apache/hadoop · error · IllegalArgumentException

Leaf nodes are not on the same level

Error message

Leaf nodes are not on the same level

What it means

Error "Leaf nodes are not on the same level" thrown in apache/hadoop.

Source

Thrown at hadoop-tools/hadoop-rumen/src/main/java/org/apache/hadoop/tools/rumen/ZombieCluster.java:105

      MachineNode defaultNode) {
    Map<LoggedNetworkTopology, Integer> levelMapping = 
      new IdentityHashMap<LoggedNetworkTopology, Integer>();
    Deque<LoggedNetworkTopology> unvisited = 
      new ArrayDeque<LoggedNetworkTopology>();
    unvisited.add(topology);
    levelMapping.put(topology, 0);
    
    // building levelMapping and determine leafLevel
    int leafLevel = -1; // -1 means leafLevel unknown.
    for (LoggedNetworkTopology n = unvisited.poll(); n != null; 
      n = unvisited.poll()) {
      int level = levelMapping.get(n);
      List<LoggedNetworkTopology> children = n.getChildren();
      if (children == null || children.isEmpty()) {
        if (leafLevel == -1) {
          leafLevel = level;
        } else if (leafLevel != level) {
          throw new IllegalArgumentException(
              "Leaf nodes are not on the same level");
        }
      } else {
        for (LoggedNetworkTopology child : children) {
          levelMapping.put(child, level + 1);
          unvisited.addFirst(child);
        }
      }
    }

    /**
     * A second-pass dfs traverse of topology tree. path[i] contains the parent
     * of the node at level i+1.
     */
    Node[] path = new Node[leafLevel];
    unvisited.add(topology);
    for (LoggedNetworkTopology n = unvisited.poll(); n != null; 
      n = unvisited.poll()) {

View on GitHub (pinned to 2add963021)

Solutions

1. Check the cluster topology; ZombieCluster requires all leaves at equal depth in the rack/machine tree.

When it happens

Trigger: ZombieCluster is built from a topology whose leaf (machine) nodes sit at different depths, so the cluster tree is malformed.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/276d866cd11a642a. Report an issue: GitHub.