Reimplement prometheus exporter

exporter/prometheusexporter/README.md

@@ -16,6 +16,7 @@ The following settings can be optionally configured:
 - `namespace` (no default): if set, exports metrics under the provided value.
 - `send_timestamps` (default = `false`): if true, sends the timestamp of the underlying
   metric sample in the response.
+- `metric_expiration` (default = `5m`): defines how long metrics are exposed without updates
 
 Example:
 
@@ -28,4 +29,5 @@ exporters:
       label1: value1
       "another label": spaced value
     send_timestamps: true
+    metric_expiration: 180m
 ```

exporter/prometheusexporter/accumulator.go

@@ -0,0 +1,365 @@
+// 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 prometheusexporter
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+	"time"
+
+	"go.uber.org/zap"
+
+	"go.opentelemetry.io/collector/consumer/pdata"
+)
+
+type accumulatedValue struct {
+	// value contains a metric with exactly one aggregated datapoint
+	value pdata.Metric
+	// stored indicates when metric was stored
+	stored time.Time
+
+	instrumentationLibrary pdata.InstrumentationLibrary
+}
+
+// accumulator stores aggragated values of incoming metrics
+type accumulator interface {
+	// Accumulate stores aggragated metric values
+	Accumulate(resourceMetrics pdata.ResourceMetrics) (processed int)
+	// Collect returns a slice with relevant aggregated metrics
+	Collect() (metrics []pdata.Metric)
+}
+
+// LastValueAccumulator keeps last value for accumulated metrics
+type lastValueAccumulator struct {
+	logger *zap.Logger
+
+	registeredMetrics sync.Map
+
+	// metricExpiration contains duration for which metric
+	// should be served after it was stored
+	metricExpiration time.Duration
+}
+
+// NewAccumulator returns LastValueAccumulator
+func newAccumulator(logger *zap.Logger, metricExpiration time.Duration) accumulator {
+	return &lastValueAccumulator{
+		logger:           logger,
+		metricExpiration: metricExpiration,
+	}
+}
+
+// Accumulate stores one datapoint per metric
+func (a *lastValueAccumulator) Accumulate(rm pdata.ResourceMetrics) (n int) {
+	ilms := rm.InstrumentationLibraryMetrics()
+
+	for i := 0; i < ilms.Len(); i++ {
+		ilm := ilms.At(i)
+
+		metrics := ilm.Metrics()
+		for j := 0; j < metrics.Len(); j++ {
+			n += a.addMetric(metrics.At(j), ilm.InstrumentationLibrary())
+		}
+	}
+
+	return
+}
+
+func (a *lastValueAccumulator) addMetric(metric pdata.Metric, il pdata.InstrumentationLibrary) int {
+	a.logger.Debug(fmt.Sprintf("accumulating metric: %s", metric.Name()))
+
+	switch metric.DataType() {
+	case pdata.MetricDataTypeIntGauge:
+		return a.accumulateIntGauge(metric, il)
+	case pdata.MetricDataTypeIntSum:
+		return a.accumulateIntSum(metric, il)
+	case pdata.MetricDataTypeDoubleGauge:
+		return a.accumulateDoubleGauge(metric, il)
+	case pdata.MetricDataTypeDoubleSum:
+		return a.accumulateDoubleSum(metric, il)
+	case pdata.MetricDataTypeIntHistogram:
+		return a.accumulateIntHistogram(metric, il)
+	case pdata.MetricDataTypeDoubleHistogram:
+		return a.accumulateDoubleHistogram(metric, il)
+	}
+
+	return 0
+}
+
+func (a *lastValueAccumulator) accumulateIntGauge(metric pdata.Metric, il pdata.InstrumentationLibrary) (n int) {
+	dps := metric.IntGauge().DataPoints()
+	for i := 0; i < dps.Len(); i++ {
+		ip := dps.At(i)
+
+		ts := ip.Timestamp().AsTime()
+		signature := timeseriesSignature(il.Name(), metric, ip.LabelsMap())
+
+		v, ok := a.registeredMetrics.Load(signature)
+		if !ok {
+			m := createMetric(metric)
+			m.IntGauge().DataPoints().Append(ip)
+			a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+			n++
+			continue
+		}
+		mv := v.(*accumulatedValue)
+
