Expose rules.NewGroupMetrics and rules.Metrics. (#5059)

Signed-off-by: Tom Wilkie <tom.wilkie@gmail.com>

rules/manager.go

@@ -61,7 +61,8 @@ var (
 	)
 )
 
-type metrics struct {
+// Metrics for rule evaluation.
+type Metrics struct {
 	evalDuration        prometheus.Summary
 	evalFailures        prometheus.Counter
 	evalTotal           prometheus.Counter
@@ -72,8 +73,10 @@ type metrics struct {
 	groupLastDuration   *prometheus.GaugeVec
 }
 
-func newGroupMetrics(reg prometheus.Registerer) *metrics {
+// NewGroupMetrics makes a new Metrics and registers them with then provided registerer,
-	m := &metrics{
+// if not nil.
+func NewGroupMetrics(reg prometheus.Registerer) *Metrics {
+	m := &Metrics{
 		evalDuration: prometheus.NewSummary(
 			prometheus.SummaryOpts{
 				Namespace: namespace,
@@ -220,14 +223,14 @@ type Group struct {
 
 	logger log.Logger
 
-	metrics *metrics
+	metrics *Metrics
 }
 
 // NewGroup makes a new Group with the given name, options, and rules.
 func NewGroup(name, file string, interval time.Duration, rules []Rule, shouldRestore bool, opts *ManagerOptions) *Group {
-	metrics := opts.metrics
+	metrics := opts.Metrics
 	if metrics == nil {
-		metrics = newGroupMetrics(opts.Registerer)
+		metrics = NewGroupMetrics(opts.Registerer)
 	}
 
 	metrics.groupLastEvalTime.WithLabelValues(groupKey(file, name))
@@ -684,14 +687,14 @@ type ManagerOptions struct {
 	ForGracePeriod  time.Duration
 	ResendDelay     time.Duration
 
-	metrics *metrics
+	Metrics *Metrics
 }
 
 // NewManager returns an implementation of Manager, ready to be started
 // by calling the Run method.
 func NewManager(o *ManagerOptions) *Manager {
-	if o.metrics == nil {
+	if o.Metrics == nil {
-		o.metrics = newGroupMetrics(o.Registerer)
+		o.Metrics = NewGroupMetrics(o.Registerer)
 	}
 
 	m := &Manager{
@@ -705,7 +708,7 @@ func NewManager(o *ManagerOptions) *Manager {
 		o.Registerer.MustRegister(m)
 	}
 
-	o.metrics.iterationsMissed.Inc()
+	o.Metrics.iterationsMissed.Inc()
 	return m
 }