processor.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 cumulativetodeltaprocessor

import (
	"context"
	"math"

	"go.opentelemetry.io/collector/model/pdata"
	"go.uber.org/zap"

	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/cumulativetodeltaprocessor/internal/tracking"
)

type cumulativeToDeltaProcessor struct {
	metrics         map[string]struct{}
	logger          *zap.Logger
	deltaCalculator *tracking.MetricTracker
	cancelFunc      context.CancelFunc
}

func newCumulativeToDeltaProcessor(config *Config, logger *zap.Logger) *cumulativeToDeltaProcessor {
	ctx, cancel := context.WithCancel(context.Background())
	p := &cumulativeToDeltaProcessor{
		logger:          logger,
		deltaCalculator: tracking.NewMetricTracker(ctx, logger, config.MaxStaleness),
		cancelFunc:      cancel,
	}
	if len(config.Metrics) > 0 {
		p.metrics = make(map[string]struct{}, len(config.Metrics))
		for _, m := range config.Metrics {
			p.metrics[m] = struct{}{}
		}
	}
	return p
}

// processMetrics implements the ProcessMetricsFunc type.
func (ctdp *cumulativeToDeltaProcessor) processMetrics(_ context.Context, md pdata.Metrics) (pdata.Metrics, error) {
	resourceMetricsSlice := md.ResourceMetrics()
	resourceMetricsSlice.RemoveIf(func(rm pdata.ResourceMetrics) bool {
		ilms := rm.InstrumentationLibraryMetrics()
		ilms.RemoveIf(func(ilm pdata.InstrumentationLibraryMetrics) bool {
			ms := ilm.Metrics()
			ms.RemoveIf(func(m pdata.Metric) bool {
				if _, ok := ctdp.metrics[m.Name()]; !ok {
					return false
				}
				switch m.DataType() {
				case pdata.MetricDataTypeSum:
					ms := m.Sum()
					if ms.AggregationTemporality() != pdata.MetricAggregationTemporalityCumulative {
						return false
					}

					// Ignore any metrics that aren't monotonic
					if !ms.IsMonotonic() {
						return false
					}

					baseIdentity := tracking.MetricIdentity{
						Resource:               rm.Resource(),
						InstrumentationLibrary: ilm.InstrumentationLibrary(),
						MetricDataType:         m.DataType(),
						MetricName:             m.Name(),
						MetricUnit:             m.Unit(),
						MetricIsMonotonic:      ms.IsMonotonic(),
					}
					ctdp.convertDataPoints(ms.DataPoints(), baseIdentity)
					ms.SetAggregationTemporality(pdata.MetricAggregationTemporalityDelta)
					return ms.DataPoints().Len() == 0
				default:
					return false
				}
			})
			return ilm.Metrics().Len() == 0
		})
		return rm.InstrumentationLibraryMetrics().Len() == 0
	})
	return md, nil
}

func (ctdp *cumulativeToDeltaProcessor) shutdown(context.Context) error {
	ctdp.cancelFunc()
	return nil
}

func (ctdp *cumulativeToDeltaProcessor) convertDataPoints(in interface{}, baseIdentity tracking.MetricIdentity) {
	switch dps := in.(type) {
	case pdata.NumberDataPointSlice:
		dps.RemoveIf(func(dp pdata.NumberDataPoint) bool {
			id := baseIdentity
			id.StartTimestamp = dp.StartTimestamp()
			id.Attributes = dp.Attributes()
			id.MetricValueType = dp.Type()
			point := tracking.ValuePoint{
				ObservedTimestamp: dp.Timestamp(),
			}
			if id.IsFloatVal() {
				// Do not attempt to transform NaN values
				if math.IsNaN(dp.DoubleVal()) {
					return false
				}
				point.FloatValue = dp.DoubleVal()
			} else {
				point.IntValue = dp.IntVal()
			}
			trackingPoint := tracking.MetricPoint{
				Identity: id,
				Value:    point,
			}
			delta, valid := ctdp.deltaCalculator.Convert(trackingPoint)

			// When converting non-monotonic cumulative counters,
			// the first data point is omitted since the initial
			// reference is not assumed to be zero
			if !valid {
				return true
			}
			dp.SetStartTimestamp(delta.StartTimestamp)
			if id.IsFloatVal() {
				dp.SetDoubleVal(delta.FloatValue)
			} else {
				dp.SetIntVal(delta.IntValue)
			}
			return false
		})
	}
}