Merge #135122

135122: storage: don't cache benchmark fixtures in metamorphic builds r=RaduBerinde a=jbowens

In CI, we sometimes run benchmarks in metamorphic builds to ensure the benchmarks pass. We don't want to cache the fixtures generated by these runs, because we may end up caching fixtures that reflect metamorphic values. This can lead to very non-deterministic behavior in the benchmarks depending on what metamorphic settings were active when the fixture was generated.

Epic: none
Release note: none
Informs #135114.

Co-authored-by: Jackson Owens <[email protected]>

pkg/storage/bench_data_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/encoding"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
+	"github.com/cockroachdb/cockroach/pkg/util/metamorphic"
 	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 	"github.com/cockroachdb/pebble/vfs"
 	"github.com/stretchr/testify/require"
@@ -69,9 +70,23 @@ func getInitialStateEngine(
 	ctx context.Context, b *testing.B, initial initialState, inMemory bool,
 ) Engine {
 	name := strings.Join(initial.Key(), "-")
-	dir := testfixtures.ReuseOrGenerate(b, name, func(dir string) {
+
+	// In CI, we sometimes run benchmarks in metamorphic builds to ensure the
+	// benchmarks pass. We don't want to cache the fixtures generated by these
+	// runs, because we may end up caching fixtures that reflect metamorphic
+	// values. This can lead to very non-deterministic behavior in the
+	// benchmarks depending on what metamorphic settings were active when the
+	// fixture was generated.
+	var dir string
+	if metamorphic.IsMetamorphicBuild() {
+		b.Log("running in metamorphic build; ignoring existing fixtures and not caching new ones")
+		dir = b.TempDir()
 		buildInitialState(ctx, b, initial, dir)
-	})
+	} else {
+		dir = testfixtures.ReuseOrGenerate(b, name, func(dir string) {
+			buildInitialState(ctx, b, initial, dir)
+		})
+	}
 	dataDir := filepath.Join(dir, "data")
 
 	opts := append([]ConfigOption{