Add various persistence related metrics (#2333)

Add metrics around checkpointing and persistence

* Add a metric to say if checkpointing is happening,
and another to track total checkpoint time and count.

This breaks the existing prometheus_local_storage_checkpoint_duration_seconds
by renaming it to prometheus_local_storage_checkpoint_last_duration_seconds
as the former name is more appropriate for a summary.

* Add metric for last checkpoint size.

* Add metric for series/chunks processed by checkpoints.

For long checkpoints it'd be useful to see how they're progressing.

* Add metric for dirty series

* Add metric for number of chunks persisted per series.

You can get the number of chunks from chunk_ops,
but not the matching number of series. This helps determine
the size of the writes being made.

* Add metric for chunks queued for persistence

Chunks created includes both chunks that'll need persistence
and chunks read in for queries. This only includes chunks created
for persistence.

* Code review comments on new persistence metrics.

consoles/prometheus-overview.html

@@ -46,7 +46,7 @@
   </tr>
   <tr>
     <td>Checkpoint Duration</td>
-    <td>{{ template "prom_query_drilldown" (args (printf "prometheus_local_storage_checkpoint_duration_seconds{job='prometheus',instance='%s'}" .Params.instance) "" "humanizeDuration") }}</td>
+    <td>{{ template "prom_query_drilldown" (args (printf "prometheus_local_storage_checkpoint_last_duration_seconds{job='prometheus',instance='%s'}" .Params.instance) "" "humanizeDuration") }}</td>
   </tr>
 
   <tr>

storage/local/persistence.go

@@ -114,9 +114,14 @@ type persistence struct {
 	indexingQueueCapacity   prometheus.Metric
 	indexingBatchSizes      prometheus.Summary
 	indexingBatchDuration   prometheus.Summary
-	checkpointDuration    prometheus.Gauge
+	checkpointDuration      prometheus.Summary
+	checkpointLastDuration  prometheus.Gauge
+	checkpointLastSize      prometheus.Gauge
+	checkpointChunksWritten prometheus.Summary
 	dirtyCounter            prometheus.Counter
 	startedDirty            prometheus.Gauge
+	checkpointing           prometheus.Gauge
+	seriesChunksPersisted   prometheus.Histogram
 
 	dirtyMtx       sync.Mutex     // Protects dirty and becameDirty.
 	dirty          bool           // true if persistence was started in dirty state.
@@ -247,11 +252,31 @@ func newPersistence(
 				Help:      "Quantiles for batch indexing duration in seconds.",
 			},
 		),
-		checkpointDuration: prometheus.NewGauge(prometheus.GaugeOpts{
+		checkpointLastDuration: prometheus.NewGauge(prometheus.GaugeOpts{
 			Namespace: namespace,
 			Subsystem: subsystem,
+			Name:      "checkpoint_last_duration_seconds",
+			Help:      "The duration in seconds it took to last checkpoint open chunks and chunks yet to be persisted.",
+		}),
+		checkpointDuration: prometheus.NewSummary(prometheus.SummaryOpts{
+			Namespace:  namespace,
+			Subsystem:  subsystem,
+			Objectives: map[float64]float64{},
 			Name:       "checkpoint_duration_seconds",
-			Help:      "The duration in seconds it took to checkpoint in-memory metrics and head chunks.",
+			Help:       "The duration in seconds taken for checkpointing open chunks and chunks yet to be persisted",
+		}),
+		checkpointLastSize: prometheus.NewGauge(prometheus.GaugeOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "checkpoint_last_size_bytes",
+			Help:      "The size of the last checkpoint of open chunks and chunks yet to be persisted",
+		}),
+		checkpointChunksWritten: prometheus.NewSummary(prometheus.SummaryOpts{
+			Namespace:  namespace,
+			Subsystem:  subsystem,
+			Objectives: map[float64]float64{},
+			Name:       "checkpoint_series_chunks_written",
+			Help:       "The number of chunk written per series while checkpointing open chunks and chunks yet to be persisted.",
 		}),
 		dirtyCounter: prometheus.NewCounter(prometheus.CounterOpts{
 			Namespace: namespace,
@@ -265,6 +290,21 @@ func newPersistence(
 			Name:      "started_dirty",
 			Help:      "Whether the local storage was found to be dirty (and crash recovery occurred) during Prometheus startup.",
 		}),
+		checkpointing: prometheus.NewGauge(prometheus.GaugeOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "checkpointing",
+			Help:      "1 if the storage is checkpointing, 0 otherwise.",
+		}),
+		seriesChunksPersisted: prometheus.NewHistogram(prometheus.HistogramOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "series_chunks_persisted",
+			Help:      "The number of chunks persisted per series.",
+			// Even with 4 bytes per sample, you're not going to get more than 85
+			// chunks in 6 hours for a time series with 1s resolution.
+			Buckets: []float64{1, 2, 4, 8, 16, 32, 64, 128},
+		}),
 		dirty:          dirty,
 		pedanticChecks: pedanticChecks,
 		dirtyFileName:  dirtyPath,
@@ -310,8 +350,13 @@ func (p *persistence) Describe(ch chan<- *prometheus.Desc) {
 	p.indexingBatchSizes.Describe(ch)
 	p.indexingBatchDuration.Describe(ch)
 	ch <- p.checkpointDuration.Desc()
+	ch <- p.checkpointLastDuration.Desc()
+	ch <- p.checkpointLastSize.Desc()
+	ch <- p.checkpointChunksWritten.Desc()
+	ch <- p.checkpointing.Desc()
 	ch <- p.dirtyCounter.Desc()
 	ch <- p.startedDirty.Desc()
+	ch <- p.seriesChunksPersisted.Desc()
 }
 
