ocastore.go

// 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.

package internal // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/prometheusreceiver/internal"

import (
	"context"
	"errors"
	"sync/atomic"
	"time"

	"github.com/prometheus/prometheus/model/exemplar"
	"github.com/prometheus/prometheus/model/labels"
	"github.com/prometheus/prometheus/scrape"
	"github.com/prometheus/prometheus/storage"
	"go.opentelemetry.io/collector/component"
	"go.opentelemetry.io/collector/config"
	"go.opentelemetry.io/collector/consumer"
)

const (
	runningStateInit = iota
	runningStateReady
	runningStateStop
)

var idSeq int64
var noop = &noopAppender{}

// OcaStore translates Prometheus scraping diffs into OpenCensus format.
type OcaStore struct {
	ctx context.Context

	running              int32 // access atomically
	sink                 consumer.Metrics
	mc                   *metadataService
	jobsMap              *JobsMapPdata
	useStartTimeMetric   bool
	startTimeMetricRegex string
	receiverID           config.ComponentID
	externalLabels       labels.Labels

	settings component.ReceiverCreateSettings
}

// NewOcaStore returns an ocaStore instance, which can be acted as prometheus' scrape.Appendable
func NewOcaStore(
	ctx context.Context,
	sink consumer.Metrics,
	set component.ReceiverCreateSettings,
	gcInterval time.Duration,
	useStartTimeMetric bool,
	startTimeMetricRegex string,
	receiverID config.ComponentID,
	externalLabels labels.Labels) *OcaStore {
	var jobsMap *JobsMapPdata
	if !useStartTimeMetric {
		jobsMap = NewJobsMapPdata(gcInterval)
	}
	return &OcaStore{
		running:              runningStateInit,
		ctx:                  ctx,
		sink:                 sink,
		settings:             set,
		jobsMap:              jobsMap,
		useStartTimeMetric:   useStartTimeMetric,
		startTimeMetricRegex: startTimeMetricRegex,
		receiverID:           receiverID,
		externalLabels:       externalLabels,
	}
}

// SetScrapeManager is used to config the underlying scrape.Manager as it's needed for OcaStore, otherwise OcaStore
// cannot accept any Appender() request
func (o *OcaStore) SetScrapeManager(scrapeManager *scrape.Manager) {
	if scrapeManager != nil && atomic.CompareAndSwapInt32(&o.running, runningStateInit, runningStateReady) {
		o.mc = &metadataService{sm: scrapeManager}
	}
}

func (o *OcaStore) Appender(context.Context) storage.Appender {
	state := atomic.LoadInt32(&o.running)
	if state == runningStateReady {
		return newTransactionPdata(
			o.ctx,
			&txConfig{
				jobsMap:              o.jobsMap,
				useStartTimeMetric:   o.useStartTimeMetric,
				startTimeMetricRegex: o.startTimeMetricRegex,
				receiverID:           o.receiverID,
				ms:                   o.mc,
				sink:                 o.sink,
				externalLabels:       o.externalLabels,
				settings:             o.settings,
			},
		)
	} else if state == runningStateInit {
		panic("ScrapeManager is not set")
	}
	// instead of returning an error, return a dummy appender instead, otherwise it can trigger panic
	return noop
}

// Close OcaStore as well as the internal metadataService.
func (o *OcaStore) Close() {
	if atomic.CompareAndSwapInt32(&o.running, runningStateReady, runningStateStop) {
		o.mc.Close()
	}
}

// noopAppender, always return error on any operations
type noopAppender struct{}

var errAlreadyStopped = errors.New("already stopped")

func (*noopAppender) Append(storage.SeriesRef, labels.Labels, int64, float64) (storage.SeriesRef, error) {
	return 0, errAlreadyStopped
}

func (*noopAppender) AppendExemplar(ref storage.SeriesRef, l labels.Labels, e exemplar.Exemplar) (storage.SeriesRef, error) {
	return 0, errAlreadyStopped
}

func (*noopAppender) Commit() error {
	return errAlreadyStopped
}

func (*noopAppender) Rollback() error {
	return nil
}