
+
 	"go.opencensus.io/metric/metricdata"
 	"go.opencensus.io/stats"
 )
@@ -125,7 +127,7 @@ func rowToTimeseries(v *viewInternal, row *Row, now time.Time, startTime time.Ti
 	}
 }
 
-func viewToMetric(v *viewInternal, now time.Time, startTime time.Time) *metricdata.Metric {
+func viewToMetric(v *viewInternal, r *resource.Resource, now time.Time, startTime time.Time) *metricdata.Metric {
 	if v.metricDescriptor.Type == metricdata.TypeGaugeInt64 ||
 		v.metricDescriptor.Type == metricdata.TypeGaugeFloat64 {
 		startTime = time.Time{}
@@ -144,6 +146,7 @@ func viewToMetric(v *viewInternal, now time.Time, startTime time.Time) *metricda
 	m := &metricdata.Metric{
 		Descriptor: *v.metricDescriptor,
 		TimeSeries: ts,
+		Resource:   r,
 	}
 	return m
 }

stats/view/view_to_metric_test.go

@@ -447,7 +447,7 @@ func Test_ViewToMetric(t *testing.T) {
 			tc.vi.addSample(tag.FromContext(ctx), v, nil, now)
 		}
 
-		gotMetric := viewToMetric(tc.vi, now, startTime)
+		gotMetric := viewToMetric(tc.vi, nil, now, startTime)
 		if !cmp.Equal(gotMetric, tc.wantMetric) {
 			// JSON format is strictly for checking the content when test fails. Do not use JSON
 			// format to determine if the two values are same as it doesn't differentiate between
@@ -509,7 +509,7 @@ func TestUnitConversionForAggCount(t *testing.T) {
 
 	for _, tc := range tests {
 		tc.vi.addSample(tag.FromContext(context.Background()), 5.0, nil, now)
-		gotMetric := viewToMetric(tc.vi, now, startTime)
+		gotMetric := viewToMetric(tc.vi, nil, now, startTime)
 		gotUnit := gotMetric.Descriptor.Unit
 		if !cmp.Equal(gotUnit, tc.wantUnit) {
 			t.Errorf("Verify Unit: %s: Got:%v Want:%v", tc.name, gotUnit, tc.wantUnit)

stats/view/worker.go

@@ -20,6 +20,8 @@ import (
 	"sync"
 	"time"
 
+	"go.opencensus.io/resource"
+
 	"go.opencensus.io/metric/metricdata"
 	"go.opencensus.io/metric/metricproducer"
 	"go.opencensus.io/stats"
@@ -47,6 +49,7 @@ type worker struct {
 	c          chan command
 	quit, done chan bool
 	mu         sync.RWMutex
+	r          *resource.Resource
 
 	exportersMu sync.RWMutex
 	exporters   map[Exporter]struct{}
@@ -91,6 +94,10 @@ type Meter interface {
 	RegisterExporter(Exporter)
 	// UnregisterExporter unregisters an exporter.
 	UnregisterExporter(Exporter)
+	// SetResource may be used to set the Resource associated with this registry.
+	// This is intended to be used in cases where a single process exports metrics
+	// for multiple Resources, typically in a multi-tenant situation.
+	SetResource(*resource.Resource)
 
 	// Start causes the Meter to start processing Record calls and aggregating
 	// statistics as well as exporting data.
@@ -249,6 +256,14 @@ func NewMeter() Meter {
 	}
 }
 
+// SetResource associates all data collected by this Meter with the specified
+// resource. This resource is reported when using metricexport.ReadAndExport;
+// it is not provided when used with ExportView/RegisterExporter, because that
+// interface does not provide a means for reporting the Resource.
+func (w *worker) SetResource(r *resource.Resource) {
+	w.r = r
+}
+
 func (w *worker) Start() {
 	go w.start()
 }
@@ -371,7 +386,7 @@ func (w *worker) toMetric(v *viewInternal, now time.Time) *metricdata.Metric {
 		startTime = w.startTimes[v]
 	}
 
-	return viewToMetric(v, now, startTime)
+	return viewToMetric(v, w.r, now, startTime)
 }
 
 // Read reads all view data and returns them as metrics.

stats/view/worker_test.go

@@ -18,10 +18,13 @@ package view
 import (
 	"context"
 	"errors"
+	"sort"
 	"sync"
 	"testing"
 	"time"
 
+	"go.opencensus.io/resource"
+
 	"go.opencensus.io/metric/metricdata"
 	"go.opencensus.io/metric/metricexport"
 	"go.opencensus.io/stats"
@@ -123,8 +126,13 @@ func Test_Worker_MultiExport(t *testing.T) {
 
 	// This test reports the same data for the default worker and a secondary
 	// worker, and ensures that the stats are kept independently.
+	extraResource := resource.Resource{
+		Type:   "additional",
+		Labels: map[string]string{"key1": "value1", "key2": "value2"},
+	}
 	worker2 := NewMeter().(*worker)
 	worker2.Start()
+	worker2.SetResource(&extraResource)
 
 	m := stats.Float64("Test_Worker_MultiExport/MF1", "desc MF1", "unit")
 	key := tag.MustNewKey(("key"))
@@ -162,50 +170,62 @@ func Test_Worker_MultiExport(t *testing.T) {
 		}
 	}
 
