release-25.2: roachtest/clusterstats: ignore PromQL info-level annotations

pkg/cmd/roachtest/clusterstats/BUILD.bazel

@@ -41,6 +41,7 @@ go_library(
 go_test(
     name = "clusterstats_test",
     srcs = [
+        "collector_test.go",
         "exporter_test.go",
         "streamer_test.go",
         ":mock_client",  # keep

pkg/cmd/roachtest/clusterstats/collector.go

@@ -7,6 +7,7 @@ package clusterstats
 
 import (
 	"context"
+	"strings"
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/roachprod/logger"
@@ -95,8 +96,8 @@ func (cs *clusterStatCollector) CollectPoint(
 	if err != nil {
 		return nil, err
 	}
-	if len(warnings) > 0 {
-		return nil, errors.Newf("found warnings querying prometheus: %s", warnings)
+	if err := handlePromWarnings(ctx, l, q, warnings); err != nil {
+		return nil, err
 	}
 
 	fromVec := fromVal.(model.Vector)
@@ -169,8 +170,8 @@ func (cs *clusterStatCollector) CollectInterval(
 	if err != nil {
 		return nil, err
 	}
-	if len(warnings) > 0 {
-		return nil, errors.Newf("found warnings querying prometheus: %s", warnings)
+	if err := handlePromWarnings(ctx, l, q, warnings); err != nil {
+		return nil, err
 	}
 
 	fromMatrixTagged := fromVal.(model.Matrix)
@@ -210,3 +211,38 @@ func (cs *clusterStatCollector) CollectInterval(
 
 	return result, nil
 }
+
+// handlePromWarnings classifies the annotations returned alongside a Prometheus
+// query result. Prometheus annotations come in two flavors, identified by the
+// prefix on the wire:
+//
+//   - "PromQL info: ..." annotations are informational (e.g. a counter-named
+//     metric lint emitted since Prometheus 2.53). The query result is still
+//     valid; we log these and continue.
+//   - "PromQL warning: ..." annotations indicate a likely problem with the
+//     query (e.g. mismatched histogram operations) where Prometheus may have
+//     dropped result elements. Any other unrecognized annotation (e.g. legacy
+//     remote-read warnings, which predate the PromQL annotation system) is
+//     treated the same way to preserve the prior fail-loud behavior.
+//
+// The returned error, if any, matches the format used historically so existing
+// callers and log scrapers see the same string.
+func handlePromWarnings(
+	ctx context.Context, l *logger.Logger, q string, warnings promv1.Warnings,
+) error {
+	if len(warnings) == 0 {
+		return nil
+	}
+	var serious promv1.Warnings
+	for _, w := range warnings {
+		if strings.HasPrefix(w, "PromQL info:") {
+			l.PrintfCtx(ctx, "prometheus info querying %q: %s", q, w)
+			continue
+		}
+		serious = append(serious, w)
+	}
+	if len(serious) == 0 {
+		return nil
+	}
+	return errors.Newf("found warnings querying prometheus: %s", serious)
+}

pkg/cmd/roachtest/clusterstats/collector_test.go

@@ -0,0 +1,68 @@
+// Copyright 2026 The Cockroach Authors.
+//
+// Use of this software is governed by the CockroachDB Software License
+// included in the /LICENSE file.
+
+package clusterstats
+
+import (
+	"context"
+	"testing"
+
+	"github.com/cockroachdb/cockroach/pkg/roachprod/logger"
+	promv1 "github.com/prometheus/client_golang/api/prometheus/v1"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHandlePromWarnings(t *testing.T) {
+	const (
+		// Sample annotations as emitted by Prometheus 2.53+.
+		infoNotCounter   = `PromQL info: metric might not be a counter, name does not end in _total/_sum/_count/_bucket: "sys_host_disk_write_bytes" (1:6)`
+		warnGaugeHist    = `PromQL warning: rate() applied to gauge histogram has undefined semantics`
+		legacyRemoteRead = `remote read failed: partial response`
+	)
+
+	tests := []struct {
+		name        string
+		warnings    promv1.Warnings
+		expectedErr string
+	}{
+		{
+			name:     "no warnings",
+			warnings: nil,
+		},
+		{
+			name:     "only info is silenced",
+			warnings: promv1.Warnings{infoNotCounter},
+		},
+		{
+			name:        "warning is still fatal",
+			warnings:    promv1.Warnings{warnGaugeHist},
+			expectedErr: "found warnings querying prometheus: [" + warnGaugeHist + "]",
+		},
+		{
+			name:        "unprefixed annotation is treated as warning",
+			warnings:    promv1.Warnings{legacyRemoteRead},
+			expectedErr: "found warnings querying prometheus: [" + legacyRemoteRead + "]",
+		},
+		{
+			name:        "info filtered out, warning preserved",
+			warnings:    promv1.Warnings{infoNotCounter, warnGaugeHist},
+			expectedErr: "found warnings querying prometheus: [" + warnGaugeHist + "]",
+		},
+	}
+
+	l, err := (&logger.Config{}).NewLogger("")
+	require.NoError(t, err)
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			err := handlePromWarnings(context.Background(), l, "q", tc.warnings)
+			if tc.expectedErr == "" {
+				require.NoError(t, err)
+			} else {
+				require.EqualError(t, err, tc.expectedErr)
+			}
+		})
+	}
+}