Early Request Validation in Query Frontend (#10093)

* WIP sketch out validation roundtripper with existing metrics and labels query codecs

* lint: license header

* separate series request roundtrippers

* introduce request validation roundtripper tests

* lint import order

* introduce & test cardinality query validation in frontend roundtripper; expand metrics query tests to cover instant queries

* CHANGELOG

Author: francoposa

CHANGELOG.md

@@ -78,6 +78,7 @@
 * [ENHANCEMENT] Distributor: allow a different limit for info series (series ending in `_info`) label count, via `-validation.max-label-names-per-info-series`. #10028
 * [ENHANCEMENT] Ingester: do not reuse labels, samples and histograms slices in the write request if there are more entries than 10x the pre-allocated size. This should help to reduce the in-use memory in case of few requests with a very large number of labels, samples or histograms. #10040
 * [ENHANCEMENT] Query-Frontend: prune `<subquery> and on() (vector(x)==y)` style queries and stop pruning `<subquery> < -Inf`. Triggered by https://github.com/prometheus/prometheus/pull/15245. #10026
+* [ENHANCEMENT] Query-Frontend: perform request format validation before processing the request. #10093
 * [BUGFIX] Fix issue where functions such as `rate()` over native histograms could return incorrect values if a float stale marker was present in the selected range. #9508
 * [BUGFIX] Fix issue where negation of native histograms (eg. `-some_native_histogram_series`) did nothing. #9508
 * [BUGFIX] Fix issue where `metric might not be a counter, name does not end in _total/_sum/_count/_bucket` annotation would be emitted even if `rate` or `increase` did not have enough samples to compute a result. #9508

pkg/frontend/querymiddleware/codec.go

@@ -8,6 +8,7 @@ package querymiddleware
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -32,6 +33,7 @@ import (
 	"golang.org/x/exp/slices"
 
 	apierror "github.com/grafana/mimir/pkg/api/error"
+	"github.com/grafana/mimir/pkg/cardinality"
 	"github.com/grafana/mimir/pkg/mimirpb"
 	"github.com/grafana/mimir/pkg/querier/api"
 	"github.com/grafana/mimir/pkg/querier/stats"
@@ -582,6 +584,39 @@ func DecodeLabelsSeriesQueryTimeParams(reqValues *url.Values) (start, end int64,
 	return start, end, err
 }
 
+// DecodeCardinalityQueryParams strictly handles validation for cardinality API endpoint parameters.
+// The current decoding of the cardinality requests is handled in the cardinality package
+// which is not yet compatible with the codec's approach of using interfaces
+// and multiple concrete proto implementations to represent different query types.
+func DecodeCardinalityQueryParams(r *http.Request) (any, error) {
+	var err error
+
+	reqValues, err := util.ParseRequestFormWithoutConsumingBody(r)
+	if err != nil {
+		return nil, apierror.New(apierror.TypeBadData, err.Error())
+	}
+
+	var parsedReq any
+	switch {
+	case strings.HasSuffix(r.URL.Path, cardinalityLabelNamesPathSuffix):
+		parsedReq, err = cardinality.DecodeLabelNamesRequestFromValues(reqValues)
+
+	case strings.HasSuffix(r.URL.Path, cardinalityLabelValuesPathSuffix):
+		parsedReq, err = cardinality.DecodeLabelValuesRequestFromValues(reqValues)
+
+	case strings.HasSuffix(r.URL.Path, cardinalityActiveSeriesPathSuffix):
+		parsedReq, err = cardinality.DecodeActiveSeriesRequestFromValues(reqValues)
+
+	default:
+		return nil, errors.New("unknown cardinality API endpoint")
+	}
+
+	if err != nil {
+		return nil, apierror.New(apierror.TypeBadData, err.Error())
+	}
+	return parsedReq, nil
+}
+
 func decodeQueryMinMaxTime(queryExpr parser.Expr, start, end, step int64, lookbackDelta time.Duration) (minTime, maxTime int64) {
 	evalStmt := &parser.EvalStmt{
 		Expr:          queryExpr,

pkg/frontend/querymiddleware/request_validation.go

@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package querymiddleware
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/grafana/dskit/cancellation"
+)
+
+const requestValidationFailedFmt = "request validation failed for "
+
+var errMetricsQueryRequestValidationFailed = cancellation.NewErrorf(
+	requestValidationFailedFmt + "metrics query",
+)
+var errLabelsQueryRequestValidationFailed = cancellation.NewErrorf(
+	requestValidationFailedFmt + "labels query",
+)
+var errCardinalityQueryRequestValidationFailed = cancellation.NewErrorf(
+	requestValidationFailedFmt + "cardinality query",
+)
+
+type MetricsQueryRequestValidationRoundTripper struct {
+	codec Codec
+	next  http.RoundTripper
+}
+
+func NewMetricsQueryRequestValidationRoundTripper(codec Codec, next http.RoundTripper) http.RoundTripper {
+	return MetricsQueryRequestValidationRoundTripper{
+		codec: codec,
+		next:  next,
+	}
+}
+
+func (rt MetricsQueryRequestValidationRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	ctx, cancel := context.WithCancelCause(r.Context())
+	defer cancel(errMetricsQueryRequestValidationFailed)
+	r = r.WithContext(ctx)
+
+	_, err := rt.codec.DecodeMetricsQueryRequest(ctx, r)
+	if err != nil {
+		return nil, err
+	}
+	return rt.next.RoundTrip(r)
+}
+
+type LabelsQueryRequestValidationRoundTripper struct {
+	codec Codec
+	next  http.RoundTripper
+}
+
+func NewLabelsQueryRequestValidationRoundTripper(codec Codec, next http.RoundTripper) http.RoundTripper {
+	return LabelsQueryRequestValidationRoundTripper{
+		codec: codec,
+		next:  next,
+	}
+}
+
+func (rt LabelsQueryRequestValidationRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	ctx, cancel := context.WithCancelCause(r.Context())
+	defer cancel(errLabelsQueryRequestValidationFailed)
+	r = r.WithContext(ctx)
+
+	_, err := rt.codec.DecodeLabelsQueryRequest(ctx, r)
+	if err != nil {
+		return nil, err
+	}
+	return rt.next.RoundTrip(r)
+}
+
+type CardinalityQueryRequestValidationRoundTripper struct {
+	next http.RoundTripper
+}
+
+func NewCardinalityQueryRequestValidationRoundTripper(next http.RoundTripper) http.RoundTripper {
+	return CardinalityQueryRequestValidationRoundTripper{
+		next: next,
+	}
+}
+
+func (rt CardinalityQueryRequestValidationRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	ctx, cancel := context.WithCancelCause(r.Context())
+	defer cancel(errCardinalityQueryRequestValidationFailed)
+	r = r.WithContext(ctx)
+
+	_, err := DecodeCardinalityQueryParams(r)
+	if err != nil {
+		return nil, err
+	}
+	return rt.next.RoundTrip(r)
+}