mvcc: add store revision metrics

Add experimental metrics etcd_debugging_mvcc_current_revision and
etcd_debugging_mvcc_compact_revision.

mvcc/kvstore.go

@@ -309,14 +309,7 @@ func (s *store) Restore(b backend.Backend) error {
 }
 
 func (s *store) restore() error {
-	b := s.b
-
-	reportDbTotalSizeInBytesMu.Lock()
-	reportDbTotalSizeInBytes = func() float64 { return float64(b.Size()) }
-	reportDbTotalSizeInBytesMu.Unlock()
-	reportDbTotalSizeInUseInBytesMu.Lock()
-	reportDbTotalSizeInUseInBytes = func() float64 { return float64(b.SizeInUse()) }
-	reportDbTotalSizeInUseInBytesMu.Unlock()
+	s.setupMetricsReporter()
 
 	min, max := newRevBytes(), newRevBytes()
 	revToBytes(revision{main: 1}, min)
@@ -496,6 +489,30 @@ func (s *store) ConsistentIndex() uint64 {
 	return v
 }
 
+func (s *store) setupMetricsReporter() {
+	b := s.b
+	reportDbTotalSizeInBytesMu.Lock()
+	reportDbTotalSizeInBytes = func() float64 { return float64(b.Size()) }
+	reportDbTotalSizeInBytesMu.Unlock()
+	reportDbTotalSizeInUseInBytesMu.Lock()
+	reportDbTotalSizeInUseInBytes = func() float64 { return float64(b.SizeInUse()) }
+	reportDbTotalSizeInUseInBytesMu.Unlock()
+	reportCurrentRevMu.Lock()
+	reportCurrentRev = func() float64 {
+		s.revMu.RLock()
+		defer s.revMu.RUnlock()
+		return float64(s.currentRev)
+	}
+	reportCurrentRevMu.Unlock()
+	reportCompactRevMu.Lock()
+	reportCompactRev = func() float64 {
+		s.revMu.RLock()
+		defer s.revMu.RUnlock()
+		return float64(s.compactMainRev)
+	}
+	reportCompactRevMu.Unlock()
+}
+
 // appendMarkTombstone appends tombstone mark to normal revision bytes.
 func appendMarkTombstone(b []byte) []byte {
 	if len(b) != revBytesLen {

mvcc/metrics.go

@@ -206,6 +206,38 @@ var (
 		// highest bucket start of 0.01 sec * 2^14 == 163.84 sec
 		Buckets: prometheus.ExponentialBuckets(.01, 2, 15),
 	})
+
+	currentRev = prometheus.NewGaugeFunc(prometheus.GaugeOpts{
+		Namespace: "etcd_debugging",
+		Subsystem: "mvcc",
+		Name:      "current_revision",
+		Help:      "The current revision of store.",
+	},
+		func() float64 {
+			reportCurrentRevMu.RLock()
+			defer reportCurrentRevMu.RUnlock()
+			return reportCurrentRev()
+		},
+	)
+	// overridden by mvcc initialization
+	reportCurrentRevMu sync.RWMutex
+	reportCurrentRev   = func() float64 { return 0 }
+
+	compactRev = prometheus.NewGaugeFunc(prometheus.GaugeOpts{
+		Namespace: "etcd_debugging",
+		Subsystem: "mvcc",
+		Name:      "compact_revision",
+		Help:      "The revision of the last compaction in store.",
+	},
+		func() float64 {
+			reportCompactRevMu.RLock()
+			defer reportCompactRevMu.RUnlock()
+			return reportCompactRev()
+		},
+	)
+	// overridden by mvcc initialization
+	reportCompactRevMu sync.RWMutex
+	reportCompactRev   = func() float64 { return 0 }
 )
 
 func init() {
@@ -228,6 +260,8 @@ func init() {
 	prometheus.MustRegister(dbTotalSizeInUse)
 	prometheus.MustRegister(hashDurations)
 	prometheus.MustRegister(hashRevDurations)
+	prometheus.MustRegister(currentRev)
+	prometheus.MustRegister(compactRev)
 }
 
 // ReportEventReceived reports that an event is received.