apache/hadoop · error · IOException

JSON parser error, {0}

Error message

JSON parser error, {0}

What it means

HttpFSFileSystem.createXAttrNames() parses the server's getXAttrs response (a JSON array of xattr names) with json-simple after the content-type check in HttpFSUtils.jsonParse has already passed. A ParseException is wrapped into IOException("JSON parser error, " + cause), so this specific message means the body claimed to be JSON but failed to parse as the expected structure. It indicates a malformed or structurally different server response, not a bad client call.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/fs/http/client/HttpFSFileSystem.java:1403

      xAttrs.put(name, value);
    }

    return xAttrs;
  }

  /** Convert xAttr names json to names list */
  private List<String> createXAttrNames(String xattrNamesStr) throws IOException {
    JSONParser parser = new JSONParser();
    JSONArray jsonArray;
    try {
      jsonArray = (JSONArray)parser.parse(xattrNamesStr);
      List<String> names = Lists.newArrayListWithCapacity(jsonArray.size());
      for (Object name : jsonArray) {
        names.add((String) name);
      }
      return names;
    } catch (ParseException e) {
      throw new IOException("JSON parser error, " + e.getMessage(), e);
    }
  }

  @Override
  public Map<String, byte[]> getXAttrs(Path f) throws IOException {
    Map<String, String> params = new HashMap<String, String>();
    params.put(OP_PARAM, Operation.GETXATTRS.toString());
    HttpURLConnection conn = getConnection(Operation.GETXATTRS.getMethod(),
        params, f, true);
    HttpExceptionUtils.validateResponse(conn, HttpURLConnection.HTTP_OK);
    JSONObject json = (JSONObject) HttpFSUtils.jsonParse(conn);
    return createXAttrMap((JSONArray) json.get(XATTRS_JSON));
  }

  @Override
  public Map<String, byte[]> getXAttrs(Path f, List<String> names)
      throws IOException {
    Preconditions.checkArgument(names != null && !names.isEmpty(), 

View on GitHub (pinned to 2add963021)

Solutions

1. Inspect the raw response: curl -i 'http://host:14000/webhdfs/v1/<path>?op=GETXATTRS&user.name=...' and confirm it is a valid JSON array
2. Match client hadoop-hdfs-httpfs version to the server version to eliminate protocol/serialization drift
3. Remove or fix any proxy/filter that mutates response bodies on the HttpFS path
4. If the body is valid JSON but not an array, check the server log for the executor that produced it and report a server bug

try {
  Map<String, byte[]> x = fs.getXAttrs(path);
} catch (IOException e) {
  if (e.getMessage() != null && e.getMessage().startsWith("JSON parser error")) {
    // server sent malformed xattr JSON: capture raw response with curl and compare client/server versions
    LOG.error("Malformed GETXATTRS response for {}", path, e);
  }
  throw e;
}

When it happens

Trigger: fs.getXAttrs(path) or fs.getXAttrs(path, names) where the HttpFS server returns a corrupted body, a proxy truncates the stream, or a server version serializes the xattr-names array in a shape the client jar's parser rejects (e.g., object instead of array, which surfaces as a parse failure inside the loop cast).

Common situations: Client/server Hadoop version skew (2.x client against 3.x server or vice versa); an intermediary rewriting response bodies; a server-side bug in xattr JSON serialization after an upgrade.

Related errors

• JSON parser error, {0}
• Attribute with name {} is not found.
• Attributes with name {} are not found.
• XAttr: {} already exists. The REPLACE flag must be specified
• XAttr: {} does not exist. The CREATE flag must be specified.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/5bdcb074b07e4881. Report an issue: GitHub.