Fix issues with initial start time and restarts in the Prometheus receiver. (#598)

* Updates dependencies to use dinooliva/promreceiver

* Adds metrics_asjuster for dealing with inital time series values and restarts.

* Updates code to conform to contribution specs.

* Update MetricsAdjuster to handle resets appropriately

* Apply gofmt to non-conforming files

* Make metrics adjustment configurable

* Apply gofmt to metrics_receiver

* Fix all issues related to fmt/vet/lint

* Extend unit tests to include multiple simultaneous metrics and timeseries

* Add unit test for implicit/explicit empty label values; rename vars for readability

* Clarify naming (latest -> previous) for timeseriesinfo

Author: dinooliva

receiver/prometheusreceiver/internal/metrics_adjuster.go

@@ -0,0 +1,220 @@
+package internal
+
+import (
+	"fmt"
+	metricspb "github.com/census-instrumentation/opencensus-proto/gen-go/metrics/v1"
+	"github.com/golang/protobuf/ptypes/wrappers"
+	"go.uber.org/zap"
+	"strings"
+)
+
+type timeseriesinfo struct {
+	initial  *metricspb.TimeSeries
+	previous *metricspb.TimeSeries
+}
+
+type metricsInstanceMap map[string]*timeseriesinfo
+
+func newMetricsInstanceMap() *metricsInstanceMap {
+	mim := metricsInstanceMap(make(map[string]*timeseriesinfo))
+	return &mim
+}
+
+func (mim *metricsInstanceMap) get(metric *metricspb.Metric, values []*metricspb.LabelValue) *timeseriesinfo {
+	name := metric.GetMetricDescriptor().GetName()
+	sig := getSignature(name, values)
+	tsi, ok := (*mim)[sig]
+	if !ok {
+		tsi = &timeseriesinfo{}
+		(*mim)[sig] = tsi
+	}
+	return tsi
+}
+
+// create a unique signature consisting of a metric's name and label values
+func getSignature(name string, values []*metricspb.LabelValue) string {
+	labelValues := make([]string, 0, len(values))
+	for _, label := range values {
+		if label.GetValue() != "" {
+			labelValues = append(labelValues, label.GetValue())
+		}
+	}
+	return fmt.Sprintf("%s,%s", name, strings.Join(labelValues, ","))
+}
+
+// JobsMap maps from a job instance to a map of metric instances for the job.
+type JobsMap map[string]*metricsInstanceMap
+
+// NewJobsMap creates a new (empty) JobsMap.
+func NewJobsMap() *JobsMap {
+	jm := JobsMap(make(map[string]*metricsInstanceMap))
+	return &jm
+}
+
+func (jm *JobsMap) get(job, instance string) *metricsInstanceMap {
+	sig := job + ":" + instance
+	metricsMap, ok := (*jm)[sig]
+	if !ok {
+		metricsMap = newMetricsInstanceMap()
+		(*jm)[sig] = metricsMap
+	}
+	return metricsMap
+}
+
+// MetricsAdjuster takes a map from a metric instance to the initial point in the metrics instance
+// and provides AdjustMetrics, which takes a sequence of metrics and adjust their values based on
+// the initial points.
+type MetricsAdjuster struct {
+	metricsMap *metricsInstanceMap
+	logger     *zap.SugaredLogger
+}
+
+// NewMetricsAdjuster is a constructor for MetricsAdjuster.
+func NewMetricsAdjuster(metricsMap *metricsInstanceMap, logger *zap.SugaredLogger) *MetricsAdjuster {
+	return &MetricsAdjuster{
+		metricsMap: metricsMap,
+		logger:     logger,
+	}
+}
+
+// AdjustMetrics takes a sequence of metrics and adjust their values based on the initial points in the
+// metricsMap. If the metric is the first point in the timeseries, or the timeseries has been reset, it is
+// removed from the sequence and added to the the metricsMap.
+func (ma *MetricsAdjuster) AdjustMetrics(metrics []*metricspb.Metric) []*metricspb.Metric {
+	var adjusted = make([]*metricspb.Metric, 0, len(metrics))
+	for _, metric := range metrics {
+		if ma.adjustMetric(metric) {
+			adjusted = append(adjusted, metric)
+		}
+	}
+	return adjusted
+}
+
+// returns true if at least one of the metric's timeseries was adjusted and false if all of the timeseries are an initial occurence or a reset.
+// Types of metrics returned supported by prometheus:
+// - MetricDescriptor_GAUGE_DOUBLE
+// - MetricDescriptor_GAUGE_DISTRIBUTION
+// - MetricDescriptor_CUMULATIVE_DOUBLE
+// - MetricDescriptor_CUMULATIVE_DISTRIBUTION
+// - MetricDescriptor_SUMMARY
+func (ma *MetricsAdjuster) adjustMetric(metric *metricspb.Metric) bool {
+	switch metric.MetricDescriptor.Type {
+	case metricspb.MetricDescriptor_GAUGE_DOUBLE, metricspb.MetricDescriptor_GAUGE_DISTRIBUTION:
+		// gauges don't need to be adjusted so no additional processing is necessary
+		return true
+	default:
+		return ma.adjustMetricTimeseries(metric)
+	}
+}
+
+// Returns true if at least one of the metric's timeseries was adjusted and false if all of the timeseries are an initial occurence or a reset.
+func (ma *MetricsAdjuster) adjustMetricTimeseries(metric *metricspb.Metric) bool {
+	filtered := make([]*metricspb.TimeSeries, 0, len(metric.GetTimeseries()))
