Notify only when new firing alerts are added (#1205)

After the initial notification has been sent, AlertManager shouldn't notify the
receiver again when no new alerts have been added to the group during
group_interval.

This change also modifies the acceptance test framework to assert that no
notification has been received in a given interval.

nflog/nflogpb/set.go

@@ -21,21 +21,6 @@ func (m *Entry) IsFiringSubset(subset map[uint64]struct{}) bool {
 		set[m.FiringAlerts[i]] = struct{}{}
 	}
 
-	return isSubset(set, subset)
-}
-
-// IsResolvedSubset returns whether the given subset is a subset of the alerts
-// that were resolved at the time of the last notification.
-func (m *Entry) IsResolvedSubset(subset map[uint64]struct{}) bool {
-	set := map[uint64]struct{}{}
-	for i := range m.ResolvedAlerts {
-		set[m.ResolvedAlerts[i]] = struct{}{}
-	}
-
-	return isSubset(set, subset)
-}
-
-func isSubset(set, subset map[uint64]struct{}) bool {
 	for k := range subset {
 		_, exists := set[k]
 		if !exists {

nflog/nflogpb/set_test.go

@@ -32,34 +32,6 @@ func TestIsFiringSubset(t *testing.T) {
 	}
 }
 
-func TestIsResolvedSubset(t *testing.T) {
-	e := &Entry{
-		ResolvedAlerts: []uint64{1, 2, 3},
-	}
-
-	tests := []struct {
-		subset   map[uint64]struct{}
-		expected bool
-	}{
-		{newSubset(), true}, //empty subset
-		{newSubset(1), true},
-		{newSubset(2), true},
-		{newSubset(3), true},
-		{newSubset(1, 2), true},
-		{newSubset(1, 2), true},
-		{newSubset(1, 2, 3), true},
-		{newSubset(4), false},
-		{newSubset(1, 5), false},
-		{newSubset(1, 2, 3, 6), false},
-	}
-
-	for _, test := range tests {
-		if result := e.IsResolvedSubset(test.subset); result != test.expected {
-			t.Errorf("Expected %t, got %t for subset %v", test.expected, result, elements(test.subset))
-		}
-	}
-}
-
 func newSubset(elements ...uint64) map[uint64]struct{} {
 	subset := make(map[uint64]struct{})
 	for _, el := range elements {

notify/notify.go

@@ -481,17 +481,13 @@ func (n *DedupStage) needsUpdate(entry *nflogpb.Entry, firing, resolved map[uint
 		return true, nil
 	}
 
-	// If the current alert group and last notification contain no firing alert
-	// and the resolved alerts are different, it means that some alerts have
-	// been fired and resolved during the last group_wait interval. In this
-	// case, there is no need to notify the receiver since it doesn't know
+	// Notify about all alerts being resolved. If the current alert group and
+	// last notification contain no firing alert, it means that some alerts
+	// have been fired and resolved during the last group_wait interval. In
+	// this case, there is no need to notify the receiver since it doesn't know
 	// about them.
-	if len(firing) == 0 && len(entry.FiringAlerts) == 0 {
-		return false, nil
-	}
-
-	if !entry.IsResolvedSubset(resolved) {
-		return true, nil
+	if len(firing) == 0 {
+		return len(entry.FiringAlerts) > 0, nil
 	}
 
 	// Nothing changed, only notify if the repeat interval has passed.

notify/notify_test.go

@@ -144,6 +144,36 @@ func TestDedupStageNeedsUpdate(t *testing.T) {
 			repeat:         10 * time.Minute,
 			resolvedAlerts: alertHashSet(3, 4, 5),
 			res:            false,
+		}, {
+			entry: &nflogpb.Entry{
+				FiringAlerts:   []uint64{1, 2},
+				ResolvedAlerts: []uint64{3},
+				Timestamp:      now.Add(-11 * time.Minute),
+			},
+			repeat:         10 * time.Minute,
+			firingAlerts:   alertHashSet(1),
+			resolvedAlerts: alertHashSet(2, 3),
+			res:            true,
+		}, {
+			entry: &nflogpb.Entry{
+				FiringAlerts:   []uint64{1, 2},
+				ResolvedAlerts: []uint64{3},
+				Timestamp:      now.Add(-9 * time.Minute),
+			},
+			repeat:         10 * time.Minute,
+			firingAlerts:   alertHashSet(1),
+			resolvedAlerts: alertHashSet(2, 3),
+			res:            false,
+		}, {
+			entry: &nflogpb.Entry{
+				FiringAlerts:   []uint64{1, 2},
+				ResolvedAlerts: []uint64{3},
+				Timestamp:      now.Add(-9 * time.Minute),
+			},
+			repeat:         10 * time.Minute,
+			firingAlerts:   alertHashSet(),
+			resolvedAlerts: alertHashSet(1, 2, 3),
+			res:            true,
 		},
 	}
 	for i, c := range cases {

test/acceptance/send_test.go

@@ -387,10 +387,8 @@ receivers:
 		Alert("alertname", "test", "lbl", "v2").Active(1),
 		Alert("alertname", "test", "lbl", "v3").Active(3),
 	)
-	co1.Want(Between(12, 12.5),
-		Alert("alertname", "test", "lbl", "v2").Active(1, 11),
-		Alert("alertname", "test", "lbl", "v3").Active(3),
-	)
+	// no notification should be sent after group_interval because no new alert has been fired
+	co1.Want(Between(12, 12.5))
 
 	co2.Want(Between(2, 2.5),
 		Alert("alertname", "test", "lbl", "v1").Active(1),
@@ -400,9 +398,7 @@ receivers:
 		Alert("alertname", "test", "lbl", "v2").Active(1),
 		Alert("alertname", "test", "lbl", "v3").Active(3),
 	)
-	co2.Want(Between(12, 12.5),
-		Alert("alertname", "test", "lbl", "v3").Active(3),
-	)
+	co1.Want(Between(12, 12.5))
 
 	at.Run()
 }

test/collector.go

@@ -92,8 +92,15 @@ func (c *Collector) check() string {
 	for iv, expected := range c.expected {
 		report += fmt.Sprintf("interval %v\n", iv)
 
+		var alerts []model.Alerts
+		for at, got := range c.collected {
+			if iv.contains(at) {
+				alerts = append(alerts, got...)
+			}
+		}
+
 		for _, exp := range expected {
-			var found model.Alerts
+			found := len(exp) == 0 && len(alerts) == 0
 
 			report += fmt.Sprintf("---\n")
 
@@ -101,22 +108,14 @@ func (c *Collector) check() string {
 				report += fmt.Sprintf("- %v\n", c.opts.alertString(e))
 			}
 
-			for at, got := range c.collected {
-				if !iv.contains(at) {
-					continue
-				}
-				for _, a := range got {
+			for _, a := range alerts {
 				if batchesEqual(exp, a, c.opts) {
-						found = a
-						break
-					}
-				}
-				if found != nil {
+					found = true
 					break
 				}
 			}
 
-			if found != nil {
+			if found {
 				report += fmt.Sprintf("  [ ✓ ]\n")
 			} else {
 				c.t.Fail()