Add silence logging option

cmd/alertmanager/main.go

@@ -186,6 +186,7 @@ func run() int {
 		dataDir         = kingpin.Flag("storage.path", "Base path for data storage.").Default("data/").String()
 		retention       = kingpin.Flag("data.retention", "How long to keep data for.").Default("120h").Duration()
 		alertGCInterval = kingpin.Flag("alerts.gc-interval", "Interval between alert GC.").Default("30m").Duration()
+		silenceLogging  = kingpin.Flag("silences.logging", "Enable logging silences. If it is enabled, the status change of silence will be logged").Bool()
 
 		webConfig      = webflag.AddFlags(kingpin.CommandLine)
 		externalURL    = kingpin.Flag("web.external-url", "The URL under which Alertmanager is externally reachable (for example, if Alertmanager is served via a reverse proxy). Used for generating relative and absolute links back to Alertmanager itself. If the URL has a path portion, it will be used to prefix all HTTP endpoints served by Alertmanager. If omitted, relevant URL components will be derived automatically.").String()
@@ -278,6 +279,7 @@ func run() int {
 		Retention:    *retention,
 		Logger:       log.With(logger, "component", "silences"),
 		Metrics:      prometheus.DefaultRegisterer,
+		Logging:      *silenceLogging,
 	}
 
 	silences, err := silence.New(silenceOpts)

silence/silence.go

@@ -24,6 +24,7 @@ import (
 	"reflect"
 	"regexp"
 	"sort"
+	"strings"
 	"sync"
 	"time"
 
@@ -183,6 +184,7 @@ type Silences struct {
 	metrics   *metrics
 	now       func() time.Time
 	retention time.Duration
+	logging   bool
 
 	mtx       sync.RWMutex
 	st        state
@@ -289,6 +291,8 @@ type Options struct {
 	// garbage collected after the given duration after they ended.
 	Retention time.Duration
 
+	Logging bool
+
 	// A logger used by background processing.
 	Logger  log.Logger
 	Metrics prometheus.Registerer
@@ -319,6 +323,7 @@ func New(o Options) (*Silences, error) {
 		mc:        matcherCache{},
 		logger:    log.NewNopLogger(),
 		retention: o.Retention,
+		logging:   o.Logging,
 		now:       utcNow,
 		broadcast: func([]byte) {},
 		st:        state{},
@@ -530,6 +535,9 @@ func (s *Silences) Set(sil *pb.Silence) (string, error) {
 	}
 	if ok {
 		if canUpdate(prev, sil, now) {
+			if s.logging {
+				s.logginSilences("update silence", sil)
+			}
 			return sil.Id, s.setSilence(sil, now)
 		}
 		if getState(prev, s.now()) != types.SilenceStateExpired {
@@ -550,6 +558,10 @@ func (s *Silences) Set(sil *pb.Silence) (string, error) {
 		sil.StartsAt = now
 	}
 
+	if s.logging {
+		s.logginSilences("create silence", sil)
+	}
+
 	return sil.Id, s.setSilence(sil, now)
 }
 
@@ -607,6 +619,10 @@ func (s *Silences) expire(id string) error {
 		sil.EndsAt = now
 	}
 
+	if s.logging {
+		s.logginSilences("expire silence", sil)
+	}
+
 	return s.setSilence(sil, now)
 }
 
@@ -943,3 +959,30 @@ func openReplace(filename string) (*replaceFile, error) {
 	}
 	return rf, nil
 }
+
+// logging silence status changes.
+func (s *Silences) logginSilences(msg string, sil *pb.Silence) {
+	var listMatchers []string
+	var matcher_type_operator = map[string]string{
+		"EQUAL":      "=",
+		"REGEXP":     "=~",
+		"NOT_EQUAL":  "!=",
+		"NOT_REGEXP": "!~",
+	}
+	for _, matcher := range sil.Matchers {
+		ms := []string{matcher.Name, matcher_type_operator[matcher.Type.String()], matcher.Pattern}
+		m := strings.Join(ms, ``)
+		listMatchers = append(listMatchers, m)
+	}
+	strMatchers := strings.Join(listMatchers, `,`)
+
+	level.Info(s.logger).Log(
+		"msg", msg,
+		"Id", sil.Id,
+		"CreatedBy", sil.CreatedBy,
+		"Comment", sil.Comment,
+		"StartsAt", sil.StartsAt,
+		"EndsAt", sil.EndsAt,
+		"Matchers", strMatchers,
+	)
+}