scraping: re-use symbol table for scrape loops

One symbol table for all loops in the same scrape pool, i.e. from the
same job.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

scrape/scrape.go

@@ -163,6 +163,7 @@ func newScrapePool(cfg *config.ScrapeConfig, app storage.Appendable, offsetSeed
 			func(l labels.Labels) labels.Labels { return mutateReportSampleLabels(l, opts.target) },
 			func(ctx context.Context) storage.Appender { return app.Appender(ctx) },
 			cache,
+			sp.symbolTable,
 			offsetSeed,
 			opts.honorTimestamps,
 			opts.trackTimestampsStaleness,
@@ -809,6 +810,7 @@ type scrapeLoop struct {
 	enableCTZeroIngestion    bool
 
 	appender            func(ctx context.Context) storage.Appender
+	symbolTable         *labels.SymbolTable
 	sampleMutator       labelsMutator
 	reportSampleMutator labelsMutator
 
@@ -1088,6 +1090,7 @@ func newScrapeLoop(ctx context.Context,
 	reportSampleMutator labelsMutator,
 	appender func(ctx context.Context) storage.Appender,
 	cache *scrapeCache,
+	symbolTable *labels.SymbolTable,
 	offsetSeed uint64,
 	honorTimestamps bool,
 	trackTimestampsStaleness bool,
@@ -1133,6 +1136,7 @@ func newScrapeLoop(ctx context.Context,
 		buffers:                  buffers,
 		cache:                    cache,
 		appender:                 appender,
+		symbolTable:              symbolTable,
 		sampleMutator:            sampleMutator,
 		reportSampleMutator:      reportSampleMutator,
 		stopped:                  make(chan struct{}),
@@ -1431,7 +1435,7 @@ type appendErrors struct {
 }
 
 func (sl *scrapeLoop) append(app storage.Appender, b []byte, contentType string, ts time.Time) (total, added, seriesAdded int, err error) {
-	p, err := textparse.New(b, contentType, sl.scrapeClassicHistograms)
+	p, err := textparse.New(b, contentType, sl.scrapeClassicHistograms, sl.symbolTable)
 	if err != nil {
 		level.Debug(sl.l).Log(
 			"msg", "Invalid content type on scrape, using prometheus parser as fallback.",

scrape/scrape_test.go

@@ -660,6 +660,7 @@ func newBasicScrapeLoop(t testing.TB, ctx context.Context, scraper scraper, app
 		nopMutator,
 		app,
 		nil,
+		nil,
 		0,
 		true,
 		false,
@@ -800,6 +801,7 @@ func TestScrapeLoopRun(t *testing.T) {
 		nopMutator,
 		app,
 		nil,
+		nil,
 		0,
 		true,
 		false,
@@ -942,6 +944,7 @@ func TestScrapeLoopMetadata(t *testing.T) {
 		nopMutator,
 		func(ctx context.Context) storage.Appender { return nopAppender{} },
 		cache,
+		labels.NewSymbolTable(),
 		0,
 		true,
 		false,
@@ -1470,7 +1473,7 @@ func TestScrapeLoopAppendCacheEntryButErrNotFound(t *testing.T) {
 	fakeRef := storage.SeriesRef(1)
 	expValue := float64(1)
 	metric := []byte(`metric{n="1"} 1`)
-	p, warning := textparse.New(metric, "", false)
+	p, warning := textparse.New(metric, "", false, labels.NewSymbolTable())
 	require.NoError(t, warning)
 
 	var lset labels.Labels