Very basic staleness handling for rules.

rules/manager.go

@@ -16,6 +16,7 @@ package rules
 import (
 	"fmt"
 	"io/ioutil"
+	"math"
 	"net/url"
 	"path/filepath"
 	"sync"
@@ -30,6 +31,9 @@ import (
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/notifier"
+	"github.com/prometheus/prometheus/pkg/labels"
+	"github.com/prometheus/prometheus/pkg/timestamp"
+	"github.com/prometheus/prometheus/pkg/value"
 	"github.com/prometheus/prometheus/promql"
 	"github.com/prometheus/prometheus/storage"
 	"github.com/prometheus/prometheus/util/strutil"
@@ -122,10 +126,11 @@ type Rule interface {
 
 // Group is a set of rules that have a logical relation.
 type Group struct {
-	name     string
-	interval time.Duration
-	rules    []Rule
-	opts     *ManagerOptions
+	name                 string
+	interval             time.Duration
+	rules                []Rule
+	opts                 *ManagerOptions
+	seriesInPreviousEval map[string]labels.Labels
 
 	done       chan struct{}
 	terminated chan struct{}
@@ -134,12 +139,13 @@ type Group struct {
 // NewGroup makes a new Group with the given name, options, and rules.
 func NewGroup(name string, interval time.Duration, rules []Rule, opts *ManagerOptions) *Group {
 	return &Group{
-		name:       name,
-		interval:   interval,
-		rules:      rules,
-		opts:       opts,
-		done:       make(chan struct{}),
-		terminated: make(chan struct{}),
+		name:                 name,
+		interval:             interval,
+		rules:                rules,
+		opts:                 opts,
+		seriesInPreviousEval: map[string]labels.Labels{},
+		done:                 make(chan struct{}),
+		terminated:           make(chan struct{}),
 	}
 }
 
@@ -214,8 +220,9 @@ func (g *Group) offset() time.Duration {
 	return time.Duration(next - now)
 }
 
-// copyState copies the alerting rule state from the given group.
+// copyState copies the alerting rule and staleness related state from the given group.
 func (g *Group) copyState(from *Group) {
+	g.seriesInPreviousEval = from.seriesInPreviousEval
 	for _, fromRule := range from.rules {
 		far, ok := fromRule.(*AlertingRule)
 		if !ok {
@@ -252,8 +259,10 @@ func typeForRule(r Rule) ruleType {
 // rule dependency.
 func (g *Group) Eval() {
 	var (
-		now = time.Now()
-		wg  sync.WaitGroup
+		now            = time.Now()
+		wg             sync.WaitGroup
+		mu             sync.Mutex
+		seriesReturned = make(map[string]labels.Labels, len(g.seriesInPreviousEval))
 	)
 
 	for _, rule := range g.rules {
@@ -307,6 +316,10 @@ func (g *Group) Eval() {
 					default:
 						log.With("sample", s).With("err", err).Warn("Rule evaluation result discarded")
 					}
+				} else {
+					mu.Lock()
+					seriesReturned[s.Metric.String()] = s.Metric
+					mu.Unlock()
 				}
 			}
 			if numOutOfOrder > 0 {
@@ -321,6 +334,35 @@ func (g *Group) Eval() {
 		}(rule)
 	}
 	wg.Wait()
+
+	// TODO(bbrazil): This should apply per-rule.
+	app, err := g.opts.Appendable.Appender()
+	if err != nil {
+		log.With("err", err).Warn("creating appender failed")
+		return
+	}
+	for metric, lset := range g.seriesInPreviousEval {
+		if _, ok := seriesReturned[metric]; !ok {
+			// Series no longer exposed, mark it stale.
+			_, err = app.Add(lset, timestamp.FromTime(now), math.Float64frombits(value.StaleNaN))
+			switch err {
+			case nil:
+			case storage.ErrOutOfOrderSample, storage.ErrDuplicateSampleForTimestamp:
+				// Do not count these in logging, as this is expected if series
+				// is exposed from a different group.
+				continue
+			default:
+				log.With("sample", metric).With("err", err).Warn("adding stale sample failed")
+				if err := app.Rollback(); err != nil {
+					log.With("err", err).Warn("rule stale sample rollback failed")
+				}
+			}
+		}
+	}
+	if err := app.Commit(); err != nil {
+		log.With("err", err).Warn("rule stale sample appending failed")
+	}
+	g.seriesInPreviousEval = seriesReturned
 }
 
 // sendAlerts sends alert notifications for the given rule.
@@ -433,7 +475,7 @@ func (m *Manager) ApplyConfig(conf *config.Config) error {
 		wg.Add(1)
 
 		// If there is an old group with the same identifier, stop it and wait for
-		// it to finish the current iteration. Then copy its into the new group.
+		// it to finish the current iteration. Then copy it into the new group.
 		oldg, ok := m.groups[newg.name]
 		delete(m.groups, newg.name)