Stub a heap usage field on ClusterInfo

Author: ywangd

server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java

@@ -57,6 +57,13 @@ public class ClusterInfo implements ChunkedToXContent, Writeable {
     final Map<ShardId, Long> shardDataSetSizes;
     final Map<NodeAndShard, String> dataPath;
     final Map<NodeAndPath, ReservedSpace> reservedSpace;
+    private final Map<String, NodeHeapUsage> nodeHeapUsages = Map.of();
+
+    public record NodeHeapUsage(String nodeId, long usedInBytes, long totalInBytes) {
+        public double usedPercentage() {
+            return (usedInBytes * 100.0d) / totalInBytes;
+        }
+    }
 
     protected ClusterInfo() {
         this(Map.of(), Map.of(), Map.of(), Map.of(), Map.of(), Map.of());
@@ -211,6 +218,10 @@ public Map<String, DiskUsage> getNodeMostAvailableDiskUsages() {
         return this.mostAvailableSpaceUsage;
     }
 
+    public Map<String, NodeHeapUsage> getNodeHeapUsages() {
+        return nodeHeapUsages;
+    }
+
     /**
      * Returns the shard size for the given shardId or <code>null</code> if that metric is not available.
      */