apache/hadoop · error · IOException

Read unexpect number of files: {}

Error message

Read unexpect number of files: {}

What it means

Error "Read unexpect number of files: {}" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java:512

   * @throws IOException
   */  
   private void loadLocalNameINodes(long numFiles, DataInput in, Counter counter)
       throws IOException {
     assert NameNodeLayoutVersion.supports(
         LayoutVersion.Feature.FSIMAGE_NAME_OPTIMIZATION, getLayoutVersion());
     assert numFiles > 0;

     // load root
     loadRoot(in, counter);
     // have loaded the first file (the root)
     numFiles--; 

     // load rest of the nodes directory by directory
     while (numFiles > 0) {
       numFiles -= loadDirectory(in, counter);
     }
     if (numFiles != 0) {
       throw new IOException("Read unexpect number of files: " + -numFiles);
     }
   }
   
    /**
     * Load information about root, and use the information to update the root
     * directory of NameSystem.
     * @param in The {@link DataInput} instance to read.
     * @param counter Counter to increment for namenode startup progress
     */
    private void loadRoot(DataInput in, Counter counter)
        throws IOException {
      // load root
      if (in.readShort() != 0) {
        throw new IOException("First node is not root");
      }
      final INodeDirectory root = loadINode(null, false, in, counter)
        .asDirectory();
      // update the root's attributes

View on GitHub (pinned to 2add963021)

Solutions

1. The fsimage is inconsistent; load from another storage directory or restore from a valid checkpoint.

When it happens

Trigger: Loading an old-format fsimage where the number of files/directories read differs from the count recorded in the image header.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/22b919bb2e7b3d92. Report an issue: GitHub.