 // Collect implements prometheus.Collector.
@@ -323,8 +368,13 @@ func (p *persistence) Collect(ch chan<- prometheus.Metric) {
 	p.indexingBatchSizes.Collect(ch)
 	p.indexingBatchDuration.Collect(ch)
 	ch <- p.checkpointDuration
+	ch <- p.checkpointLastDuration
+	ch <- p.checkpointLastSize
+	ch <- p.checkpointChunksWritten
+	ch <- p.checkpointing
 	ch <- p.dirtyCounter
 	ch <- p.startedDirty
+	ch <- p.seriesChunksPersisted
 }
 
 // isDirty returns the dirty flag in a goroutine-safe way.
@@ -559,6 +609,8 @@ func (p *persistence) loadChunkDescs(fp model.Fingerprint, offsetFromEnd int) ([
 //
 func (p *persistence) checkpointSeriesMapAndHeads(fingerprintToSeries *seriesMap, fpLocker *fingerprintLocker) (err error) {
 	log.Info("Checkpointing in-memory metrics and chunks...")
+	p.checkpointing.Set(1)
+	defer p.checkpointing.Set(0)
 	begin := time.Now()
 	f, err := os.OpenFile(p.headsTempFileName(), os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0640)
 	if err != nil {
@@ -581,7 +633,8 @@ func (p *persistence) checkpointSeriesMapAndHeads(fingerprintToSeries *seriesMap
 		}
 		err = os.Rename(p.headsTempFileName(), p.headsFileName())
 		duration := time.Since(begin)
-		p.checkpointDuration.Set(duration.Seconds())
+		p.checkpointDuration.Observe(duration.Seconds())
+		p.checkpointLastDuration.Set(duration.Seconds())
 		log.Infof("Done checkpointing in-memory metrics and chunks in %v.", duration)
 	}()
 
@@ -677,6 +730,7 @@ func (p *persistence) checkpointSeriesMapAndHeads(fingerprintToSeries *seriesMap
 						return
 					}
 				}
+				p.checkpointChunksWritten.Observe(float64(len(m.series.chunkDescs) - m.series.persistWatermark))
 			}
 			// Series is checkpointed now, so declare it clean. In case the entire
 			// checkpoint fails later on, this is fine, as the storage's series
@@ -704,6 +758,11 @@ func (p *persistence) checkpointSeriesMapAndHeads(fingerprintToSeries *seriesMap
 			return err
 		}
 	}
+	info, err := f.Stat()
+	if err != nil {
+		return err
+	}
+	p.checkpointLastSize.Set(float64(info.Size()))
 	return err
 }
 
