apache/hadoop · error · IllegalArgumentException

${name}, which is located at ${networkLocation}, is not a de

Error message

${name}, which is located at ${networkLocation}, is not a descendant of ${path}

What it means

IllegalArgumentException from InnerNodeImpl.add(Node) when the node being added is not located under this inner node: n's network location does not begin with this node's path, so it cannot become a child. The message includes the node name, its network location, and the path it was expected to descend from. The check keeps the topology tree consistent — you can only add '/dc1/rack1/node1' to '/dc1/rack1' or its ancestors.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/InnerNodeImpl.java:132

    if (!isAncestor(n)) {
      throw new IllegalArgumentException(
                                         this + "is not an ancestor of " + n);
    }
    String name = n.getNetworkLocation().substring(getPath(this).length());
    if (name.charAt(0) == PATH_SEPARATOR) {
      name = name.substring(1);
    }
    int index=name.indexOf(PATH_SEPARATOR);
    if (index != -1) {
      name = name.substring(0, index);
    }
    return name;
  }

  @Override
  public boolean add(Node n) {
    if (!isAncestor(n)) {
      throw new IllegalArgumentException(n.getName()
          + ", which is located at " + n.getNetworkLocation()
          + ", is not a descendant of " + getPath(this));
    }
    if (isParent(n)) {
      // this node is the parent of n; add n directly
      n.setParent(this);
      n.setLevel(this.level+1);
      Node prev = childrenMap.put(n.getName(), n);
      if (prev != null) {
        for(int i=0; i<children.size(); i++) {
          if (children.get(i).getName().equals(n.getName())) {
            children.set(i, n);
            return false;
          }
        }
      }
      children.add(n);
      numOfLeaves++;

View on GitHub (pinned to 2add963021)

Solutions

1. Before add(), verify isAncestor(n) or use NetworkTopology.add() which locates the correct parent instead of guessing
2. Normalize all network locations in the topology script: leading '/', no trailing '/', same depth everywhere
3. Check that getLeaf/getInner lookups use the same location format that was used at Node registration

Example fix

// before
innerNodeRackA.add(nodeInRackB); // nodeInRackB.getNetworkLocation()=/rackB -> IllegalArgumentException

// after
NetworkTopology clusterTopology = new NetworkTopologyImpl();
clusterTopology.add(nodeInRackB); // routes to the correct parent automatically

if (!innerNode.isAncestor(n)) {
  // do not guess the parent; let NetworkTopology locate it
  topology.add(n);
  return;
}

catch (IllegalArgumentException e) { /* 'not a descendant of' */ log n's location vs expected path; re-resolve parent via getInner/NetworkTopology; }

When it happens

Trigger: Adding a DataNode whose network location is '/rackB' to an InnerNode with path '/rackA'; calling add() on a node obtained by getLeaf while the leaf's location changed; mixing relative ('rack1') and absolute ('/rack1') location strings so the prefix test fails.

Common situations: Topology script returning different racks for the same node over time; DataNodes re-registered with a changed network location; custom Node implementations whose getNetworkLocation() is not normalized.

Related errors

• ${node}is not an ancestor of ${n}
• Wrong length: {digest.length}
• Wrong length: {hex.length}
• Not a hex character: {c}
• No schema options are provided

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/2a91c5c842b7a632. Report an issue: GitHub.