-	wantRows := []struct {
-		w    Meter
-		view string
-		rows []*Row
-	}{{
-		view: count.Name,
-		rows: []*Row{
+	makeKey := func(r *resource.Resource, view string) string {
+		if r == nil {
+			r = &resource.Resource{}
+		}
+		return resource.EncodeLabels(r.Labels) + "/" + view
+	}
+
+	// Format is Resource.Labels encoded as string, then
+	wantPartialData := map[string][]*Row{
+		makeKey(nil, count.Name): []*Row{
 			{[]tag.Tag{{Key: key, Value: "a"}}, &CountData{Value: 2}},
 			{[]tag.Tag{{Key: key, Value: "b"}}, &CountData{Value: 1}},
 		},
-	}, {
-		view: sum.Name,
-		rows: []*Row{
-			{nil, &SumData{Value: 7.5}}},
-	}, {
-		w:    worker2,
-		view: count.Name,
-		rows: []*Row{
+		makeKey(nil, sum.Name): []*Row{
+			{nil, &SumData{Value: 7.5}},
+		},
+		makeKey(&extraResource, count.Name): []*Row{
 			{[]tag.Tag{{Key: key, Value: "b"}}, &CountData{Value: 1}},
 		},
-	}}
+	}
 
-	for _, wantRow := range wantRows {
-		retrieve := RetrieveData
-		if wantRow.w != nil {
-			retrieve = wantRow.w.(*worker).RetrieveData
-		}
-		gotRows, err := retrieve(wantRow.view)
-		if err != nil {
-			t.Fatalf("RetrieveData(%v), got error %v", wantRow.view, err)
+	te := &testExporter{}
+	metricexport.NewReader().ReadAndExport(te)
+	for _, m := range te.metrics {
+		key := makeKey(m.Resource, m.Descriptor.Name)
+		want, ok := wantPartialData[key]
+		if !ok {
+			t.Errorf("Unexpected data for %q: %v", key, m)
+			continue
 		}
-		for _, got := range gotRows {
-			if !containsRow(wantRow.rows, got) {
-				t.Errorf("%s: got row %#v; want none", wantRow.view, got)
-				break
+		gotTs := m.TimeSeries
+		sort.Sort(byLabel(gotTs))
+
+		for i, ts := range gotTs {
+			for j, label := range ts.LabelValues {
+				if want[i].Tags[j].Value != label.Value {
+					t.Errorf("Mismatched tag values (want %q, got %q) for %v in %q", want[i].Tags[j].Value, label.Value, ts, key)
+				}
 			}
-		}
-		for _, want := range wantRow.rows {
-			if !containsRow(gotRows, want) {
-				t.Errorf("%s: got none, want %#v", wantRow.view, want)
-				break
+			switch wantValue := want[i].Data.(type) {
+			case *CountData:
+				got := ts.Points[0].Value.(int64)
+				if wantValue.Value != got {
+					t.Errorf("Mismatched value (want %d, got %d) for %v in %q", wantValue, got, ts, key)
+				}
+			case *SumData:
+				got := ts.Points[0].Value.(float64)
+				if wantValue.Value != got {
+					t.Errorf("Mismatched value (want %f, got %f) for %v in %q", wantValue, got, ts, key)
+				}
+			default:
+				t.Errorf("Unexpected type of data: %T for %v in %q", wantValue, want[i], key)
 			}
 		}
 	}
+
 	// Verify that worker has not been computing sum:
 	got, err := worker2.RetrieveData(sum.Name)
 	if err == nil {
@@ -577,9 +597,11 @@ func TestWorkerRace(t *testing.T) {
 }
 
 type testExporter struct {
+	metrics []*metricdata.Metric
 }
 
 func (te *testExporter) ExportMetrics(ctx context.Context, metrics []*metricdata.Metric) error {
+	te.metrics = metrics
 	return nil
 }
 
@@ -619,3 +641,20 @@ func restart() {
 	defaultWorker = NewMeter().(*worker)
 	go defaultWorker.start()
 }
+
+// byTag implements sort.Interface for *metricdata.TimeSeries by Labels.
+type byLabel []*metricdata.TimeSeries
+
+func (ts byLabel) Len() int      { return len(ts) }
+func (ts byLabel) Swap(i, j int) { ts[i], ts[j] = ts[j], ts[i] }
+func (ts byLabel) Less(i, j int) bool {
+	if len(ts[i].LabelValues) != len(ts[j].LabelValues) {
+		return len(ts[i].LabelValues) < len(ts[j].LabelValues)
+	}
+	for k := range ts[i].LabelValues {
+		if ts[i].LabelValues[k].Value != ts[j].LabelValues[k].Value {
+			return ts[i].LabelValues[k].Value < ts[j].LabelValues[k].Value
+		}
+	}
+	return false
+}