HDFS-6102. Lower the default maximum items per directory to fix PB fsimage loading. Contributed by Andrew Wang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1577429 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -376,6 +376,9 @@ Release 2.4.0 - UNRELEASED
     HDFS-6097. zero-copy reads are incorrectly disabled on file offsets above
     2GB (cmccabe)
 
+    HDFS-6102. Lower the default maximum items per directory to fix PB fsimage
+    loading. (wang)
+
   BREAKDOWN OF HDFS-5698 SUBTASKS AND RELATED JIRAS
 
     HDFS-5717. Save FSImage header in protobuf. (Haohui Mai via jing9)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -283,9 +283,9 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
 
   //Filesystem limit keys
   public static final String  DFS_NAMENODE_MAX_COMPONENT_LENGTH_KEY = "dfs.namenode.fs-limits.max-component-length";
-  public static final int     DFS_NAMENODE_MAX_COMPONENT_LENGTH_DEFAULT = 0; // no limit
+  public static final int     DFS_NAMENODE_MAX_COMPONENT_LENGTH_DEFAULT = 255;
   public static final String  DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY = "dfs.namenode.fs-limits.max-directory-items";
-  public static final int     DFS_NAMENODE_MAX_DIRECTORY_ITEMS_DEFAULT = 0; // no limit
+  public static final int     DFS_NAMENODE_MAX_DIRECTORY_ITEMS_DEFAULT = 1024*1024;
   public static final String  DFS_NAMENODE_MIN_BLOCK_SIZE_KEY = "dfs.namenode.fs-limits.min-block-size";
   public static final long    DFS_NAMENODE_MIN_BLOCK_SIZE_DEFAULT = 1024*1024;
   public static final String  DFS_NAMENODE_MAX_BLOCKS_PER_FILE_KEY = "dfs.namenode.fs-limits.max-blocks-per-file";

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

@@ -188,6 +188,14 @@ public class FSDirectory implements Closeable {
     this.maxDirItems = conf.getInt(
         DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY,
         DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_DEFAULT);
+    // 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.
+    final int MAX_DIR_ITEMS = 64 * 100 * 1000;
+    Preconditions.checkArgument(
+        maxDirItems > 0 && maxDirItems <= MAX_DIR_ITEMS, "Cannot set "
+            + DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY
+            + " to a value less than 0 or greater than " + MAX_DIR_ITEMS);
 
     int threshold = conf.getInt(
         DFSConfigKeys.DFS_NAMENODE_NAME_CACHE_THRESHOLD_KEY,
@@ -2180,9 +2188,6 @@ public class FSDirectory implements Closeable {
    */
   void verifyMaxDirItems(INode[] pathComponents, int pos)
       throws MaxDirectoryItemsExceededException {
-    if (maxDirItems == 0) {
-      return;
-    }
 
     final INodeDirectory parent = pathComponents[pos-1].asDirectory();
     final int count = parent.getChildrenList(Snapshot.CURRENT_STATE_ID).size();

hadoop-hdfs-project/hadoop-hdfs/src/main/proto/fsimage.proto

@@ -173,6 +173,10 @@ message FilesUnderConstructionSection {
  * NAME: INODE_DIR
  */
 message INodeDirectorySection {
+  /**
+   * A single DirEntry needs to fit in the default PB max message size of
+   * 64MB. Please be careful when adding more fields to a DirEntry!
+   */
   message DirEntry {
     optional uint64 parent = 1;
     // children that are not reference nodes

hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto

@@ -352,6 +352,12 @@ message CheckpointCommandProto {
 
 /**
  * Block information
+ *
+ * Please be wary of adding additional fields here, since INodeFiles
+ * need to fit in PB's default max message size of 64MB.
+ * We restrict the max # of blocks per file
+ * (dfs.namenode.fs-limits.max-blocks-per-file), but it's better
+ * to avoid changing this.
  */
 message BlockProto {
   required uint64 blockId = 1;

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -288,7 +288,7 @@
 
 <property>
   <name>dfs.namenode.fs-limits.max-directory-items</name>
-  <value>0</value>
+  <value>1048576</value>
   <description>Defines the maximum number of items that a directory may
       contain.  A value of 0 will disable the check.</description>
 </property>

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

@@ -37,6 +37,7 @@ import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.protocol.FSLimitException.MaxDirectoryItemsExceededException;
 import org.apache.hadoop.hdfs.protocol.FSLimitException.PathComponentTooLongException;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
+import org.apache.hadoop.test.GenericTestUtils;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -82,22 +83,6 @@ public class TestFsLimits {
     fsIsReady = true;
   }
 
-  @Test
-  public void testDefaultMaxComponentLength() {
-    int maxComponentLength = conf.getInt(
-        DFSConfigKeys.DFS_NAMENODE_MAX_COMPONENT_LENGTH_KEY,
-        DFSConfigKeys.DFS_NAMENODE_MAX_COMPONENT_LENGTH_DEFAULT);
-    assertEquals(0, maxComponentLength);
-  }
-  
-  @Test
-  public void testDefaultMaxDirItems() {
-    int maxDirItems = conf.getInt(
-        DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY,
-        DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_DEFAULT);
-    assertEquals(0, maxDirItems);
-  }
-
   @Test
   public void testNoLimits() throws Exception {
     addChildWithName("1", null);
@@ -129,6 +114,22 @@ public class TestFsLimits {
     addChildWithName("4444", MaxDirectoryItemsExceededException.class);
   }
 
+  @Test
+  public void testMaxDirItemsLimits() throws Exception {
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY, 0);
+    try {
+      addChildWithName("1", null);
+    } catch (IllegalArgumentException e) {
+      GenericTestUtils.assertExceptionContains("Cannot set dfs", e);
+    }
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_MAX_DIRECTORY_ITEMS_KEY, 64*100*1024);
+    try {
+      addChildWithName("1", null);
+    } catch (IllegalArgumentException e) {
+      GenericTestUtils.assertExceptionContains("Cannot set dfs", e);
+    }
+  }
+
   @Test
   public void testMaxComponentsAndMaxDirItems() throws Exception {
     conf.setInt(DFSConfigKeys.DFS_NAMENODE_MAX_COMPONENT_LENGTH_KEY, 3);