+		if ts.Before(mv.value.IntGauge().DataPoints().At(0).Timestamp().AsTime()) {
+			// only keep datapoint with latest timestamp
+			continue
+		}
+
+		m := createMetric(metric)
+		m.IntGauge().DataPoints().Append(ip)
+		a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+		n++
+	}
+	return
+}
+
+func (a *lastValueAccumulator) accumulateDoubleGauge(metric pdata.Metric, il pdata.InstrumentationLibrary) (n int) {
+	dps := metric.DoubleGauge().DataPoints()
+	for i := 0; i < dps.Len(); i++ {
+		ip := dps.At(i)
+
+		ts := ip.Timestamp().AsTime()
+		signature := timeseriesSignature(il.Name(), metric, ip.LabelsMap())
+
+		v, ok := a.registeredMetrics.Load(signature)
+		if !ok {
+			m := createMetric(metric)
+			m.DoubleGauge().DataPoints().Append(ip)
+			a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+			n++
+			continue
+		}
+		mv := v.(*accumulatedValue)
+
+		if ts.Before(mv.value.DoubleGauge().DataPoints().At(0).Timestamp().AsTime()) {
+			// only keep datapoint with latest timestamp
+			continue
+		}
+
+		m := createMetric(metric)
+		m.DoubleGauge().DataPoints().Append(ip)
+		a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+		n++
+	}
+	return
+}
+
+func (a *lastValueAccumulator) accumulateIntSum(metric pdata.Metric, il pdata.InstrumentationLibrary) (n int) {
+	intSum := metric.IntSum()
+
+	// Drop metrics with non-cumulative aggregations
+	if intSum.AggregationTemporality() != pdata.AggregationTemporalityCumulative {
+		return
+	}
+
+	dps := intSum.DataPoints()
+	for i := 0; i < dps.Len(); i++ {
+		ip := dps.At(i)
+
+		ts := ip.Timestamp().AsTime()
+		signature := timeseriesSignature(il.Name(), metric, ip.LabelsMap())
+
+		v, ok := a.registeredMetrics.Load(signature)
+		if !ok {
+			m := createMetric(metric)
+			m.IntSum().SetIsMonotonic(metric.IntSum().IsMonotonic())
+			m.IntSum().SetAggregationTemporality(pdata.AggregationTemporalityCumulative)
+			m.IntSum().DataPoints().Append(ip)
+			a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+			n++
+			continue
+		}
+		mv := v.(*accumulatedValue)
+
+		if ts.Before(mv.value.IntSum().DataPoints().At(0).Timestamp().AsTime()) {
+			// only keep datapoint with latest timestamp
+			continue
+		}
+
+		m := createMetric(metric)
+		m.IntSum().SetIsMonotonic(metric.IntSum().IsMonotonic())
+		m.IntSum().SetAggregationTemporality(pdata.AggregationTemporalityCumulative)
+		m.IntSum().DataPoints().Append(ip)
+		a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+		n++
+	}
+	return
+}
+
+func (a *lastValueAccumulator) accumulateDoubleSum(metric pdata.Metric, il pdata.InstrumentationLibrary) (n int) {
+	doubleSum := metric.DoubleSum()
+
+	// Drop metrics with non-cumulative aggregations
+	if doubleSum.AggregationTemporality() != pdata.AggregationTemporalityCumulative {
+		return
+	}
+
+	dps := doubleSum.DataPoints()
+	for i := 0; i < dps.Len(); i++ {
+		ip := dps.At(i)
+
+		ts := ip.Timestamp().AsTime()
+		signature := timeseriesSignature(il.Name(), metric, ip.LabelsMap())
+
+		v, ok := a.registeredMetrics.Load(signature)
+		if !ok {
+			m := createMetric(metric)
+			m.DoubleSum().SetIsMonotonic(metric.DoubleSum().IsMonotonic())
+			m.DoubleSum().SetAggregationTemporality(pdata.AggregationTemporalityCumulative)
+			m.DoubleSum().DataPoints().Append(ip)
+			a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+			n++
+			continue
+		}
+		mv := v.(*accumulatedValue)
+
+		if ts.Before(mv.value.DoubleSum().DataPoints().At(0).Timestamp().AsTime()) {
+			// only keep datapoint with latest timestamp
+			continue
+		}
+
+		m := createMetric(metric)
+		m.DoubleSum().SetIsMonotonic(metric.DoubleSum().IsMonotonic())
+		m.DoubleSum().SetAggregationTemporality(pdata.AggregationTemporalityCumulative)
