chore: shard limited queries with a fixed sharding factor (grafana#13576

)

Signed-off-by: Edward Welch <[email protected]>

pkg/querier/queryrange/roundtrip.go

@@ -206,7 +206,7 @@ func NewMiddleware(
 		return nil, nil, err
 	}
 
-	limitedTripperware, err := NewLimitedTripperware(cfg, log, limits, schema, metrics, codec, iqo, metricsNamespace)
+	limitedTripperware, err := NewLimitedTripperware(cfg, engineOpts, log, limits, schema, metrics, codec, iqo, indexStatsTripperware, metricsNamespace)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -615,14 +615,35 @@ func NewLogFilterTripperware(cfg Config, engineOpts logql.EngineOpts, log log.Lo
 }
 
 // NewLimitedTripperware creates a new frontend tripperware responsible for handling log requests which are label matcher only, no filter expression.
-func NewLimitedTripperware(cfg Config, log log.Logger, limits Limits, schema config.SchemaConfig, metrics *Metrics, merger base.Merger, iqo util.IngesterQueryOptions, metricsNamespace string) (base.Middleware, error) {
+func NewLimitedTripperware(cfg Config, engineOpts logql.EngineOpts, log log.Logger, limits Limits, schema config.SchemaConfig, metrics *Metrics, merger base.Merger, iqo util.IngesterQueryOptions, indexStatsTripperware base.Middleware, metricsNamespace string) (base.Middleware, error) {
 	return base.MiddlewareFunc(func(next base.Handler) base.Handler {
+		statsHandler := indexStatsTripperware.Wrap(next)
+
 		queryRangeMiddleware := []base.Middleware{
 			StatsCollectorMiddleware(),
 			NewLimitsMiddleware(limits),
 			base.InstrumentMiddleware("split_by_interval", metrics.InstrumentMiddlewareMetrics),
 			SplitByIntervalMiddleware(schema.Configs, WithMaxParallelism(limits, limitedQuerySplits), merger, newDefaultSplitter(limits, iqo), metrics.SplitByMetrics),
 		}
+
+		if cfg.ShardedQueries {
+			queryRangeMiddleware = append(queryRangeMiddleware,
+				NewQueryShardMiddleware(
+					log,
+					schema.Configs,
+					engineOpts,
+					metrics.InstrumentMiddlewareMetrics, // instrumentation is included in the sharding middleware
+					metrics.MiddlewareMapperMetrics.shardMapper,
+					limits,
+					// Too many shards on limited queries results in slowing down this type of query
+					// and overwhelming the frontend, therefore we fix the number of shards to prevent this.
+					32, // 0 is unlimited shards
+					statsHandler,
+					cfg.ShardAggregations,
+				),
+			)
+		}
+
 		if cfg.MaxRetries > 0 {
 			queryRangeMiddleware = append(
 				queryRangeMiddleware, base.InstrumentMiddleware("retry", metrics.InstrumentMiddlewareMetrics),