Return tagged metrics registry from metrics.FromContext call.

metrics/context.go

@@ -22,10 +22,22 @@ func WithRegistry(ctx context.Context, registry Registry) context.Context {
 }
 
 func FromContext(ctx context.Context) Registry {
-	if registry, ok := ctx.Value(registryKey).(Registry); ok {
+	registry, ok := ctx.Value(registryKey).(Registry)
+	if !ok {
+		registry = DefaultMetricsRegistry
+	}
+	rootRegistry, ok := registry.(*rootRegistry)
+	if !ok {
+		return registry
+	}
+	tagsContainer, ok := ctx.Value(tagsKey).(*tagsContainer)
+	if !ok {
 		return registry
 	}
-	return DefaultMetricsRegistry
+	return &childRegistry{
+		root: rootRegistry,
+		tags: tagsContainer.Tags,
+	}
 }
 
 // AddTags adds the provided tags to the provided context. If the provided context already has tag storage, the new tags

metrics/context_test.go

@@ -23,6 +23,21 @@ func TestFromContext(t *testing.T) {
 	assert.Equal(t, FromContext(ctx), reg)
 }
 
+func TestFromContextWithTags(t *testing.T) {
+	ctx := context.Background()
+	reg := &rootRegistry{
+		registry: metrics.NewPrefixedRegistry("foo"),
+	}
+
+	ctx = WithRegistry(ctx, reg)
+	ctx = AddTags(ctx, MustNewTag("bar", "baz"))
+
+	assert.Equal(t, FromContext(ctx), &childRegistry{
+		root: reg,
+		tags: Tags{MustNewTag("bar", "baz")},
+	})
+}
+
 func TestDefaultFromContext(t *testing.T) {
 	ctx := context.Background()
 	assert.Equal(t, FromContext(ctx), DefaultMetricsRegistry)