Merge pull request #2079 from prometheus/fabxc-storage

storage: enhance Querier interface usage

promql/engine.go

@@ -218,20 +218,25 @@ func contextDone(ctx context.Context, env string) error {
 // Engine handles the lifetime of queries from beginning to end.
 // It is connected to a querier.
 type Engine struct {
-	// The querier on which the engine operates.
-	querier local.Querier
+	// A Querier constructor against an underlying storage.
+	queryable Queryable
 	// The gate limiting the maximum number of concurrent and waiting queries.
 	gate    *queryGate
 	options *EngineOptions
 }
 
+// Queryable allows opening a storage querier.
+type Queryable interface {
+	Querier() (local.Querier, error)
+}
+
 // NewEngine returns a new engine.
-func NewEngine(querier local.Querier, o *EngineOptions) *Engine {
+func NewEngine(queryable Queryable, o *EngineOptions) *Engine {
 	if o == nil {
 		o = DefaultEngineOptions
 	}
 	return &Engine{
-		querier: querier,
+		queryable: queryable,
 		gate:      newQueryGate(o.MaxConcurrentQueries),
 		options:   o,
 	}
@@ -351,13 +356,18 @@ func (ng *Engine) exec(ctx context.Context, q *query) (model.Value, error) {
 
 // execEvalStmt evaluates the expression of an evaluation statement for the given time range.
 func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (model.Value, error) {
+	querier, err := ng.queryable.Querier()
+	if err != nil {
+		return nil, err
+	}
+	defer querier.Close()
+
 	prepareTimer := query.stats.GetTimer(stats.QueryPreparationTime).Start()
-	err := ng.populateIterators(ctx, s)
+	err = ng.populateIterators(ctx, querier, s)
 	prepareTimer.Stop()
 	if err != nil {
 		return nil, err
 	}
-
 	defer ng.closeIterators(s)
 
 	evalTimer := query.stats.GetTimer(stats.InnerEvalTime).Start()
@@ -463,20 +473,20 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 	return resMatrix, nil
 }
 
-func (ng *Engine) populateIterators(ctx context.Context, s *EvalStmt) error {
+func (ng *Engine) populateIterators(ctx context.Context, querier local.Querier, s *EvalStmt) error {
 	var queryErr error
 	Inspect(s.Expr, func(node Node) bool {
 		switch n := node.(type) {
 		case *VectorSelector:
 			if s.Start.Equal(s.End) {
-				n.iterators, queryErr = ng.querier.QueryInstant(
+				n.iterators, queryErr = querier.QueryInstant(
 					ctx,
 					s.Start.Add(-n.Offset),
 					StalenessDelta,
 					n.LabelMatchers...,
 				)
 			} else {
-				n.iterators, queryErr = ng.querier.QueryRange(
+				n.iterators, queryErr = querier.QueryRange(
 					ctx,
 					s.Start.Add(-n.Offset-StalenessDelta),
 					s.End.Add(-n.Offset),
@@ -487,7 +497,7 @@ func (ng *Engine) populateIterators(ctx context.Context, s *EvalStmt) error {
 				return false
 			}
 		case *MatrixSelector:
-			n.iterators, queryErr = ng.querier.QueryRange(
+			n.iterators, queryErr = querier.QueryRange(
 				ctx,
 				s.Start.Add(-n.Offset-n.Range),
 				s.End.Add(-n.Offset),

storage/local/interface.go

@@ -26,7 +26,8 @@ import (
 // Storage ingests and manages samples, along with various indexes. All methods
 // are goroutine-safe. Storage implements storage.SampleAppender.
 type Storage interface {
-	Querier
+	// Querier returns a new Querier on the storage.
+	Querier() (Querier, error)
 
 	// This SampleAppender needs multiple samples for the same fingerprint to be
 	// submitted in chronological order, from oldest to newest. When Append has
@@ -57,6 +58,9 @@ type Storage interface {
 
 // Querier allows querying a time series storage.
 type Querier interface {
+	// Close closes the querier. Behavior for subsequent calls to Querier methods
+	// is undefined.
+	Close() error
 	// QueryRange returns a list of series iterators for the selected
 	// time range and label matchers. The iterators need to be closed
 	// after usage.

storage/local/noop_storage.go

@@ -40,23 +40,35 @@ func (s *NoopStorage) Stop() error {
 func (s *NoopStorage) WaitForIndexing() {
 }
 
