Add a flag which allows the queriers to run completely standalone and…

… only query stored data. (grafana#3700)

docs/sources/configuration/_index.md

@@ -289,6 +289,11 @@ The `querier_config` block configures the Loki Querier.
 # CLI flag: -querier.query-ingesters-within
 [query_ingesters_within: <duration> | default = 0s]
 
+# Only query the store, do not attempt to query any ingesters,
+# useful for running a standalone querier pool opearting only against stored data.
+# CLI flag: -querier.query-store-only
+[query_store_only: <boolean> | default = false]
+
 # Configuration options for the LogQL engine.
 engine:
   # Timeout for query execution

pkg/loki/modules.go

@@ -326,6 +326,10 @@ func (t *Loki) initStore() (_ services.Service, err error) {
 		boltdbShipperMinIngesterQueryStoreDuration := boltdbShipperMinIngesterQueryStoreDuration(t.Cfg)
 		switch t.Cfg.Target {
 		case Querier, Ruler:
+			// Do not use the AsyncStore if the querier is configured with QueryStoreOnly set to true
+			if t.Cfg.Querier.QueryStoreOnly {
+				break
+			}
 			// Use AsyncStore to query both ingesters local store and chunk store for store queries.
 			// Only queriers should use the AsyncStore, it should never be used in ingesters.
 			chunkStore = loki_storage.NewAsyncStore(chunkStore, t.ingesterQuerier,

pkg/querier/querier.go

@@ -46,6 +46,7 @@ type Config struct {
 	IngesterQueryStoreMaxLookback time.Duration    `yaml:"-"`
 	Engine                        logql.EngineOpts `yaml:"engine,omitempty"`
 	MaxConcurrent                 int              `yaml:"max_concurrent"`
+	QueryStoreOnly                bool             `yaml:"query_store_only"`
 }
 
 // RegisterFlags register flags.
@@ -56,6 +57,7 @@ func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
 	f.DurationVar(&cfg.ExtraQueryDelay, "querier.extra-query-delay", 0, "Time to wait before sending more than the minimum successful query requests.")
 	f.DurationVar(&cfg.QueryIngestersWithin, "querier.query-ingesters-within", 0, "Maximum lookback beyond which queries are not sent to ingester. 0 means all queries are sent to ingester.")
 	f.IntVar(&cfg.MaxConcurrent, "querier.max-concurrent", 20, "The maximum number of concurrent queries.")
+	f.BoolVar(&cfg.QueryStoreOnly, "querier.query-store-only", false, "Queriers should only query the store and not try to query any ingesters")
 }
 
 // Querier handlers queries.
@@ -96,7 +98,7 @@ func (q *Querier) SelectLogs(ctx context.Context, params logql.SelectLogParams)
 	ingesterQueryInterval, storeQueryInterval := q.buildQueryIntervals(params.Start, params.End)
 
 	iters := []iter.EntryIterator{}
-	if ingesterQueryInterval != nil {
+	if !q.cfg.QueryStoreOnly && ingesterQueryInterval != nil {
 		// Make a copy of the request before modifying
 		// because the initial request is used below to query stores
 		queryRequestCopy := *params.QueryRequest
@@ -139,7 +141,7 @@ func (q *Querier) SelectSamples(ctx context.Context, params logql.SelectSamplePa
 	ingesterQueryInterval, storeQueryInterval := q.buildQueryIntervals(params.Start, params.End)
 
 	iters := []iter.SampleIterator{}
-	if ingesterQueryInterval != nil {
+	if !q.cfg.QueryStoreOnly && ingesterQueryInterval != nil {
 		// Make a copy of the request before modifying
 		// because the initial request is used below to query stores
 		queryRequestCopy := *params.SampleQueryRequest
@@ -261,9 +263,12 @@ func (q *Querier) Label(ctx context.Context, req *logproto.LabelRequest) (*logpr
 	ctx, cancel := context.WithDeadline(ctx, time.Now().Add(q.cfg.QueryTimeout))
 	defer cancel()
 
-	ingesterValues, err := q.ingesterQuerier.Label(ctx, req)
-	if err != nil {
-		return nil, err
+	var ingesterValues [][]string
+	if !q.cfg.QueryStoreOnly {
+		ingesterValues, err = q.ingesterQuerier.Label(ctx, req)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	from, through := model.TimeFromUnixNano(req.Start.UnixNano()), model.TimeFromUnixNano(req.End.UnixNano())
@@ -371,17 +376,20 @@ func (q *Querier) awaitSeries(ctx context.Context, req *logproto.SeriesRequest)
 	errs := make(chan error, 2)
 
 	// fetch series from ingesters and store concurrently
+	if q.cfg.QueryStoreOnly {
+		series <- [][]logproto.SeriesIdentifier{}
+	} else {
+		go func() {
+			// fetch series identifiers from ingesters
+			resps, err := q.ingesterQuerier.Series(ctx, req)
+			if err != nil {
+				errs <- err
+				return
+			}
 
-	go func() {
-		// fetch series identifiers from ingesters
-		resps, err := q.ingesterQuerier.Series(ctx, req)
-		if err != nil {
-			errs <- err
-			return
-		}
-
-		series <- resps
-	}()
+			series <- resps
+		}()
+	}
 
 	go func() {
 		storeValues, err := q.seriesForMatchers(ctx, req.Start, req.End, req.GetGroups())