blob: c2a08af6784c416ca5ef16933b4fdc8d84732fe7 [file] [log] [blame]
// Copyright 2017, OpenCensus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package view
import (
// View allows users to aggregate the recorded stats.Measurements.
// Views need to be passed to the Register function to be before data will be
// collected and sent to Exporters.
type View struct {
Name string // Name of View. Must be unique. If unset, will default to the name of the Measure.
Description string // Description is a human-readable description for this view.
// TagKeys are the tag keys describing the grouping of this view.
// A single Row will be produced for each combination of associated tag values.
TagKeys []tag.Key
// Measure is a stats.Measure to aggregate in this view.
Measure stats.Measure
// Aggregation is the aggregation function tp apply to the set of Measurements.
Aggregation *Aggregation
// WithName returns a copy of the View with a new name. This is useful for
// renaming views to cope with limitations placed on metric names by various
// backends.
func (v *View) WithName(name string) *View {
vNew := *v
vNew.Name = name
return &vNew
// same compares two views and returns true if they represent the same aggregation.
func (v *View) same(other *View) bool {
if v == other {
return true
if v == nil {
return false
return reflect.DeepEqual(v.Aggregation, other.Aggregation) &&
v.Measure.Name() == other.Measure.Name()
// canonicalize canonicalizes v by setting explicit
// defaults for Name and Description and sorting the TagKeys
func (v *View) canonicalize() error {
if v.Measure == nil {
return fmt.Errorf("cannot register view %q: measure not set", v.Name)
if v.Aggregation == nil {
return fmt.Errorf("cannot register view %q: aggregation not set", v.Name)
if v.Name == "" {
v.Name = v.Measure.Name()
if v.Description == "" {
v.Description = v.Measure.Description()
if err := checkViewName(v.Name); err != nil {
return err
sort.Slice(v.TagKeys, func(i, j int) bool {
return v.TagKeys[i].Name() < v.TagKeys[j].Name()
return nil
// viewInternal is the internal representation of a View.
type viewInternal struct {
view *View // view is the canonicalized View definition associated with this view.
subscribed uint32 // 1 if someone is subscribed and data need to be exported, use atomic to access
collector *collector
func newViewInternal(v *View) (*viewInternal, error) {
return &viewInternal{
view: v,
collector: &collector{make(map[string]AggregationData), v.Aggregation},
}, nil
func (v *viewInternal) subscribe() {
atomic.StoreUint32(&v.subscribed, 1)
func (v *viewInternal) unsubscribe() {
atomic.StoreUint32(&v.subscribed, 0)
// isSubscribed returns true if the view is exporting
// data by subscription.
func (v *viewInternal) isSubscribed() bool {
return atomic.LoadUint32(&v.subscribed) == 1
func (v *viewInternal) clearRows() {
func (v *viewInternal) collectedRows() []*Row {
return v.collector.collectedRows(v.view.TagKeys)
func (v *viewInternal) addSample(m *tag.Map, e *exemplar.Exemplar) {
if !v.isSubscribed() {
sig := string(encodeWithKeys(m, v.view.TagKeys))
v.collector.addSample(sig, e)
// A Data is a set of rows about usage of the single measure associated
// with the given view. Each row is specific to a unique set of tags.
type Data struct {
View *View
Start, End time.Time
Rows []*Row
// Row is the collected value for a specific set of key value pairs a.k.a tags.
type Row struct {
Tags []tag.Tag
Data AggregationData
func (r *Row) String() string {
var buffer bytes.Buffer
buffer.WriteString("{ ")
buffer.WriteString("{ ")
for _, t := range r.Tags {
buffer.WriteString(fmt.Sprintf("{%v %v}", t.Key.Name(), t.Value))
buffer.WriteString(" }")
buffer.WriteString(fmt.Sprintf("%v", r.Data))
buffer.WriteString(" }")
return buffer.String()
// Equal returns true if both rows are equal. Tags are expected to be ordered
// by the key name. Even both rows have the same tags but the tags appear in
// different orders it will return false.
func (r *Row) Equal(other *Row) bool {
if r == other {
return true
return reflect.DeepEqual(r.Tags, other.Tags) && r.Data.equal(other.Data)
func checkViewName(name string) error {
if len(name) > internal.MaxNameLength {
return fmt.Errorf("view name cannot be larger than %v", internal.MaxNameLength)
if !internal.IsPrintable(name) {
return fmt.Errorf("view name needs to be an ASCII string")
return nil