-// LastSampleForLabelMatchers implements Storage.
-func (s *NoopStorage) LastSampleForLabelMatchers(ctx context.Context, cutoff model.Time, matcherSets ...metric.LabelMatchers) (model.Vector, error) {
+// Querier implements Storage.
+func (s *NoopStorage) Querier() (Querier, error) {
+	return &NoopQuerier{}, nil
+}
+
+type NoopQuerier struct{}
+
+// Close implements Querier.
+func (s *NoopQuerier) Close() error {
+	return nil
+}
+
+// LastSampleForLabelMatchers implements Querier.
+func (s *NoopQuerier) LastSampleForLabelMatchers(ctx context.Context, cutoff model.Time, matcherSets ...metric.LabelMatchers) (model.Vector, error) {
 	return nil, nil
 }
 
-// QueryRange implements Storage.
-func (s *NoopStorage) QueryRange(ctx context.Context, from, through model.Time, matchers ...*metric.LabelMatcher) ([]SeriesIterator, error) {
+// QueryRange implements Querier
+func (s *NoopQuerier) QueryRange(ctx context.Context, from, through model.Time, matchers ...*metric.LabelMatcher) ([]SeriesIterator, error) {
 	return nil, nil
 }
 
-// QueryInstant implements Storage.
-func (s *NoopStorage) QueryInstant(ctx context.Context, ts model.Time, stalenessDelta time.Duration, matchers ...*metric.LabelMatcher) ([]SeriesIterator, error) {
+// QueryInstant implements Querier.
+func (s *NoopQuerier) QueryInstant(ctx context.Context, ts model.Time, stalenessDelta time.Duration, matchers ...*metric.LabelMatcher) ([]SeriesIterator, error) {
 	return nil, nil
 }
 
-// MetricsForLabelMatchers implements Storage.
-func (s *NoopStorage) MetricsForLabelMatchers(
+// MetricsForLabelMatchers implements Querier.
+func (s *NoopQuerier) MetricsForLabelMatchers(
 	ctx context.Context,
 	from, through model.Time,
 	matcherSets ...metric.LabelMatchers,
@@ -64,8 +76,8 @@ func (s *NoopStorage) MetricsForLabelMatchers(
 	return nil, nil
 }
 
-// LabelValuesForLabelName implements Storage.
-func (s *NoopStorage) LabelValuesForLabelName(ctx context.Context, labelName model.LabelName) (model.LabelValues, error) {
+// LabelValuesForLabelName implements Querier.
+func (s *NoopQuerier) LabelValuesForLabelName(ctx context.Context, labelName model.LabelName) (model.LabelValues, error) {
 	return nil, nil
 }
 

storage/local/storage.go

@@ -403,6 +403,19 @@ func (s *MemorySeriesStorage) Stop() error {
 	return nil
 }
 
+type memorySeriesStorageQuerier struct {
+	*MemorySeriesStorage
+}
+
+func (memorySeriesStorageQuerier) Close() error {
+	return nil
+}
+
+// Querier implements the storage interface.
+func (s *MemorySeriesStorage) Querier() (Querier, error) {
+	return memorySeriesStorageQuerier{s}, nil
+}
+
 // WaitForIndexing implements Storage.
 func (s *MemorySeriesStorage) WaitForIndexing() {
 	s.persistence.waitForIndexing()

web/api/v1/api.go

@@ -226,7 +226,13 @@ func (api *API) labelValues(r *http.Request) (interface{}, *apiError) {
 	if !model.LabelNameRE.MatchString(name) {
 		return nil, &apiError{errorBadData, fmt.Errorf("invalid label name: %q", name)}
 	}
-	vals, err := api.Storage.LabelValuesForLabelName(api.context(r), model.LabelName(name))
+	q, err := api.Storage.Querier()
+	if err != nil {
+		return nil, &apiError{errorExec, err}
+	}
+	defer q.Close()
+
+	vals, err := q.LabelValuesForLabelName(api.context(r), model.LabelName(name))
 	if err != nil {
 		return nil, &apiError{errorExec, err}
 	}
@@ -272,7 +278,13 @@ func (api *API) series(r *http.Request) (interface{}, *apiError) {
 		matcherSets = append(matcherSets, matchers)
 	}
 
-	res, err := api.Storage.MetricsForLabelMatchers(api.context(r), start, end, matcherSets...)
+	q, err := api.Storage.Querier()
+	if err != nil {
+		return nil, &apiError{errorExec, err}
+	}
+	defer q.Close()
+
+	res, err := q.MetricsForLabelMatchers(api.context(r), start, end, matcherSets...)
 	if err != nil {
 		return nil, &apiError{errorExec, err}
 	}

web/federate.go

@@ -50,7 +50,14 @@ func (h *Handler) federation(w http.ResponseWriter, req *http.Request) {
 	)
 	w.Header().Set("Content-Type", string(format))
 
-	vector, err := h.storage.LastSampleForLabelMatchers(h.context, minTimestamp, matcherSets...)
+	q, err := h.storage.Querier()
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	defer q.Close()
+
+	vector, err := q.LastSampleForLabelMatchers(h.context, minTimestamp, matcherSets...)
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return