lib/storage: adds metrics for downsampling (#382)

* lib/storage: adds metrics for downsampling
vm_downsampling_partitions_scheduled - shows the number of parts, that must be downsampled
vm_downsampling_partitions_scheduled_size_bytes - shows total size in bytes for parts, the must be donwsampled

These two metrics answer the questions - is downsampling running? how many parts scheduled for downsampling and how many of them currently downsampled? Storage space that it occupies.

https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2612

* wip

Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>

app/vmstorage/main.go

@@ -626,6 +626,9 @@ func writeStorageMetrics(w io.Writer, strg *storage.Storage) {
 	metrics.WriteCounterUint64(w, `vm_cache_collisions_total{type="storage/metricName"}`, m.MetricNameCacheCollisions)
 
 	metrics.WriteGaugeUint64(w, `vm_next_retention_seconds`, m.NextRetentionSeconds)
+
+	metrics.WriteGaugeUint64(w, `vm_downsampling_partitions_scheduled`, tm.ScheduledDownsamplingPartitions)
+	metrics.WriteGaugeUint64(w, `vm_downsampling_partitions_scheduled_size_bytes`, tm.ScheduledDownsamplingPartitionsSize)
 }
 
 func jsonResponseError(w http.ResponseWriter, err error) {

lib/storage/partition.go

@@ -91,6 +91,8 @@ type partition struct {
 	smallRowsDeleted    atomic.Uint64
 	bigRowsDeleted      atomic.Uint64
 
+	isDedupScheduled atomic.Bool
+
 	mergeIdx atomic.Uint64
 
 	// the path to directory with smallParts.
@@ -326,6 +328,9 @@ type partitionMetrics struct {
 	InmemoryPartsRefCount uint64
 	SmallPartsRefCount    uint64
 	BigPartsRefCount      uint64
+
+	ScheduledDownsamplingPartitions     uint64
+	ScheduledDownsamplingPartitionsSize uint64
 }
 
 // TotalRowsCount returns total number of rows in tm.
@@ -339,12 +344,20 @@ func (pt *partition) UpdateMetrics(m *partitionMetrics) {
 
 	pt.partsLock.Lock()
 
+	isDedupScheduled := pt.isDedupScheduled.Load()
+	if isDedupScheduled {
+		m.ScheduledDownsamplingPartitions++
+	}
+
 	for _, pw := range pt.inmemoryParts {
 		p := pw.p
 		m.InmemoryRowsCount += p.ph.RowsCount
 		m.InmemoryBlocksCount += p.ph.BlocksCount
 		m.InmemorySizeBytes += p.size
 		m.InmemoryPartsRefCount += uint64(pw.refCount.Load())
+		if isDedupScheduled {
+			m.ScheduledDownsamplingPartitionsSize += p.size
+		}
 	}
 	for _, pw := range pt.smallParts {
 		p := pw.p
@@ -352,6 +365,9 @@ func (pt *partition) UpdateMetrics(m *partitionMetrics) {
 		m.SmallBlocksCount += p.ph.BlocksCount
 		m.SmallSizeBytes += p.size
 		m.SmallPartsRefCount += uint64(pw.refCount.Load())
+		if isDedupScheduled {
+			m.ScheduledDownsamplingPartitionsSize += p.size
+		}
 	}
 	for _, pw := range pt.bigParts {
 		p := pw.p
@@ -359,6 +375,9 @@ func (pt *partition) UpdateMetrics(m *partitionMetrics) {
 		m.BigBlocksCount += p.ph.BlocksCount
 		m.BigSizeBytes += p.size
 		m.BigPartsRefCount += uint64(pw.refCount.Load())
+		if isDedupScheduled {
+			m.ScheduledDownsamplingPartitionsSize += p.size
+		}
 	}
 
 	m.InmemoryPartsCount += uint64(len(pt.inmemoryParts))

lib/storage/table.go

@@ -442,15 +442,21 @@ func (tb *table) finalDedupWatcher() {
 		defer tb.PutPartitions(ptws)
 		timestamp := timestampFromTime(time.Now())
 		currentPartitionName := timestampToPartitionName(timestamp)
+		var ptwsToDedup []*partitionWrapper
 		for _, ptw := range ptws {
 			if ptw.pt.name == currentPartitionName || !ptw.pt.isFinalDedupNeeded() {
 				// Do not run final dedup for the current month.
 				continue
 			}
+			// mark partition with final deduplication marker
+			ptw.pt.isDedupScheduled.Store(true)
+			ptwsToDedup = append(ptwsToDedup, ptw)
+		}
+		for _, ptw := range ptwsToDedup {
 			if err := ptw.pt.runFinalDedup(); err != nil {
 				logger.Errorf("cannot run final dedup for partition %s: %s", ptw.pt.name, err)
-				continue
 			}
+			ptw.pt.isDedupScheduled.Store(false)
 		}
 	}
 	d := timeutil.AddJitterToDuration(time.Hour)