apache/hadoop · error · IOException

Print network topology failed. {}

Error message

Print network topology failed. {}

What it means

Error "Print network topology failed. {}" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NetworkTopologyServlet.java:79

    if (FORMAT_TEXT.equals(format)) {
      response.setContentType("text/plain; charset=UTF-8");
    } else if (FORMAT_JSON.equals(format)) {
      response.setContentType("application/json; charset=UTF-8");
    }

    NameNode nn = NameNodeHttpServer.getNameNodeFromContext(context);
    BlockManager bm = nn.getNamesystem().getBlockManager();
    List<Node> leaves = bm.getDatanodeManager().getNetworkTopology()
        .getLeaves(NodeBase.ROOT);

    try (PrintStream out = new PrintStream(
            response.getOutputStream(), false, "UTF-8")) {
      printTopology(out, leaves, format);
    } catch (Throwable t) {
      String errMsg = "Print network topology failed. "
              + StringUtils.stringifyException(t);
      response.sendError(HttpServletResponse.SC_GONE, errMsg);
      throw new IOException(errMsg);
    } finally {
      response.getOutputStream().close();
    }
  }

  /**
   * Display each rack and the nodes assigned to that rack, as determined
   * by the NameNode, in a hierarchical manner.  The nodes and racks are
   * sorted alphabetically.
   *
   * @param stream print stream
   * @param leaves leaves nodes under base scope
   * @param format the response format
   */
  protected void printTopology(PrintStream stream, List<Node> leaves,
      String format) throws BadFormatException, IOException {
    if (leaves.isEmpty()) {
      stream.print("No DataNodes");

View on GitHub (pinned to 2add963021)

Solutions

1. Check NameNode logs for the topology error detail and verify the network topology (script or table) configuration is valid.

When it happens

Trigger: The /topology or printTopology servlet fails while rendering the cluster network topology.

Common situations: A broken net topology script or dfs.networkscript configuration causing topology resolution failure.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/0caba2fb71623daa. Report an issue: GitHub.