feat: configurable quantiles for Summaries

* Quantile values for a Summary are now configurable.

* The default quantiles (DefObjectives) in the prometheus Go client library is
deprecated. This commit removes the reliance on it.

Signed-off-by: Harry Bagdi <harrybagdi@gmail.com>

README.md

@@ -176,6 +176,15 @@ mappings:
     provider: "$2"
     outcome: "$3"
     job: "${1}_server"
+  quantiles:           # Optionally configure quantiles for your summaries
+    - quantile: 0.99   # https://prometheus.io/docs/practices/histograms/#quantiles
+      error: 0.001
+    - quantile: 0.95
+      error: 0.01
+    - quantile: 0.9
+      error: 0.05
+    - quantile: 0.5
+      error: 0.005
 ```
 
 Another capability when using YAML configuration is the ability to define matches

exporter.go

@@ -117,23 +117,34 @@ func (c *GaugeContainer) Get(metricName string, labels prometheus.Labels, help s
 
 type SummaryContainer struct {
 	Elements map[uint64]prometheus.Summary
+	mapper   *metricMapper
 }
 
-func NewSummaryContainer() *SummaryContainer {
+func NewSummaryContainer(mapper *metricMapper) *SummaryContainer {
 	return &SummaryContainer{
 		Elements: make(map[uint64]prometheus.Summary),
+		mapper:   mapper,
 	}
 }
 
-func (c *SummaryContainer) Get(metricName string, labels prometheus.Labels, help string) (prometheus.Summary, error) {
+func (c *SummaryContainer) Get(metricName string, labels prometheus.Labels, help string, mapping *metricMapping) (prometheus.Summary, error) {
 	hash := hashNameAndLabels(metricName, labels)
 	summary, ok := c.Elements[hash]
 	if !ok {
+		quantiles := c.mapper.Defaults.Quantiles
+		if mapping != nil && mapping.Quantiles != nil && len(mapping.Quantiles) > 0 {
+			quantiles = mapping.Quantiles
+		}
+		objectives := make(map[float64]float64)
+		for _, q := range quantiles {
+			objectives[q.Quantile] = q.Error
+		}
 		summary = prometheus.NewSummary(
 			prometheus.SummaryOpts{
 				Name:        metricName,
 				Help:        help,
 				ConstLabels: labels,
+				Objectives:  objectives,
 			})
 		if err := prometheus.Register(summary); err != nil {
 			return nil, err
@@ -350,6 +361,7 @@ func (b *Exporter) Listen(e <-chan Events) {
 						metricName,
 						prometheusLabels,
 						help,
+						mapping,
 					)
 					if err == nil {
 						summary.Observe(event.Value())
@@ -375,7 +387,7 @@ func NewExporter(mapper *metricMapper) *Exporter {
 	return &Exporter{
 		Counters:   NewCounterContainer(),
 		Gauges:     NewGaugeContainer(),
-		Summaries:  NewSummaryContainer(),
+		Summaries:  NewSummaryContainer(mapper),
 		Histograms: NewHistogramContainer(mapper),
 		mapper:     mapper,
 	}

mapper.go

@@ -36,6 +36,7 @@ var (
 type mapperConfigDefaults struct {
 	TimerType timerType         `yaml:"timer_type"`
 	Buckets   []float64         `yaml:"buckets"`
+	Quantiles []metricObjective `yaml:"quantiles"`
 	MatchType matchType         `yaml:"match_type"`
 }
 
@@ -54,12 +55,24 @@ type metricMapping struct {
 	Labels          prometheus.Labels `yaml:"labels"`
 	TimerType       timerType         `yaml:"timer_type"`
 	Buckets         []float64         `yaml:"buckets"`
+	Quantiles       []metricObjective `yaml:"quantiles"`
 	MatchType       matchType         `yaml:"match_type"`
 	HelpText        string            `yaml:"help"`
 	Action          actionType        `yaml:"action"`
 	MatchMetricType metricType        `yaml:"match_metric_type"`
 }
 
+type metricObjective struct {
+	Quantile float64 `yaml:"quantile"`
+	Error    float64 `yaml:"error"`
+}
+
+var defaultQuantiles = []metricObjective{
+	{Quantile: 0.5, Error: 0.05},
+	{Quantile: 0.9, Error: 0.01},
+	{Quantile: 0.99, Error: 0.001},
+}
+
 func (m *metricMapper) initFromYAMLString(fileContents string) error {
 	var n metricMapper
 
@@ -71,6 +84,10 @@ func (m *metricMapper) initFromYAMLString(fileContents string) error {
 		n.Defaults.Buckets = prometheus.DefBuckets
 	}
 
+	if n.Defaults.Quantiles == nil || len(n.Defaults.Quantiles) == 0 {
+		n.Defaults.Quantiles = defaultQuantiles
+	}
+
 	if n.Defaults.MatchType == matchTypeDefault {
 		n.Defaults.MatchType = matchTypeGlob
 	}
@@ -130,6 +147,10 @@ func (m *metricMapper) initFromYAMLString(fileContents string) error {
 			currentMapping.Buckets = n.Defaults.Buckets
 		}
 
+		if currentMapping.Quantiles == nil || len(currentMapping.Quantiles) == 0 {
+			currentMapping.Quantiles = n.Defaults.Quantiles
+		}
+
 	}
 
 	m.mutex.Lock()

mapper_test.go

@@ -20,6 +20,7 @@ import (
 type mappings map[string]struct {
 	name       string
 	labels     map[string]string
+	quantiles  []metricObjective
 	notPresent bool
 }
 
@@ -287,11 +288,40 @@ mappings:
   timer_type: summary
   name: "foo"
   labels: {}
+  quantiles:
+    - quantile: 0.42
+      error: 0.04
+    - quantile: 0.7
+      error: 0.002
   `,
 			mappings: mappings{
 				"test.*.*": {
 					name:   "foo",
 					labels: map[string]string{},
+					quantiles: []metricObjective{
+						{Quantile: 0.42, Error: 0.04},
+						{Quantile: 0.7, Error: 0.002},
+					},
+				},
+			},
+		},
+		{
+			config: `---
+mappings:
+- match: test1.*.*
+  timer_type: summary
+  name: "foo"
+  labels: {}
+  `,
+			mappings: mappings{
+				"test1.*.*": {
+					name:   "foo",
+					labels: map[string]string{},
+					quantiles: []metricObjective{
+						{Quantile: 0.5, Error: 0.05},
+						{Quantile: 0.9, Error: 0.01},
+						{Quantile: 0.99, Error: 0.001},
+					},
 				},
 			},
 		},
@@ -471,6 +501,19 @@ mappings:
 				}
 			}
 
+			if len(mapping.quantiles) != 0 {
+				if len(mapping.quantiles) != len(m.Quantiles) {
+					t.Fatalf("%d.%q: Expected %d quantiles, got %d", i, metric, len(mapping.quantiles), len(m.Quantiles))
+				}
+				for i, quantile := range mapping.quantiles {
+					if quantile.Quantile != m.Quantiles[i].Quantile {
+						t.Fatalf("%d.%q: Expected quantile %v, got %v", i, metric, m.Quantiles[i].Quantile, quantile.Quantile)
+					}
+					if quantile.Error != m.Quantiles[i].Error {
+						t.Fatalf("%d.%q: Expected Error margin %v, got %v", i, metric, m.Quantiles[i].Error, quantile.Error)
+					}
+				}
+			}
 		}
 	}
 }