+	for _, current := range metric.GetTimeseries() {
+		tsi := ma.metricsMap.get(metric, current.GetLabelValues())
+		if tsi.initial == nil {
+			// initial timeseries
+			tsi.initial = current
+			tsi.previous = current
+		} else {
+			if ma.adjustTimeseries(metric.MetricDescriptor.Type, current, tsi.initial, tsi.previous) {
+				tsi.previous = current
+				filtered = append(filtered, current)
+			} else {
+				// reset timeseries
+				tsi.initial = current
+				tsi.previous = current
+			}
+		}
+	}
+	metric.Timeseries = filtered
+	return len(filtered) > 0
+}
+
+// returns true if 'current' was adjusted and false if 'current' is an the initial occurence or a reset of the timeseries.
+func (ma *MetricsAdjuster) adjustTimeseries(metricType metricspb.MetricDescriptor_Type, current, initial, previous *metricspb.TimeSeries) bool {
+	if !ma.adjustPoints(metricType, current.GetPoints(), initial.GetPoints(), previous.GetPoints()) {
+		return false
+	}
+	current.StartTimestamp = initial.StartTimestamp
+	return true
+}
+
+func (ma *MetricsAdjuster) adjustPoints(metricType metricspb.MetricDescriptor_Type, current, initial, previous []*metricspb.Point) bool {
+	if len(current) != 1 || len(initial) != 1 || len(current) != 1 {
+		ma.logger.Infof("len(current): %v, len(initial): %v, len(previous): %v should all be 1", len(current), len(initial), len(previous))
+		return true
+	}
+	return ma.adjustPoint(metricType, current[0], initial[0], previous[0])
+}
+
+// Note: There is an important, subtle point here. When a new timeseries or a reset is detected, current and initial are the same object.
+// When initial == previous, the previous value/count/sum are all the initial value. When initial != previous, the previous value/count/sum has
+// been adjusted wrt the initial value so both they must be combined to find the actual previous value/count/sum. This happens because the
+// timeseries are updated in-place - if new copies of the timeseries were created instead, previous could be used directly but this would
+// mean reallocating all of the metrics.
+func (ma *MetricsAdjuster) adjustPoint(metricType metricspb.MetricDescriptor_Type, current, initial, previous *metricspb.Point) bool {
+	switch metricType {
+	case metricspb.MetricDescriptor_CUMULATIVE_DOUBLE:
+		currentValue := current.GetDoubleValue()
+		initialValue := initial.GetDoubleValue()
+		previousValue := initialValue
+		if initial != previous {
+			previousValue += previous.GetDoubleValue()
+		}
+		if currentValue < previousValue {
+			// reset detected
+			return false
+		}
+		current.Value = &metricspb.Point_DoubleValue{DoubleValue: currentValue - initialValue}
+	case metricspb.MetricDescriptor_CUMULATIVE_DISTRIBUTION:
+		// note: sum of squared deviation not currently supported
+		currentDist := current.GetDistributionValue()
+		initialDist := initial.GetDistributionValue()
+		previousCount := initialDist.Count
+		previousSum := initialDist.Sum
+		if initial != previous {
+			previousCount += previous.GetDistributionValue().Count
+			previousSum += previous.GetDistributionValue().Sum
+		}
+		if currentDist.Count < previousCount || currentDist.Sum < previousSum {
+			// reset detected
+			return false
+		}
+		currentDist.Count -= initialDist.Count
+		currentDist.Sum -= initialDist.Sum
+		ma.adjustBuckets(currentDist.Buckets, initialDist.Buckets)
+	case metricspb.MetricDescriptor_SUMMARY:
+		// note: for summary, we don't adjust the snapshot
+		currentCount := current.GetSummaryValue().Count.GetValue()
+		currentSum := current.GetSummaryValue().Sum.GetValue()
+		initialCount := initial.GetSummaryValue().Count.GetValue()
+		initialSum := initial.GetSummaryValue().Sum.GetValue()
+		previousCount := initialCount
+		previousSum := initialSum
+		if initial != previous {
+			previousCount += previous.GetSummaryValue().Count.GetValue()
+			previousSum += previous.GetSummaryValue().Sum.GetValue()
+		}
+		if currentCount < previousCount || currentSum < previousSum {
+			// reset detected
+			return false
+		}
+		current.GetSummaryValue().Count = &wrappers.Int64Value{Value: currentCount - initialCount}
+		current.GetSummaryValue().Sum = &wrappers.DoubleValue{Value: currentSum - initialSum}
+	default:
+		// this shouldn't happen
+		ma.logger.Infof("adjust unexpect point type %v, skipping ...", metricType.String())
+	}
+	return true
+}
+
+func (ma *MetricsAdjuster) adjustBuckets(current, initial []*metricspb.DistributionValue_Bucket) {
+	if len(current) != len(initial) {
+		// this shouldn't happen
+		ma.logger.Infof("len(current buckets): %v != len(initial buckets): %v", len(current), len(initial))
+	}
+	for i := 0; i < len(current); i++ {
+		current[i].Count -= initial[i].Count
+	}
+}