HDDS-10869. SCMNodeManager#getUsageInfo memory occupancy optimization

hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/node/NodeStateManager.java

@@ -682,6 +682,11 @@ public Set<ContainerID> getContainers(UUID uuid)
     return nodeStateMap.getContainers(uuid);
   }
 
+  public int getContainerCount(UUID uuid)
+      throws NodeNotFoundException {
+    return nodeStateMap.getContainerCount(uuid);
+  }
+
   /**
    * Move Stale or Dead node to healthy if we got a heartbeat from them.
    * Move healthy nodes to stale nodes if it is needed.

hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/node/SCMNodeManager.java

@@ -980,8 +980,7 @@ public DatanodeUsageInfo getUsageInfo(DatanodeDetails dn) {
     SCMNodeStat stat = getNodeStatInternal(dn);
     DatanodeUsageInfo usageInfo = new DatanodeUsageInfo(dn, stat);
     try {
-      int containerCount = getContainers(dn).size();
-      usageInfo.setContainerCount(containerCount);
+      usageInfo.setContainerCount(getContainerCount(dn));
     } catch (NodeNotFoundException ex) {
       LOG.error("Unknown datanode {}.", dn, ex);
     }
@@ -1458,6 +1457,11 @@ public Set<ContainerID> getContainers(DatanodeDetails datanodeDetails)
     return nodeStateManager.getContainers(datanodeDetails.getUuid());
   }
 
+  public int getContainerCount(DatanodeDetails datanodeDetails)
+      throws NodeNotFoundException {
+    return nodeStateManager.getContainerCount(datanodeDetails.getUuid());
+  }
+
   @Override
   public void addDatanodeCommand(UUID dnId, SCMCommand command) {
     writeLock().lock();

hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/node/states/NodeStateMap.java

@@ -378,6 +378,16 @@ public Set<ContainerID> getContainers(UUID uuid)
     }
   }
 
+  public int getContainerCount(UUID uuid) throws NodeNotFoundException {
+    lock.readLock().lock();
+    try {
+      checkIfNodeExist(uuid);
+      return nodeToContainer.get(uuid).size();
+    } finally {
+      lock.readLock().unlock();
+    }
+  }
+
   public void removeContainer(UUID uuid, ContainerID containerID) throws
       NodeNotFoundException {
     lock.writeLock().lock();

hadoop-ozone/recon/src/main/java/org/apache/hadoop/ozone/recon/api/NodeEndpoint.java

@@ -152,9 +152,7 @@ public Response getDatanodes() {
         }
       });
       try {
-        Set<ContainerID> allContainers = nodeManager.getContainers(datanode);
-
-        builder.withContainers(allContainers.size());
+        builder.withContainers(nodeManager.getContainerCount(datanode));
         builder.withOpenContainers(openContainers.get());
       } catch (NodeNotFoundException ex) {
         LOG.warn("Cannot get containers, datanode {} not found.",