test(decom): cover keys below a key that the walk does not see

Signed-off-by: Denis Babchuk <babchukdenis@icloud.com>

cmd/erasure-server-pool-decom-keys-below_test.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2026 Denis Babchuk
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import "testing"
+
+// A key below another key ("k/b" under "k") is a directory inside the
+// directory of that key. The listing treats the directory of an object as a
+// leaf, so a decommission walk does not see "k/b" while "k" is still in the
+// pool. The walk has to be repeated once the keys above are gone, or the
+// check after the bucket finds them and the decommission fails.
+
+func keysBelowDecommission(t *testing.T, z *erasureServerPools) PoolDecommissionInfo {
+	t.Helper()
+	if err := z.StartDecommission(t.Context(), 0); err != nil {
+		t.Fatal(err)
+	}
+	z.doDecommissionInRoutine(t.Context(), 0)
+	z.poolMetaMutex.RLock()
+	defer z.poolMetaMutex.RUnlock()
+	return *z.poolMeta.Pools[0].Decommission
+}
+
+func keysBelowPools(t *testing.T) (*erasureServerPools, string, []string) {
+	t.Helper()
+	z, _ := migrationTestPools(t)
+	const bucket = "keys-below"
+	if err := z.MakeBucket(t.Context(), bucket, MakeBucketOptions{VersioningEnabled: true}); err != nil {
+		t.Fatal(err)
+	}
+	keys := []string{"k", "k/b", "k/b/c"}
+	for _, key := range keys {
+		putConsistencyObject(t, z, bucket, key, 0, key, ObjectOptions{Versioned: true})
+	}
+	return z, bucket, keys
+}
+
+func TestDecommissionMovesKeysBelowAKey(t *testing.T) {
+	z, bucket, keys := keysBelowPools(t)
+	if info := keysBelowDecommission(t, z); !info.Complete || info.Failed {
+		t.Errorf("decommission: complete %v, failed %v; want complete", info.Complete, info.Failed)
+	}
+	for _, key := range keys {
+		if _, err := z.serverPools[0].GetObjectInfo(t.Context(), bucket, key, ObjectOptions{}); !isErrObjectNotFound(err) {
+			t.Errorf("%s still in pool 0: %v", key, err)
+		}
+		if body := migrationTestBody(t, z.GetObjectNInfo, bucket, key, ""); body != key {
+			t.Errorf("%s reads %q", key, body)
+		}
+	}
+}