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periodic_reader.go
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periodic_reader.go
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// Copyright The OpenTelemetry 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.
//go:build go1.17
// +build go1.17
package metric // import "go.opentelemetry.io/otel/sdk/metric"
import (
"context"
"fmt"
"sync"
"sync/atomic"
"time"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/internal/global"
"go.opentelemetry.io/otel/sdk/metric/export"
)
// Default periodic reader timing.
const (
defaultTimeout = time.Millisecond * 30000
defaultInterval = time.Millisecond * 60000
)
// periodicReaderConfig contains configuration options for a PeriodicReader.
type periodicReaderConfig struct {
interval time.Duration
timeout time.Duration
}
// newPeriodicReaderConfig returns a periodicReaderConfig configured with
// options.
func newPeriodicReaderConfig(options []PeriodicReaderOption) periodicReaderConfig {
c := periodicReaderConfig{
interval: defaultInterval,
timeout: defaultTimeout,
}
for _, o := range options {
c = o.apply(c)
}
return c
}
// PeriodicReaderOption applies a configuration option value to a PeriodicReader.
type PeriodicReaderOption interface {
apply(periodicReaderConfig) periodicReaderConfig
}
// periodicReaderOptionFunc applies a set of options to a periodicReaderConfig.
type periodicReaderOptionFunc func(periodicReaderConfig) periodicReaderConfig
// apply returns a periodicReaderConfig with option(s) applied.
func (o periodicReaderOptionFunc) apply(conf periodicReaderConfig) periodicReaderConfig {
return o(conf)
}
// WithTimeout configures the time a PeriodicReader waits for an export to
// complete before canceling it.
//
// If this option is not used or d is less than or equal to zero, 30 seconds
// is used as the default.
func WithTimeout(d time.Duration) PeriodicReaderOption {
return periodicReaderOptionFunc(func(conf periodicReaderConfig) periodicReaderConfig {
if d <= 0 {
return conf
}
conf.timeout = d
return conf
})
}
// WithInterval configures the intervening time between exports for a
// PeriodicReader.
//
// If this option is not used or d is less than or equal to zero, 60 seconds
// is used as the default.
func WithInterval(d time.Duration) PeriodicReaderOption {
return periodicReaderOptionFunc(func(conf periodicReaderConfig) periodicReaderConfig {
if d <= 0 {
return conf
}
conf.interval = d
return conf
})
}
// NewPeriodicReader returns a Reader that collects and exports metric data to
// the exporter at a defined interval. By default, the returned Reader will
// collect and export data every 60 seconds, and will cancel export attempts
// that exceed 30 seconds. The export time is not counted towards the interval
// between attempts.
//
// The Collect method of the returned Reader continues to gather and return
// metric data to the user. It will not automatically send that data to the
// exporter. That is left to the user to accomplish.
func NewPeriodicReader(exporter Exporter, options ...PeriodicReaderOption) Reader {
conf := newPeriodicReaderConfig(options)
ctx, cancel := context.WithCancel(context.Background())
r := &periodicReader{
timeout: conf.timeout,
exporter: exporter,
cancel: cancel,
}
r.wg.Add(1)
go func() {
defer r.wg.Done()
r.run(ctx, conf.interval)
}()
return r
}
// periodicReader is a Reader that continuously collects and exports metric
// data at a set interval.
type periodicReader struct {
producer atomic.Value
timeout time.Duration
exporter Exporter
wg sync.WaitGroup
cancel context.CancelFunc
shutdownOnce sync.Once
}
// newTicker allows testing override.
var newTicker = time.NewTicker
// run continuously collects and exports metric data at the specified
// interval. This will run until ctx is canceled or times out.
func (r *periodicReader) run(ctx context.Context, interval time.Duration) {
ticker := newTicker(interval)
defer ticker.Stop()
for {
select {
case <-ticker.C:
m, err := r.Collect(ctx)
if err == nil {
c, cancel := context.WithTimeout(ctx, r.timeout)
err = r.exporter.Export(c, m)
cancel()
}
if err != nil {
otel.Handle(err)
}
case <-ctx.Done():
return
}
}
}
// register registers p as the producer of this reader.
func (r *periodicReader) register(p producer) {
// Only register once. If producer is already set, do nothing.
if !r.producer.CompareAndSwap(nil, produceHolder{produce: p.produce}) {
msg := "did not register periodic reader"
global.Error(errDuplicateRegister, msg)
}
}
// Collect gathers and returns all metric data related to the Reader from
// the SDK. The returned metric data is not exported to the configured
// exporter, it is left to the caller to handle that if desired.
//
// An error is returned if this is called after Shutdown.
func (r *periodicReader) Collect(ctx context.Context) (export.Metrics, error) {
p := r.producer.Load()
if p == nil {
return export.Metrics{}, ErrReaderNotRegistered
}
ph, ok := p.(produceHolder)
if !ok {
// The atomic.Value is entirely in the periodicReader's control so
// this should never happen. In the unforeseen case that this does
// happen, return an error instead of panicking so a users code does
// not halt in the processes.
err := fmt.Errorf("periodic reader: invalid producer: %T", p)
return export.Metrics{}, err
}
return ph.produce(ctx)
}
// ForceFlush flushes the Exporter.
func (r *periodicReader) ForceFlush(ctx context.Context) error {
return r.exporter.ForceFlush(ctx)
}
// Shutdown stops the export pipeline.
func (r *periodicReader) Shutdown(ctx context.Context) error {
err := ErrReaderShutdown
r.shutdownOnce.Do(func() {
// Stop the run loop.
r.cancel()
r.wg.Wait()
// Any future call to Collect will now return ErrReaderShutdown.
r.producer.Store(produceHolder{
produce: shutdownProducer{}.produce,
})
err = r.exporter.Shutdown(ctx)
})
return err
}