// 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
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
package view
import (
"fmt"
"time"
"go.opencensus.io/stats"
"go.opencensus.io/stats/internal"
"go.opencensus.io/tag"
)
func init() {
defaultWorker = newWorker()
go defaultWorker.start()
internal.DefaultRecorder = record
}
type measureRef struct {
measure string
views map[*viewInternal]struct{}
}
type worker struct {
measures map[string]*measureRef
views map[string]*viewInternal
startTimes map[*viewInternal]time.Time
timer *time.Ticker
c chan command
quit, done chan bool
}
var defaultWorker *worker
var defaultReportingDuration = 10 * time.Second
// Find returns a registered view associated with this name.
// If no registered view is found, nil is returned.
func Find(name string) (v *View) {
req := &getViewByNameReq{
name: name,
c: make(chan *getViewByNameResp),
}
defaultWorker.c <- req
resp := <-req.c
return resp.v
}
// Register begins collecting data for the given views.
// Once a view is registered, it reports data to the registered exporters.
func Register(views ...*View) error {
for _, v := range views {
if err := v.canonicalize(); err != nil {
return err
}
}
req := ®isterViewReq{
views: views,
err: make(chan error),
}
defaultWorker.c <- req
return <-req.err
}
// Unregister the given views. Data will not longer be exported for these views
// after Unregister returns.
// It is not necessary to unregister from views you expect to collect for the
// duration of your program execution.
func Unregister(views ...*View) {
names := make([]string, len(views))
for i := range views {
names[i] = views[i].Name
}
req := &unregisterFromViewReq{
views: names,
done: make(chan struct{}),
}
defaultWorker.c <- req
<-req.done
}
// RetrieveData gets a snapshot of the data collected for the the view registered
// with the given name. It is intended for testing only.
func RetrieveData(viewName string) ([]*Row, error) {
req := &retrieveDataReq{
now: time.Now(),
v: viewName,
c: make(chan *retrieveDataResp),
}
defaultWorker.c <- req
resp := <-req.c
return resp.rows, resp.err
}
func record(tags *tag.Map, ms interface{}, attachments map[string]string) {
req := &recordReq{
tm: tags,
ms: ms.([]stats.Measurement),
attachments: attachments,
t: time.Now(),
}
defaultWorker.c <- req
}
// SetReportingPeriod sets the interval between reporting aggregated views in
// the program. If duration is less than or equal to zero, it enables the
// default behavior.
//
// Note: each exporter makes different promises about what the lowest supported
// duration is. For example, the Stackdriver exporter recommends a value no
// lower than 1 minute. Consult each exporter per your needs.
func SetReportingPeriod(d time.Duration) {
// TODO(acetechnologist): ensure that the duration d is more than a certain
// value. e.g. 1s
req := &setReportingPeriodReq{
d: d,
c: make(chan bool),
}
defaultWorker.c <- req
<-req.c // don't return until the timer is set to the new duration.
}
func newWorker() *worker {
return &worker{
measures: make(map[string]*measureRef),
views: make(map[string]*viewInternal),
startTimes: make(map[*viewInternal]time.Time),
timer: time.NewTicker(defaultReportingDuration),
c: make(chan command, 1024),
quit: make(chan bool),
done: make(chan bool),
}
}
func (w *worker) start() {
for {
select {
case cmd := <-w.c:
cmd.handleCommand(w)
case <-w.timer.C:
w.reportUsage(time.Now())
case <-w.quit:
w.timer.Stop()
close(w.c)
w.done <- true
return
}
}
}
func (w *worker) stop() {
w.quit <- true
<-w.done
}
func (w *worker) getMeasureRef(name string) *measureRef {
if mr, ok := w.measures[name]; ok {
return mr
}
mr := &measureRef{
measure: name,
views: make(map[*viewInternal]struct{}),
}
w.measures[name] = mr
return mr
}
func (w *worker) tryRegisterView(v *View) (*viewInternal, error) {
vi, err := newViewInternal(v)
if err != nil {
return nil, err
}
if x, ok := w.views[vi.view.Name]; ok {
if !x.view.same(vi.view) {
return nil, fmt.Errorf("cannot register view %q; a different view with the same name is already registered", v.Name)
}
// the view is already registered so there is nothing to do and the
// command is considered successful.
return x, nil
}
w.views[vi.view.Name] = vi
ref := w.getMeasureRef(vi.view.Measure.Name())
ref.views[vi] = struct{}{}
return vi, nil
}
func (w *worker) reportView(v *viewInternal, now time.Time) {
if !v.isSubscribed() {
return
}
rows := v.collectedRows()
_, ok := w.startTimes[v]
if !ok {
w.startTimes[v] = now
}
viewData := &Data{
View: v.view,
Start: w.startTimes[v],
End: time.Now(),
Rows: rows,
}
exportersMu.Lock()
for e := range exporters {
e.ExportView(viewData)
}
exportersMu.Unlock()
}
func (w *worker) reportUsage(now time.Time) {
for _, v := range w.views {
w.reportView(v, now)
}
}
