mvcc: document, clean up histogram variables

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

mvcc/kvstore.go

@@ -168,7 +168,7 @@ func (s *store) Hash() (hash uint32, revision int64, err error) {
 	s.b.ForceCommit()
 	h, err := s.b.Hash(DefaultIgnores)
 
-	hashDurations.Observe(time.Since(start).Seconds())
+	hashSec.Observe(time.Since(start).Seconds())
 	return h, s.currentRev, err
 }
 
@@ -221,7 +221,7 @@ func (s *store) HashByRev(rev int64) (hash uint32, currentRev int64, compactRev
 	})
 	hash = h.Sum32()
 
-	hashRevDurations.Observe(time.Since(start).Seconds())
+	hashRevSec.Observe(time.Since(start).Seconds())
 	return hash, currentRev, compactRev, err
 }
 
@@ -274,7 +274,7 @@ func (s *store) Compact(rev int64) (<-chan struct{}, error) {
 
 	s.fifoSched.Schedule(j)
 
-	indexCompactionPauseDurations.Observe(float64(time.Since(start) / time.Millisecond))
+	indexCompactionPauseMs.Observe(float64(time.Since(start) / time.Millisecond))
 	return ch, nil
 }
 

mvcc/kvstore_compaction.go

@@ -23,7 +23,7 @@ import (
 
 func (s *store) scheduleCompaction(compactMainRev int64, keep map[revision]struct{}) bool {
 	totalStart := time.Now()
-	defer dbCompactionTotalDurations.Observe(float64(time.Since(totalStart) / time.Millisecond))
+	defer dbCompactionTotalMs.Observe(float64(time.Since(totalStart) / time.Millisecond))
 	keyCompactions := 0
 	defer func() { dbCompactionKeysCounter.Add(float64(keyCompactions)) }()
 
@@ -68,7 +68,7 @@ func (s *store) scheduleCompaction(compactMainRev int64, keep map[revision]struc
 		// update last
 		revToBytes(revision{main: rev.main, sub: rev.sub + 1}, last)
 		tx.Unlock()
-		dbCompactionPauseDurations.Observe(float64(time.Since(start) / time.Millisecond))
+		dbCompactionPauseMs.Observe(float64(time.Since(start) / time.Millisecond))
 
 		select {
 		case <-time.After(100 * time.Millisecond):

mvcc/metrics.go

@@ -101,33 +101,39 @@ var (
 			Help:      "Total number of pending events to be sent.",
 		})
 
-	indexCompactionPauseDurations = prometheus.NewHistogram(
+	indexCompactionPauseMs = prometheus.NewHistogram(
 		prometheus.HistogramOpts{
 			Namespace: "etcd_debugging",
 			Subsystem: "mvcc",
 			Name:      "index_compaction_pause_duration_milliseconds",
 			Help:      "Bucketed histogram of index compaction pause duration.",
-			// 0.5ms -> 1second
-			Buckets: prometheus.ExponentialBuckets(0.5, 2, 12),
+
+			// lowest bucket start of upper bound 0.5 ms with factor 2
+			// highest bucket start of 0.5 ms * 2^13 == 4.096 sec
+			Buckets: prometheus.ExponentialBuckets(0.5, 2, 14),
 		})
 
-	dbCompactionPauseDurations = prometheus.NewHistogram(
+	dbCompactionPauseMs = prometheus.NewHistogram(
 		prometheus.HistogramOpts{
 			Namespace: "etcd_debugging",
 			Subsystem: "mvcc",
 			Name:      "db_compaction_pause_duration_milliseconds",
 			Help:      "Bucketed histogram of db compaction pause duration.",
-			// 1ms -> 4second
+
+			// lowest bucket start of upper bound 1 ms with factor 2
+			// highest bucket start of 1 ms * 2^12 == 4.096 sec
 			Buckets: prometheus.ExponentialBuckets(1, 2, 13),
 		})
 
-	dbCompactionTotalDurations = prometheus.NewHistogram(
+	dbCompactionTotalMs = prometheus.NewHistogram(
 		prometheus.HistogramOpts{
 			Namespace: "etcd_debugging",
 			Subsystem: "mvcc",
 			Name:      "db_compaction_total_duration_milliseconds",
 			Help:      "Bucketed histogram of db compaction total duration.",
-			// 100ms -> 800second
+
+			// lowest bucket start of upper bound 100 ms with factor 2
+			// highest bucket start of 100 ms * 2^13 == 8.192 sec
 			Buckets: prometheus.ExponentialBuckets(100, 2, 14),
 		})
 
@@ -169,9 +175,9 @@ var (
 	)
 	// overridden by mvcc initialization
 	reportDbTotalSizeInUseInBytesMu sync.RWMutex
-	reportDbTotalSizeInUseInBytes   func() float64 = func() float64 { return 0 }
+	reportDbTotalSizeInUseInBytes   = func() float64 { return 0 }
 
-	hashDurations = prometheus.NewHistogram(prometheus.HistogramOpts{
+	hashSec = prometheus.NewHistogram(prometheus.HistogramOpts{
 		Namespace: "etcd",
 		Subsystem: "mvcc",
 		Name:      "hash_duration_seconds",
@@ -183,7 +189,7 @@ var (
 		Buckets: prometheus.ExponentialBuckets(.01, 2, 15),
 	})
 
-	hashRevDurations = prometheus.NewHistogram(prometheus.HistogramOpts{
+	hashRevSec = prometheus.NewHistogram(prometheus.HistogramOpts{
 		Namespace: "etcd",
 		Subsystem: "mvcc",
 		Name:      "hash_rev_duration_seconds",
@@ -207,14 +213,14 @@ func init() {
 	prometheus.MustRegister(slowWatcherGauge)
 	prometheus.MustRegister(totalEventsCounter)
 	prometheus.MustRegister(pendingEventsGauge)
-	prometheus.MustRegister(indexCompactionPauseDurations)
-	prometheus.MustRegister(dbCompactionPauseDurations)
-	prometheus.MustRegister(dbCompactionTotalDurations)
+	prometheus.MustRegister(indexCompactionPauseMs)
+	prometheus.MustRegister(dbCompactionPauseMs)
+	prometheus.MustRegister(dbCompactionTotalMs)
 	prometheus.MustRegister(dbCompactionKeysCounter)
 	prometheus.MustRegister(dbTotalSize)
 	prometheus.MustRegister(dbTotalSizeInUse)
-	prometheus.MustRegister(hashDurations)
-	prometheus.MustRegister(hashRevDurations)
+	prometheus.MustRegister(hashSec)
+	prometheus.MustRegister(hashRevSec)
 }
 
 // ReportEventReceived reports that an event is received.