+		m.DoubleSum().DataPoints().Append(ip)
+		a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+		n++
+	}
+	return
+}
+
+func (a *lastValueAccumulator) accumulateIntHistogram(metric pdata.Metric, il pdata.InstrumentationLibrary) (n int) {
+	intHistogram := metric.IntHistogram()
+
+	// Drop metrics with non-cumulative aggregations
+	if intHistogram.AggregationTemporality() != pdata.AggregationTemporalityCumulative {
+		return
+	}
+
+	dps := intHistogram.DataPoints()
+	for i := 0; i < dps.Len(); i++ {
+		ip := dps.At(i)
+
+		ts := ip.Timestamp().AsTime()
+		signature := timeseriesSignature(il.Name(), metric, ip.LabelsMap())
+
+		v, ok := a.registeredMetrics.Load(signature)
+		if !ok {
+			m := createMetric(metric)
+			m.IntHistogram().DataPoints().Append(ip)
+			a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+			n++
+			continue
+		}
+		mv := v.(*accumulatedValue)
+
+		if ts.Before(mv.value.IntHistogram().DataPoints().At(0).Timestamp().AsTime()) {
+			// only keep datapoint with latest timestamp
+			continue
+		}
+
+		m := createMetric(metric)
+		m.IntHistogram().DataPoints().Append(ip)
+		m.IntHistogram().SetAggregationTemporality(pdata.AggregationTemporalityCumulative)
+		a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+		n++
+	}
+	return
+}
+
+func (a *lastValueAccumulator) accumulateDoubleHistogram(metric pdata.Metric, il pdata.InstrumentationLibrary) (n int) {
+	doubleHistogram := metric.DoubleHistogram()
+
+	// Drop metrics with non-cumulative aggregations
+	if doubleHistogram.AggregationTemporality() != pdata.AggregationTemporalityCumulative {
+		return
+	}
+
+	dps := doubleHistogram.DataPoints()
+	for i := 0; i < dps.Len(); i++ {
+		ip := dps.At(i)
+
+		ts := ip.Timestamp().AsTime()
+		signature := timeseriesSignature(il.Name(), metric, ip.LabelsMap())
+
+		v, ok := a.registeredMetrics.Load(signature)
+		if !ok {
+			m := createMetric(metric)
+			m.DoubleHistogram().DataPoints().Append(ip)
+			a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+			n++
+			continue
+		}
+		mv := v.(*accumulatedValue)
+
+		if ts.Before(mv.value.DoubleHistogram().DataPoints().At(0).Timestamp().AsTime()) {
+			// only keep datapoint with latest timestamp
+			continue
+		}
+
+		m := createMetric(metric)
+		m.DoubleHistogram().DataPoints().Append(ip)
+		m.DoubleHistogram().SetAggregationTemporality(pdata.AggregationTemporalityCumulative)
+		a.registeredMetrics.Store(signature, &accumulatedValue{value: m, instrumentationLibrary: il, stored: time.Now()})
+		n++
+	}
+	return
+}
+
+// Collect returns a slice with relevant aggregated metrics
+func (a *lastValueAccumulator) Collect() []pdata.Metric {
+	a.logger.Debug("Accumulator collect called")
+
+	res := make([]pdata.Metric, 0)
+
+	a.registeredMetrics.Range(func(key, value interface{}) bool {
+		v := value.(*accumulatedValue)
+		if time.Now().After(v.stored.Add(a.metricExpiration)) {
+			a.logger.Debug(fmt.Sprintf("metric expired: %s", v.value.Name()))
+			a.registeredMetrics.Delete(key)
+			return true
+		}
+
+		res = append(res, v.value)
+		return true
+	})
+
+	return res
+}
+
+func timeseriesSignature(ilmName string, metric pdata.Metric, labels pdata.StringMap) string {
+	var b strings.Builder
+	b.WriteString(metric.DataType().String())
+	b.WriteString("*" + ilmName)
+	b.WriteString("*" + metric.Name())
+	labels.ForEach(func(k string, v string) {
+		b.WriteString("*" + k + "*" + v)
+	})
+	return b.String()
+}
+
+func createMetric(metric pdata.Metric) pdata.Metric {
+	m := pdata.NewMetric()
+	m.SetName(metric.Name())
+	m.SetDescription(metric.Description())
+	m.SetUnit(metric.Unit())
+	m.SetDataType(metric.DataType())
+
+	return m
+}