apache/hadoop · error · IllegalArgumentException

Missing Operation parameter [{0}]

Error message

Missing Operation parameter [{0}]

What it means

ParametersProvider.get (ParametersProvider.java:68) requires every request to carry the driver query parameter — in HttpFS this is op (HttpFSFileSystem.OP_PARAM = "op"). If request.getParameterMap() contains no 'op' entry, it throws IllegalArgumentException("Missing Operation parameter [op]"), which the WebHDFS endpoint surfaces as HTTP 400.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/wsrs/ParametersProvider.java:68

    try {
      return paramClass.newInstance();
    } catch (Exception ex) {
      throw new UnsupportedOperationException(
        MessageFormat.format("Param class [{0}] does not have default constructor",
            paramClass.getName()));
    }
  }

  public Parameters get(HttpServletRequest request) {
    Map<String, List<Param<?>>> map = new HashMap<>();

    Map<String, String[]> queryString = request.getParameterMap();
    String str = null;
    if(queryString.containsKey(driverParam)) {
      str = queryString.get(driverParam)[0];
    }
    if (str == null) {
      throw new IllegalArgumentException(
        MessageFormat.format("Missing Operation parameter [{0}]",
                             driverParam));
    }
    Enum op;
    try {
      op = Enum.valueOf(enumClass, StringUtils.toUpperCase(str));
    } catch (IllegalArgumentException ex) {
      throw new IllegalArgumentException(
        MessageFormat.format("Invalid Operation [{0}]", str));
    }
    if (!paramsDef.containsKey(op)) {
      throw new IllegalArgumentException(
        MessageFormat.format("Unsupported Operation [{0}]", op));
    }
    for (Class<Param<?>> paramClass : paramsDef.get(op)) {
      Param<?> param = newParam(paramClass);
      List<Param<?>> paramList = Lists.newArrayList();
      String[] ps = queryString.get(param.getName());

View on GitHub (pinned to 2add963021)

Solutions

1. Add the op query parameter with a valid operation name, e.g. &op=GETFILESTATUS.
2. Verify the complete URL (including query string) survives every proxy/gateway hop.
3. Fix or upgrade the client URL builder that omits op.
4. Point liveness probes at a non-WebHDFS endpoint (e.g. /jmx) instead of the WebHDFS API root.

Example fix

# before
curl 'http://nn:14000/webhdfs/v1/user?user.name=hdfs'                 # 400 Missing Operation parameter [op]

# after
curl 'http://nn:14000/webhdfs/v1/user?op=GETFILESTATUS&user.name=hdfs' # 200

String q = uri.getQuery();
if (q == null || !java.util.Arrays.stream(q.split("&")).anyMatch(p -> p.startsWith("op="))) {
  throw new IllegalArgumentException("WebHDFS URL missing required 'op' parameter: " + uri);
}

// server side: register a JAX-RS ExceptionMapper
@Provider
public class IllegalArgumentMapper implements ExceptionMapper<IllegalArgumentException> {
  public Response toResponse(IllegalArgumentException ex) {
    return Response.status(Response.Status.BAD_REQUEST).entity(ex.getMessage()).build();
  }
}

When it happens

Trigger: A request to the httpfs WebHDFS endpoint without an op query component, e.g. curl 'http://host:14000/webhdfs/v1/user?user.name=hdfs'. Also caused by clients whose URL template drops the query string, or proxies/gateways that strip it.

Common situations: Hand-crafted or copy-pasted URLs missing op; a load balancer or rewrite rule dropping query strings; a client library bug after upgrading the WebHDFS URL builder; monitoring probes hitting the API root like a static page.

Understand the failure class

Background: Missing required parameter errors: what 'X is required' and 'the required X param is missing' mean, and how to fix them — this error's family across 27 libraries.

Related errors

• Invalid value [{0}], must be a boolean
• Parameter [{0}], invalid value [{1}], value must be [{2}]
• Invalid Operation [{0}]
• Parameter [{0}], invalid value [{1}], value must be [{2}]
• The length to read ${length} exceeds the file length ${fin.l

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/c3cbcd1bab46e08f. Report an issue: GitHub.