apache/hadoop · error · IllegalStateException

Duplicate mapping: {} {} {}

Error message

Duplicate mapping: {} {} {}

What it means

Error "Duplicate mapping: {} {} {}" thrown in apache/hadoop.

Source

Thrown at hadoop-tools/hadoop-fs2img/src/main/java/org/apache/hadoop/hdfs/server/namenode/UGIResolver.java:89

  private final Map<String, Integer> users;
  private final Map<String, Integer> groups;

  public UGIResolver() {
    this(new HashMap<String, Integer>(), new HashMap<String, Integer>());
  }

  UGIResolver(Map<String, Integer> users, Map<String, Integer> groups) {
    this.users = users;
    this.groups = groups;
  }

  public Map<Integer, String> ugiMap() {
    Map<Integer, String> ret = new HashMap<>();
    for (Map<String, Integer> m : Arrays.asList(users, groups)) {
      for (Map.Entry<String, Integer> e : m.entrySet()) {
        String s = ret.put(e.getValue(), e.getKey());
        if (s != null) {
          throw new IllegalStateException("Duplicate mapping: " +
              e.getValue() + " " + s + " " + e.getKey());
        }
      }
    }
    return ret;
  }

  public abstract void addUser(String name);

  protected void addUser(String name, int id) {
    Integer uid = users.put(name, id);
    if (uid != null) {
      throw new IllegalArgumentException("Duplicate mapping: " + name +
          " " + uid + " " + id);
    }
  }

  public abstract void addGroup(String name);

View on GitHub (pinned to 2add963021)

Solutions

1. Remove the duplicate user/group mapping entry from the UGI mapping input so each name maps once.

When it happens

Trigger: Two different user or group names map to the same numeric id in UGIResolver, so the fsimage would contain an ambiguous mapping; the input mapping data is inconsistent.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/0fe6e31d82d662ed. Report an issue: GitHub.