Add OpenCensus metrics registration functionality to core

core/metrics/register.go

@@ -0,0 +1,70 @@
+package metrics
+
+import (
+	"fmt"
+	"sync"
+
+	"go.opencensus.io/stats/view"
+)
+
+var registeredViews = map[string][]*view.View{}
+var mu = new(sync.Mutex)
+
+type ErrNamespace struct {
+	Namespace string
+}
+
+// ErrUnregisteredNamespace is an error for lookup of requested unregistered Namespace
+type ErrUnregisteredNamespace ErrNamespace
+
+func (e ErrUnregisteredNamespace) Error() string {
+	return fmt.Sprintf("no views found registered under Namespace %s", e.Namespace)
+}
+
+// ErrDuplicateNamespaceRegistration is an error for a Namespace that has already
+// registered views
+type ErrDuplicateNamespaceRegistration ErrNamespace
+
+func (e ErrDuplicateNamespaceRegistration) Error() string {
+	return fmt.Sprintf("duplicate registration of views by Namespace %s", e.Namespace)
+}
+
+// RegisterViews accepts a namespace and a slice of Views, which will be registered
+// with opencensus and maintained in the global registered views map
+func RegisterViews(namespace string, views ...*view.View) error {
+	mu.Lock()
+	defer mu.Unlock()
+	_, ok := registeredViews[namespace]
+	if ok {
+		return ErrDuplicateNamespaceRegistration{Namespace: namespace}
+	} else {
+		registeredViews[namespace] = views
+	}
+
+	return nil
+}
+
+// LookupViews returns all views for a Namespace name. Returns an error if the
+// Namespace has not been registered.
+func LookupViews(name string) ([]*view.View, error) {
+	mu.Lock()
+	defer mu.Unlock()
+	views, ok := registeredViews[name]
+	if !ok {
+		return nil, ErrUnregisteredNamespace{Namespace: name}
+	}
+	response := make([]*view.View, len(views))
+	copy(response, views)
+	return response, nil
+}
+
+// AllViews returns all registered views as a single slice
+func AllViews() []*view.View {
+	var views []*view.View
+	mu.Lock()
+	defer mu.Unlock()
+	for _, vs := range registeredViews {
+		views = append(views, vs...)
+	}
+	return views
+}

core/metrics/register_test.go

@@ -0,0 +1,94 @@
+package metrics
+
+import (
+	"fmt"
+	"go.opencensus.io/stats"
+	"testing"
+
+	"go.opencensus.io/stats/view"
+)
+
+func newTestMeasure(name string) stats.Measure {
+	return stats.Int64(fmt.Sprintf("test/measure/%s", name),
+		fmt.Sprintf("Test measurement %s", name),
+		stats.UnitDimensionless,
+	)
+}
+
+func newTestView(name string) *view.View {
+	return &view.View{
+		Name:        fmt.Sprintf("test/%s", name),
+		Description: fmt.Sprintf("Test view %s", name),
+		Measure:     newTestMeasure(name),
+		Aggregation: view.LastValue(),
+	}
+}
+
+func TestRegisteringViews(t *testing.T) {
+	registeredViews = make(map[string][]*view.View)
+
+	t.Run("test registering first views", func(t *testing.T) {
+		testView := newTestView("empty-map-0")
+
+		if err := RegisterViews("test", testView); err != nil {
+			t.Fatal("unable to register view in empty map", err)
+		}
+	})
+
+	t.Run("test registering with existing views", func(t *testing.T) {
+		testView := newTestView("empty-map-1")
+		testView2 := newTestView("existing-entity-0")
+
+		if err := RegisterViews("test2", testView); err != nil {
+			t.Fatal("unable to register view in empty map", err)
+		}
+		if err := RegisterViews("test3", testView2); err != nil {
+			t.Fatal("unable to register view in map", err)
+		}
+	})
+
+	t.Run("test registering duplicate views", func(t *testing.T) {
+		testView := newTestView("empty-map-2")
+		testView2 := newTestView("existing-entity-1")
+
+		if err := RegisterViews("test4", testView); err != nil {
+			t.Fatal("unable to register view in empty map", err)
+		}
+		if err := RegisterViews("test4", testView2); err == nil {
+			t.Fatal("allowed duplicate view registration")
+		}
+	})
+
+	t.Run("test looking up views", func(t *testing.T) {
+		testView := newTestView("empty-map-3")
+
+		if err := RegisterViews("test5", testView); err != nil {
+			t.Fatal("unable to register view in empty map", err)
+		}
+
+		views, err := LookupViews("test5")
+		if err != nil {
+			t.Fatal("error looking up views", err)
+		}
+
+		if views[0].Name != testView.Name {
+			t.Fatal("incorrect view lookup, received name:", views[0].Name)
+		}
+	})
+}
+
+func TestAllViews(t *testing.T) {
+	registeredViews = make(map[string][]*view.View)
+	t.Run("test retrieving all views", func(t *testing.T) {
+		views := []*view.View{newTestView("all-views-0"), newTestView("all-views-1"), newTestView("all-views-2")}
+
+		if err := RegisterViews("test6", views...); err != nil {
+			t.Fatal("unable to register multiple views at once", err)
+		}
+
+		allViews := AllViews()
+		if len(allViews) != len(views) {
+			t.Fatalf("didn't receive equal number of views: %d %d", len(views), len(allViews))
+		}
+	})
+}