HDFS-13167. DatanodeAdminManager Improvements. Contributed by BELUGA BEHR.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeAdminManager.java

@@ -21,8 +21,9 @@ import static com.google.common.base.Preconditions.checkArgument;
 import static org.apache.hadoop.util.Time.monotonicNow;
 
 import java.util.AbstractList;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
 import java.util.Iterator;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Queue;
@@ -139,7 +140,7 @@ public class DatanodeAdminManager {
         new ThreadFactoryBuilder().setNameFormat("DatanodeAdminMonitor-%d")
             .setDaemon(true).build());
     outOfServiceNodeBlocks = new TreeMap<>();
-    pendingNodes = new LinkedList<>();
+    pendingNodes = new ArrayDeque<>();
   }
 
   /**
@@ -219,7 +220,7 @@ public class DatanodeAdminManager {
         pendingNodes.add(node);
       }
     } else {
-      LOG.trace("startDecommission: Node {} in {}, nothing to do." +
+      LOG.trace("startDecommission: Node {} in {}, nothing to do.",
           node, node.getAdminState());
     }
   }
@@ -242,7 +243,7 @@ public class DatanodeAdminManager {
       pendingNodes.remove(node);
       outOfServiceNodeBlocks.remove(node);
     } else {
-      LOG.trace("stopDecommission: Node {} in {}, nothing to do." +
+      LOG.trace("stopDecommission: Node {} in {}, nothing to do.",
           node, node.getAdminState());
     }
   }
@@ -272,7 +273,7 @@ public class DatanodeAdminManager {
       // IN_MAINTENANCE to support maintenance expiration.
       pendingNodes.add(node);
     } else {
-      LOG.trace("startMaintenance: Node {} in {}, nothing to do." +
+      LOG.trace("startMaintenance: Node {} in {}, nothing to do.",
           node, node.getAdminState());
     }
   }
@@ -321,7 +322,7 @@ public class DatanodeAdminManager {
       pendingNodes.remove(node);
       outOfServiceNodeBlocks.remove(node);
     } else {
-      LOG.trace("stopMaintenance: Node {} in {}, nothing to do." +
+      LOG.trace("stopMaintenance: Node {} in {}, nothing to do.",
           node, node.getAdminState());
     }
   }
@@ -395,7 +396,7 @@ public class DatanodeAdminManager {
     for (DatanodeStorageInfo storage : storages) {
       final DatanodeDescriptor node = storage.getDatanodeDescriptor();
       nodeList.append(node);
-      nodeList.append(" ");
+      nodeList.append(' ');
     }
     NameNode.blockStateChangeLog.info(
         "Block: " + block + ", Expected Replicas: "
@@ -517,7 +518,7 @@ public class DatanodeAdminManager {
       final Iterator<Map.Entry<DatanodeDescriptor, AbstractList<BlockInfo>>>
           it = new CyclicIteration<>(outOfServiceNodeBlocks,
               iterkey).iterator();
-      final LinkedList<DatanodeDescriptor> toRemove = new LinkedList<>();
+      final List<DatanodeDescriptor> toRemove = new ArrayList<>();
 
       while (it.hasNext() && !exceededNumBlocksPerCheck() && namesystem
           .isRunning()) {
@@ -583,12 +584,12 @@ public class DatanodeAdminManager {
                   "A node is in an invalid state!");
             }
             LOG.debug("Node {} is sufficiently replicated and healthy, "
-                + "marked as {}.", dn.getAdminState());
+                + "marked as {}.", dn, dn.getAdminState());
           } else {
             LOG.debug("Node {} {} healthy."
                 + " It needs to replicate {} more blocks."
                 + " {} is still in progress.", dn,
-                isHealthy? "is": "isn't", blocks.size(), dn.getAdminState());
+                isHealthy ? "is": "isn't", blocks.size(), dn.getAdminState());
           }
         } else {
           LOG.debug("Node {} still has {} blocks to replicate "
@@ -744,10 +745,10 @@ public class DatanodeAdminManager {
         lowRedundancyBlocks++;
         if (bc.isUnderConstruction()) {
           INode ucFile = namesystem.getFSDirectory().getInode(bc.getId());
-          if(!(ucFile instanceof  INodeFile) ||
+          if (!(ucFile instanceof  INodeFile) ||
               !ucFile.asFile().isUnderConstruction()) {
-            LOG.warn("File " + ucFile.getLocalName() + " is not under " +
-                "construction. Skipping add to low redundancy open files!");
+            LOG.warn("File {} is not under construction. Skipping add to " +
+                "low redundancy open files!", ucFile.getLocalName());
           } else {
             lowRedundancyBlocksInOpenFiles++;
             lowRedundancyOpenFiles.add(ucFile.getId());