From b97f4cf48c27cc085218b999a663fc8127276ff5 Mon Sep 17 00:00:00 2001
From: Brian Brazil <brian.brazil@robustperception.io>
Date: Thu, 30 Nov 2017 14:36:34 +0000
Subject: [PATCH] Add metrics for rule group interval and last duration.

---
 cmd/prometheus/main.go |  1 +
 rules/manager.go       | 41 ++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/cmd/prometheus/main.go b/cmd/prometheus/main.go
index ab3a862e2..e278f5a4b 100644
--- a/cmd/prometheus/main.go
+++ b/cmd/prometheus/main.go
@@ -241,6 +241,7 @@ func main() {
 		NotifyFunc:  sendAlerts(notifier, cfg.web.ExternalURL.String()),
 		Context:     ctx,
 		ExternalURL: cfg.web.ExternalURL,
+		Registerer:  prometheus.DefaultRegisterer,
 		Logger:      log.With(logger, "component", "rule manager"),
 	})
 
diff --git a/rules/manager.go b/rules/manager.go
index 16fb48104..c9d907032 100644
--- a/rules/manager.go
+++ b/rules/manager.go
@@ -81,6 +81,18 @@ var (
 		Name:      "rule_group_iterations_total",
 		Help:      "The total number of scheduled rule group evaluations, whether executed or missed.",
 	})
+	lastDuration = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "rule_group_last_duration_seconds"),
+		"The duration of the last rule group evaulation.",
+		[]string{"rule_group"},
+		nil,
+	)
+	groupInterval = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "rule_group_interval_seconds"),
+		"The interval of a rule group.",
+		[]string{"rule_group"},
+		nil,
+	)
 )
 
 func init() {
@@ -444,17 +456,22 @@ type ManagerOptions struct {
 	Context     context.Context
 	Appendable  Appendable
 	Logger      log.Logger
+	Registerer  prometheus.Registerer
 }
 
 // NewManager returns an implementation of Manager, ready to be started
 // by calling the Run method.
 func NewManager(o *ManagerOptions) *Manager {
-	return &Manager{
+	m := &Manager{
 		groups: map[string]*Group{},
 		opts:   o,
 		block:  make(chan struct{}),
 		logger: o.Logger,
 	}
+	if o.Registerer != nil {
+		o.Registerer.MustRegister(m)
+	}
+	return m
 }
 
 // Run starts processing of the rule manager.
@@ -627,3 +644,25 @@ func (m *Manager) AlertingRules() []*AlertingRule {
 	}
 	return alerts
 }
+
+// Implements prometheus.Collector.
+func (m *Manager) Describe(ch chan<- *prometheus.Desc) {
+	ch <- lastDuration
+	ch <- groupInterval
+}
+
+// Implements prometheus.Collector.
+func (m *Manager) Collect(ch chan<- prometheus.Metric) {
+	for _, g := range m.RuleGroups() {
+		ch <- prometheus.MustNewConstMetric(lastDuration,
+			prometheus.GaugeValue,
+			g.GetEvaluationTime().Seconds(),
+			groupKey(g.file, g.name))
+	}
+	for _, g := range m.RuleGroups() {
+		ch <- prometheus.MustNewConstMetric(groupInterval,
+			prometheus.GaugeValue,
+			g.interval.Seconds(),
+			groupKey(g.file, g.name))
+	}
+}