@@ -1520,6 +1579,7 @@ func (p *persistence) writeChunks(w io.Writer, chunks []chunk.Chunk) error {
 		// would only put back the original buf.
 		p.bufPool.Put(b)
 	}()
+	numChunks := len(chunks)
 
 	for batchSize := chunkMaxBatchSize; len(chunks) > 0; chunks = chunks[batchSize:] {
 		if batchSize > len(chunks) {
@@ -1543,6 +1603,7 @@ func (p *persistence) writeChunks(w io.Writer, chunks []chunk.Chunk) error {
 			return err
 		}
 	}
+	p.seriesChunksPersisted.Observe(float64(numChunks))
 	return nil
 }
 

storage/local/storage.go

@@ -178,7 +178,9 @@ type MemorySeriesStorage struct {
 	quarantineStopping, quarantineStopped chan struct{}
 
 	persistErrors                 prometheus.Counter
+	queuedChunksToPersist         prometheus.Counter
 	numSeries                     prometheus.Gauge
+	dirtySeries                   prometheus.Gauge
 	seriesOps                     *prometheus.CounterVec
 	ingestedSamplesCount          prometheus.Counter
 	discardedSamplesCount         *prometheus.CounterVec
@@ -240,12 +242,24 @@ func NewMemorySeriesStorage(o *MemorySeriesStorageOptions) *MemorySeriesStorage
 			Name:      "persist_errors_total",
 			Help:      "The total number of errors while persisting chunks.",
 		}),
+		queuedChunksToPersist: prometheus.NewCounter(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "queued_chunks_to_persist_total",
+			Help:      "The total number of chunks queued for persistence.",
+		}),
 		numSeries: prometheus.NewGauge(prometheus.GaugeOpts{
 			Namespace: namespace,
 			Subsystem: subsystem,
 			Name:      "memory_series",
 			Help:      "The current number of series in memory.",
 		}),
+		dirtySeries: prometheus.NewGauge(prometheus.GaugeOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "memory_dirty_series",
+			Help:      "The current number of series that would require a disk seek during crash recovery.",
+		}),
 		seriesOps: prometheus.NewCounterVec(
 			prometheus.CounterOpts{
 				Namespace: namespace,
@@ -1260,6 +1274,7 @@ loop:
 				log.Errorln("Error while checkpointing:", err)
 			} else {
 				dirtySeriesCount = 0
+				s.dirtySeries.Set(0)
 			}
 			// If a checkpoint takes longer than checkpointInterval, unluckily timed
 			// combination with the Reset(0) call below can lead to a case where a
@@ -1272,6 +1287,7 @@ loop:
 		case fp := <-memoryFingerprints:
 			if s.maintainMemorySeries(fp, model.Now().Add(-s.dropAfter)) {
 				dirtySeriesCount++
+				s.dirtySeries.Inc()
 				// Check if we have enough "dirty" series so that we need an early checkpoint.
 				// However, if we are already behind persisting chunks, creating a checkpoint
 				// would be counterproductive, as it would slow down chunk persisting even more,
@@ -1531,6 +1547,9 @@ func (s *MemorySeriesStorage) getNumChunksToPersist() int {
 // negative 'by' to decrement.
 func (s *MemorySeriesStorage) incNumChunksToPersist(by int) {
 	atomic.AddInt64(&s.numChunksToPersist, int64(by))
+	if by > 0 {
+		s.queuedChunksToPersist.Add(float64(by))
+	}
 }
 
 // calculatePersistenceUrgencyScore calculates and returns an urgency score for
@@ -1734,9 +1753,11 @@ func (s *MemorySeriesStorage) Describe(ch chan<- *prometheus.Desc) {
 	s.mapper.Describe(ch)
 
 	ch <- s.persistErrors.Desc()
+	ch <- s.queuedChunksToPersist.Desc()
 	ch <- maxChunksToPersistDesc
 	ch <- numChunksToPersistDesc
 	ch <- s.numSeries.Desc()
+	ch <- s.dirtySeries.Desc()
 	s.seriesOps.Describe(ch)
 	ch <- s.ingestedSamplesCount.Desc()
 	s.discardedSamplesCount.Describe(ch)
@@ -1753,6 +1774,7 @@ func (s *MemorySeriesStorage) Collect(ch chan<- prometheus.Metric) {
 	s.mapper.Collect(ch)
 
 	ch <- s.persistErrors
+	ch <- s.queuedChunksToPersist
 	ch <- prometheus.MustNewConstMetric(
 		maxChunksToPersistDesc,
 		prometheus.GaugeValue,
@@ -1764,6 +1786,7 @@ func (s *MemorySeriesStorage) Collect(ch chan<- prometheus.Metric) {
 		float64(s.getNumChunksToPersist()),
 	)
 	ch <- s.numSeries
+	ch <- s.dirtySeries
 	s.seriesOps.Collect(ch)
 	ch <- s.ingestedSamplesCount
 	s.discardedSamplesCount.Collect(ch)