Fix naming conventions and supplement UT

Author: lfxy

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java

@@ -217,6 +217,9 @@ private static INodeDirectory createRoot(FSNamesystem namesystem) {
   // authorizeWithContext() API or not.
   private boolean useAuthorizationWithContextAPI = false;
 
+  // We need a maximum maximum because by default, PB limits message sizes
+  // to 64MB. This means we can only store approximately 6.7 million entries
+  // per directory, but let's use 6.4 million for some safety.
   private static final int maxDirItemsLimit = 64 * 100 * 1000;
 
   public void setINodeAttributeProvider(
@@ -397,9 +400,6 @@ public enum DirOp {
     Preconditions.checkArgument(this.inodeXAttrsLimit >= 0,
         "Cannot set a negative limit on the number of xattrs per inode (%s).",
         DFSConfigKeys.DFS_NAMENODE_MAX_XATTRS_PER_INODE_KEY);
-    // We need a maximum maximum because by default, PB limits message sizes
-    // to 64MB. This means we can only store approximately 6.7 million entries
-    // per directory, but let's use 6.4 million for some safety.
     Preconditions.checkArgument(
         maxDirItems > 0 && maxDirItems <= maxDirItemsLimit, "Cannot set "
             + DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY
@@ -582,7 +582,7 @@ String setProtectedDirectories(String protectedDirsString) {
   }
 
   public void setMaxDirItems(int newVal) {
-    com.google.common.base.Preconditions.checkArgument(
+    Preconditions.checkArgument(
         newVal > 0 && newVal <= maxDirItemsLimit, "Cannot set "
             + DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY
             + " to a value less than 1 or greater than " + maxDirItemsLimit);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java

@@ -2391,7 +2391,7 @@ protected String reconfigurePropertyImpl(String property, String newVal)
         || property.equals(DFS_NAMENODE_WRITE_LOCK_REPORTING_THRESHOLD_MS_KEY)) {
       return reconfigureFSNamesystemLockMetricsParameters(property, newVal);
     } else if (property.equals(DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY)) {
-      return reconfMaxDirItems(newVal);
+      return reconfigureMaxDirItems(newVal);
     } else {
       throw new ReconfigurationException(property, newVal, getConf().get(
           property));
@@ -2810,7 +2810,7 @@ private String reconfigureFSNamesystemLockMetricsParameters(final String propert
     }
   }
 
-  private String reconfMaxDirItems(String newVal) throws ReconfigurationException {
+  private String reconfigureMaxDirItems(String newVal) throws ReconfigurationException {
     int newSetting;
     namesystem.writeLock(RwLockMode.BM);
     try {
@@ -2823,7 +2823,7 @@ private String reconfMaxDirItems(String newVal) throws ReconfigurationException
       throw new ReconfigurationException(DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY, newVal,
           getConf().get(DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY), e);
     } finally {
-      namesystem.writeUnlock(RwLockMode.BM, "reconfMaxDirItems");
+      namesystem.writeUnlock(RwLockMode.BM, "reconfigureMaxDirItems");
     }
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeReconfigure.java

@@ -867,20 +867,32 @@ public void testReconfigureSlowPeerCollectInterval() throws Exception {
   }
 
   @Test
-  public void testReconfigureMaxDirItems()
-      throws ReconfigurationException {
+  public void testReconfigureMaxDirItems() throws ReconfigurationException {
     final NameNode nameNode = cluster.getNameNode();
     final FSDirectory fsd = nameNode.namesystem.getFSDirectory();
 
-    // By default, DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY is 1024*1024.
-    assertEquals(1024*1024, fsd.getMaxDirItems());
+    // By default, DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY is 1024 * 1024.
+    assertEquals(1024 * 1024, fsd.getMaxDirItems());
 
     // Reconfigure.
-    nameNode.reconfigureProperty(
-        DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY, Integer.toString(1024*1024*2));
+    nameNode.reconfigureProperty(DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY,
+        Integer.toString(1024 * 1024 * 2));
 
-    // Assert DFS_NAMENODE_MAX_SLOWPEER_COLLECT_NODES_KEY is 10.
-    assertEquals(1024*1024*2, fsd.getMaxDirItems());
+    // Assert DFS_NAMENODE_MAX_SLOWPEER_COLLECT_NODES_KEY is 1024 * 1024 * 2.
+    assertEquals(1024 * 1024 * 2, fsd.getMaxDirItems());
+
+    try {
+      // Reconfigure to negative, and expect failed.
+      nameNode.reconfigureProperty(DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY,
+          Integer.toString(1024 * 1024 * -1));
+    } catch (ReconfigurationException e) {
+      assertEquals("Could not change property " +
+          "dfs.namenode.fs-limits.max-directory-items from '" + 1024 * 1024 * 2
+          + "' to '" + 1024 * 1024 * -1 + "'", e.getMessage());
+    }
+
+    // Assert DFS_NAMENODE_MAX_SLOWPEER_COLLECT_NODES_KEY is also 1024 * 1024 * 2.
+    assertEquals(1024 * 1024 * 2, fsd.getMaxDirItems());
   }
 
   @AfterEach