Merge pull request prometheus#14328 from bboreham/more-dedupelabels

TSDB and scraping: improvements to dedupelabels

scrape/metrics.go

@@ -34,6 +34,7 @@ type scrapeMetrics struct {
 	targetScrapePoolExceededTargetLimit prometheus.Counter
 	targetScrapePoolTargetLimit         *prometheus.GaugeVec
 	targetScrapePoolTargetsAdded        *prometheus.GaugeVec
+	targetScrapePoolSymbolTableItems    *prometheus.GaugeVec
 	targetSyncIntervalLength            *prometheus.SummaryVec
 	targetSyncFailed                    *prometheus.CounterVec
 
@@ -129,6 +130,13 @@ func newScrapeMetrics(reg prometheus.Registerer) (*scrapeMetrics, error) {
 		},
 		[]string{"scrape_job"},
 	)
+	sm.targetScrapePoolSymbolTableItems = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "prometheus_target_scrape_pool_symboltable_items",
+			Help: "Current number of symbols in table for this scrape pool.",
+		},
+		[]string{"scrape_job"},
+	)
 	sm.targetScrapePoolSyncsCounter = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Name: "prometheus_target_scrape_pool_sync_total",
@@ -234,6 +242,7 @@ func newScrapeMetrics(reg prometheus.Registerer) (*scrapeMetrics, error) {
 		sm.targetScrapePoolExceededTargetLimit,
 		sm.targetScrapePoolTargetLimit,
 		sm.targetScrapePoolTargetsAdded,
+		sm.targetScrapePoolSymbolTableItems,
 		sm.targetSyncFailed,
 		// Used by targetScraper.
 		sm.targetScrapeExceededBodySizeLimit,
@@ -274,6 +283,7 @@ func (sm *scrapeMetrics) Unregister() {
 	sm.reg.Unregister(sm.targetScrapePoolExceededTargetLimit)
 	sm.reg.Unregister(sm.targetScrapePoolTargetLimit)
 	sm.reg.Unregister(sm.targetScrapePoolTargetsAdded)
+	sm.reg.Unregister(sm.targetScrapePoolSymbolTableItems)
 	sm.reg.Unregister(sm.targetSyncFailed)
 	sm.reg.Unregister(sm.targetScrapeExceededBodySizeLimit)
 	sm.reg.Unregister(sm.targetScrapeCacheFlushForced)

scrape/scrape.go

@@ -246,6 +246,7 @@ func (sp *scrapePool) stop() {
 		sp.metrics.targetScrapePoolSyncsCounter.DeleteLabelValues(sp.config.JobName)
 		sp.metrics.targetScrapePoolTargetLimit.DeleteLabelValues(sp.config.JobName)
 		sp.metrics.targetScrapePoolTargetsAdded.DeleteLabelValues(sp.config.JobName)
+		sp.metrics.targetScrapePoolSymbolTableItems.DeleteLabelValues(sp.config.JobName)
 		sp.metrics.targetSyncIntervalLength.DeleteLabelValues(sp.config.JobName)
 		sp.metrics.targetSyncFailed.DeleteLabelValues(sp.config.JobName)
 	}
@@ -273,6 +274,15 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) error {
 
 	sp.metrics.targetScrapePoolTargetLimit.WithLabelValues(sp.config.JobName).Set(float64(sp.config.TargetLimit))
 
+	sp.restartLoops(reuseCache)
+	oldClient.CloseIdleConnections()
+	sp.metrics.targetReloadIntervalLength.WithLabelValues(time.Duration(sp.config.ScrapeInterval).String()).Observe(
+		time.Since(start).Seconds(),
+	)
+	return nil
+}
+
+func (sp *scrapePool) restartLoops(reuseCache bool) {
 	var (
 		wg            sync.WaitGroup
 		interval      = time.Duration(sp.config.ScrapeInterval)
@@ -313,7 +323,7 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) error {
 				client:               sp.client,
 				timeout:              timeout,
 				bodySizeLimit:        bodySizeLimit,
-				acceptHeader:         acceptHeader(cfg.ScrapeProtocols),
+				acceptHeader:         acceptHeader(sp.config.ScrapeProtocols),
 				acceptEncodingHeader: acceptEncodingHeader(enableCompression),
 			}
 			newLoop = sp.newLoop(scrapeLoopOptions{
@@ -352,11 +362,10 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) error {
 	sp.targetMtx.Unlock()
 
 	wg.Wait()
-	oldClient.CloseIdleConnections()
-	sp.metrics.targetReloadIntervalLength.WithLabelValues(interval.String()).Observe(
-		time.Since(start).Seconds(),
-	)
+}
 
