allow relabeling of alerts

in case of dropping don't even enqueue them

config/config.go

@@ -176,9 +176,10 @@ func (u URL) MarshalYAML() (interface{}, error) {
 
 // Config is the top-level configuration for Prometheus's config files.
 type Config struct {
-	GlobalConfig  GlobalConfig    `yaml:"global"`
+	GlobalConfig        GlobalConfig     `yaml:"global"`
-	RuleFiles     []string        `yaml:"rule_files,omitempty"`
+	AlertRelabelConfigs []*RelabelConfig `yaml:"alert_relabel_configs,omitempty"`
-	ScrapeConfigs []*ScrapeConfig `yaml:"scrape_configs,omitempty"`
+	RuleFiles           []string         `yaml:"rule_files,omitempty"`
+	ScrapeConfigs       []*ScrapeConfig  `yaml:"scrape_configs,omitempty"`
 
 	// Catches all undefined fields and must be empty after parsing.
 	XXX map[string]interface{} `yaml:",inline"`

notifier/notifier.go

@@ -30,6 +30,7 @@ import (
 	"golang.org/x/net/context/ctxhttp"
 
 	"github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/retrieval"
 )
 
 const (
@@ -69,9 +70,10 @@ type Options struct {
 	QueueCapacity    int
 	Timeout          time.Duration
 	ExternalLabels   model.LabelSet
+	RelabelConfigs   []*config.RelabelConfig
 }
 
-// New constructs a neww Notifier.
+// New constructs a new Notifier.
 func New(o *Options) *Notifier {
 	ctx, cancel := context.WithCancel(context.Background())
 
@@ -136,6 +138,7 @@ func (n *Notifier) ApplyConfig(conf *config.Config) error {
 	defer n.mtx.Unlock()
 
 	n.opts.ExternalLabels = conf.GlobalConfig.ExternalLabels
+	n.opts.RelabelConfigs = conf.AlertRelabelConfigs
 	return nil
 }
 
@@ -208,6 +211,8 @@ func (n *Notifier) Send(alerts ...*model.Alert) {
 	n.mtx.Lock()
 	defer n.mtx.Unlock()
 
+	alerts = n.relabelAlerts(alerts)
+
 	// Queue capacity should be significantly larger than a single alert
 	// batch could be.
 	if d := len(alerts) - n.opts.QueueCapacity; d > 0 {
@@ -231,6 +236,18 @@ func (n *Notifier) Send(alerts ...*model.Alert) {
 	n.setMore()
 }
 
+func (n *Notifier) relabelAlerts(alerts []*model.Alert) []*model.Alert {
+	var relabeledAlerts []*model.Alert
+	for _, alert := range alerts {
+		labels, _ := retrieval.Relabel(alert.Labels, n.opts.RelabelConfigs...)
+		if labels != nil {
+			alert.Labels = labels
+			relabeledAlerts = append(relabeledAlerts, alert)
+		}
+	}
+	return relabeledAlerts
+}
+
 // setMore signals that the alert queue has items.
 func (n *Notifier) setMore() {
 	// If we cannot send on the channel, it means the signal already exists

notifier/notifier_test.go

@@ -23,6 +23,8 @@ import (
 	"time"
 
 	"github.com/prometheus/common/model"
+
+	"github.com/prometheus/prometheus/config"
 )
 
 func TestPostURL(t *testing.T) {
@@ -185,7 +187,53 @@ func TestHandlerSendAll(t *testing.T) {
 	}
 }
 
-func TestHandlerFull(t *testing.T) {
+func TestHandlerRelabel(t *testing.T) {
+	h := New(&Options{
+		QueueCapacity: 3 * maxBatchSize,
+		RelabelConfigs: []*config.RelabelConfig{
+			&config.RelabelConfig{
+				SourceLabels: model.LabelNames{"alertname"},
+				Action:       "drop",
+				Regex:        config.MustNewRegexp("drop"),
+			},
+			&config.RelabelConfig{
+				SourceLabels: model.LabelNames{"alertname"},
+				TargetLabel:  "alertname",
+				Action:       "replace",
+				Regex:        config.MustNewRegexp("rename"),
+				Replacement:  "renamed",
+			},
+		},
+	})
+
+	// This alert should be dropped due to the configuration
+	h.Send(&model.Alert{
+		Labels: model.LabelSet{
+			"alertname": "drop",
+		},
+	})
+
+	// This alert should be replaced due to the configuration
+	h.Send(&model.Alert{
+		Labels: model.LabelSet{
+			"alertname": "rename",
+		},
+	})
+
+	expected := []*model.Alert{
+		&model.Alert{
+			Labels: model.LabelSet{
+				"alertname": "renamed",
+			},
+		},
+	}
+
+	if !alertsEqual(expected, h.queue) {
+		t.Errorf("Expected alerts %v, got %v", expected, h.queue)
+	}
+}
+
+func TestHandlerQueueing(t *testing.T) {
 	var (
 		unblock  = make(chan struct{})
 		called   = make(chan struct{})