Do not double-count non-persisted head chunks on loading.

storage/local/persistence.go

@@ -22,7 +22,6 @@ import (
 	"path"
 	"path/filepath"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/golang/glog"
@@ -586,7 +585,7 @@ func (p *persistence) checkpointSeriesMapAndHeads(fingerprintToSeries *seriesMap
 // this method during start-up while nothing else is running in storage
 // land. This method is utterly goroutine-unsafe.
 func (p *persistence) loadSeriesMapAndHeads() (sm *seriesMap, err error) {
-	var chunksTotal, chunkDescsTotal int64
+	var chunkDescsTotal int64
 	fingerprintToSeries := make(map[clientmodel.Fingerprint]*memorySeries)
 	sm = &seriesMap{m: fingerprintToSeries}
 
@@ -599,7 +598,6 @@ func (p *persistence) loadSeriesMapAndHeads() (sm *seriesMap, err error) {
 			}
 		}
 		if err == nil {
-			atomic.AddInt64(&numMemChunks, chunksTotal)
 			numMemChunkDescs.Add(float64(chunkDescsTotal))
 		}
 	}()
@@ -704,7 +702,6 @@ func (p *persistence) loadSeriesMapAndHeads() (sm *seriesMap, err error) {
 				}
 			} else {
 				// Non-persisted head chunk.
-				chunksTotal++
 				chunkType, err := r.ReadByte()
 				if err != nil {
 					glog.Warning("Could not decode chunk type:", err)
@@ -718,6 +715,7 @@ func (p *persistence) loadSeriesMapAndHeads() (sm *seriesMap, err error) {
 					return sm, nil
 				}
 				chunkDescs[i] = newChunkDesc(chunk)
+				chunkDescsTotal-- // Avoid double-counting by newChunkDesc.
 			}
 		}
 

storage/local/storage.go

@@ -1027,8 +1027,10 @@ func (s *memorySeriesStorage) Collect(ch chan<- prometheus.Metric) {
 	ch <- s.ingestedSamplesCount
 	ch <- s.invalidPreloadRequestsCount
 
-	count := atomic.LoadInt64(&numMemChunks)
-	ch <- prometheus.MustNewConstMetric(numMemChunksDesc, prometheus.GaugeValue, float64(count))
+	ch <- prometheus.MustNewConstMetric(
+		numMemChunksDesc,
+		prometheus.GaugeValue,
+		float64(atomic.LoadInt64(&numMemChunks)))
 }
 
 // chunkMaps is a slice of maps with chunkDescs to be persisted.