+// Must be called with sp.mtx held.
+func (sp *scrapePool) checkSymbolTable() {
 	// Here we take steps to clear out the symbol table if it has grown a lot.
 	// After waiting some time for things to settle, we take the size of the symbol-table.
 	// If, after some more time, the table has grown to twice that size, we start a new one.
@@ -367,11 +376,10 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) error {
 		} else if sp.symbolTable.Len() > 2*sp.initialSymbolTableLen {
 			sp.symbolTable = labels.NewSymbolTable()
 			sp.initialSymbolTableLen = 0
+			sp.restartLoops(false) // To drop all caches.
 		}
 		sp.lastSymbolTableCheck = time.Now()
 	}
-
-	return nil
 }
 
 // Sync converts target groups into actual scrape targets and synchronizes
@@ -408,8 +416,10 @@ func (sp *scrapePool) Sync(tgs []*targetgroup.Group) {
 			}
 		}
 	}
+	sp.metrics.targetScrapePoolSymbolTableItems.WithLabelValues(sp.config.JobName).Set(float64(sp.symbolTable.Len()))
 	sp.targetMtx.Unlock()
 	sp.sync(all)
+	sp.checkSymbolTable()
 
 	sp.metrics.targetSyncIntervalLength.WithLabelValues(sp.config.JobName).Observe(
 		time.Since(start).Seconds(),

tsdb/db.go

@@ -1407,6 +1407,9 @@ func (db *DB) compactHead(head *RangeHead) error {
 	if err = db.head.truncateMemory(head.BlockMaxTime()); err != nil {
 		return fmt.Errorf("head memory truncate: %w", err)
 	}
+
+	db.head.RebuildSymbolTable(db.logger)
+
 	return nil
 }
 

tsdb/head_dedupelabels.go

@@ -16,6 +16,9 @@
 package tsdb
 
 import (
+	"github.com/go-kit/log"
+	"github.com/go-kit/log/level"
+
 	"github.com/prometheus/prometheus/model/labels"
 )
 
@@ -25,3 +28,68 @@ func (s *memSeries) labels() labels.Labels {
 	defer s.Unlock()
 	return s.lset
 }
+
+// RebuildSymbolTable goes through all the series in h, build a SymbolTable with all names and values,
+// replace each series' Labels with one using that SymbolTable.
+func (h *Head) RebuildSymbolTable(logger log.Logger) *labels.SymbolTable {
+	level.Info(logger).Log("msg", "RebuildSymbolTable starting")
+	st := labels.NewSymbolTable()
+	builder := labels.NewScratchBuilderWithSymbolTable(st, 0)
+	rebuildLabels := func(lbls labels.Labels) labels.Labels {
+		builder.Reset()
+		lbls.Range(func(l labels.Label) {
+			builder.Add(l.Name, l.Value)
+		})
+		return builder.Labels()
+	}
+
+	for i := 0; i < h.series.size; i++ {
+		h.series.locks[i].Lock()
+
+		for _, s := range h.series.hashes[i].unique {
+			s.Lock()
+			s.lset = rebuildLabels(s.lset)
+			s.Unlock()
+		}
+
+		for _, all := range h.series.hashes[i].conflicts {
+			for _, s := range all {
+				s.Lock()
+				s.lset = rebuildLabels(s.lset)
+				s.Unlock()
+			}
+		}
+
+		h.series.locks[i].Unlock()
+	}
+	type withReset interface{ ResetSymbolTable(*labels.SymbolTable) }
+	if e, ok := h.exemplars.(withReset); ok {
+		e.ResetSymbolTable(st)
+	}
+	level.Info(logger).Log("msg", "RebuildSymbolTable finished", "size", st.Len())
+	return st
+}
+
+func (ce *CircularExemplarStorage) ResetSymbolTable(st *labels.SymbolTable) {
+	builder := labels.NewScratchBuilderWithSymbolTable(st, 0)
+	rebuildLabels := func(lbls labels.Labels) labels.Labels {
+		builder.Reset()
+		lbls.Range(func(l labels.Label) {
+			builder.Add(l.Name, l.Value)
+		})
+		return builder.Labels()
+	}
+
+	ce.lock.RLock()
+	defer ce.lock.RUnlock()
+
+	for _, v := range ce.index {
+		v.seriesLabels = rebuildLabels(v.seriesLabels)
+	}
+	for i := range ce.exemplars {
+		if ce.exemplars[i].ref == nil {
+			continue
+		}
+		ce.exemplars[i].exemplar.Labels = rebuildLabels(ce.exemplars[i].exemplar.Labels)
+	}
+}

tsdb/head_other.go

@@ -16,10 +16,17 @@
 package tsdb
 
 import (
+	"github.com/go-kit/log"
+
 	"github.com/prometheus/prometheus/model/labels"
 )
 
 // Helper method to access labels; trivial when not using dedupelabels.
 func (s *memSeries) labels() labels.Labels {
 	return s.lset
 }
+
+// No-op when not using dedupelabels.
+func (h *Head) RebuildSymbolTable(logger log.Logger) *labels.SymbolTable {
+	return nil
+}