Deterministic response order of _security/stats/

Author: szybia

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authz/store/CompositeRolesStore.java

@@ -65,6 +65,7 @@
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -670,7 +671,9 @@ Iterable<ProjectScoped<RoleKey>> cachedRoles() {
     }
 
     public Map<String, Object> usageStatsWithJustDls() {
-        return Map.of("dls", Map.of("bit_set_cache", dlsBitsetCache.usageStats()));
+        // LinkedHashMap for ordering in transport.
+        // if adding properties consider consistent ordering for human-readability of JSON.
+        return Map.of("dls", Map.of("bit_set_cache", new LinkedHashMap<>(dlsBitsetCache.usageStats())));
     }
 
     public void usageStats(ActionListener<Map<String, Object>> listener) {