apache/hadoop · error · IOException

Incomplete HDFS URI, no host: {}

Error message

Incomplete HDFS URI, no host: {}

What it means

After the scheme check, the Hdfs (AbstractFileSystem) constructor requires a hostname: URI.getHost() must be non-null or it throws IOException("Incomplete HDFS URI, no host: " + theUri). Authority-less URIs such as hdfs:///path (empty authority) cannot be used with the FileContext-level Hdfs impl — an HA nameservice ID as the host is fine because it is still a host.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/fs/Hdfs.java:88

  /**
   * This constructor has the signature needed by
   * {@link AbstractFileSystem#createFileSystem(URI, Configuration)}
   * 
   * @param theUri which must be that of Hdfs
   * @param conf configuration
   * @throws IOException
   */
  Hdfs(final URI theUri, final Configuration conf) throws IOException, URISyntaxException {
    super(theUri, HdfsConstants.HDFS_URI_SCHEME, true,
        HdfsClientConfigKeys.DFS_NAMENODE_RPC_PORT_DEFAULT);

    if (!theUri.getScheme().equalsIgnoreCase(HdfsConstants.HDFS_URI_SCHEME)) {
      throw new IllegalArgumentException("Passed URI's scheme is not for Hdfs");
    }
    String host = theUri.getHost();
    if (host == null) {
      throw new IOException("Incomplete HDFS URI, no host: " + theUri);
    }

    this.dfs = new DFSClient(theUri, conf, getStatistics());
  }

  @Override
  public int getUriDefaultPort() {
    return HdfsClientConfigKeys.DFS_NAMENODE_RPC_PORT_DEFAULT;
  }

  @Override
  public HdfsDataOutputStream createInternal(Path f,
      EnumSet<CreateFlag> createFlag, FsPermission absolutePermission,
      int bufferSize, short replication, long blockSize, Progressable progress,
      ChecksumOpt checksumOpt, boolean createParent) throws IOException {

    final DFSOutputStream dfsos = dfs.primitiveCreate(getUriPath(f),
      absolutePermission, createFlag, createParent, replication, blockSize,

View on GitHub (pinned to 2add963021)

Solutions

1. Set an explicit authority: hdfs://namenode:8020, or for HA hdfs://<nameservice-id>
2. Fix fs.defaultFS in core-site.xml to include the host or nameservice ID
3. Build URIs programmatically with new URI("hdfs", host, path, null) instead of string concatenation that drops the //host part

Example fix

// before
URI u = URI.create("hdfs:///user/me/in.txt"); // no host
FileContext fc = FileContext.getFileContext(u, conf);

// after
URI u = URI.create("hdfs://nn1.example.com:8020/user/me/in.txt");
FileContext fc = FileContext.getFileContext(u, conf);

URI u = URI.create(defaultFs);
if ("hdfs".equalsIgnoreCase(u.getScheme()) && u.getHost() == null) {
  throw new IllegalArgumentException(
      "fs.defaultFS lacks a host/nameservice: " + defaultFs);
}

static boolean hasHdfsAuthority(URI u) {
  return "hdfs".equalsIgnoreCase(u.getScheme()) && u.getHost() != null;
}

try {
  Hdfs h = (Hdfs) AbstractFileSystem.createFileSystem(u, conf);
} catch (IOException e) {
  if (e.getMessage().startsWith("Incomplete HDFS URI")) {
    // add hdfs://host:port or hdfs://nameservice-id
  }
}

When it happens

Trigger: FileContext.getFileContext(...) / create with a defaultFS or URI of 'hdfs:///' or 'hdfs:///user/x' (no authority); URIs built with URI.create("hdfs:///path") or a port-only authority like 'hdfs://:8020'.

Common situations: fs.defaultFS configured without a host or nameservice; scripts stripping the authority when constructing paths; porting code from the FileSystem API (which resolves the default authority) to FileContext (which requires it in the URI).

Related errors

• Passed URI's scheme is not for Hdfs
• Bad configuration of hadoop.security.key.provider.path at ${
• Uri without authority: {uri}
• Wrong FS: {path}, expected: {this.getUri()}
• No scheme in default FS: ${uri}

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/4ae416becd222137. Report an issue: GitHub.