apache/hadoop · error · IllegalArgumentException

Invalid value for webhdfs parameter "op"

Error message

Invalid value for webhdfs parameter "op"

What it means

The op parameter value is not one of the six read-only operations FSImageHandler implements (GETFILESTATUS, LISTSTATUS, GETACLSTATUS, GETXATTRS, LISTXATTRS, GETCONTENTSUMMARY); the default branch of the switch throws this IllegalArgumentException, which becomes HTTP 400. The fsimage is a static snapshot, so any op needing live NameNode state or write access is inherently unsupported here.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageHandler.java:119

    case "LISTSTATUS":
      content = image.listStatus(path);
      break;
    case "GETACLSTATUS":
      content = image.getAclStatus(path);
      break;
    case "GETXATTRS":
      List<String> names = getXattrNames(decoder);
      String encoder = getEncoder(decoder);
      content = image.getXAttrs(path, names, encoder);
      break;
    case "LISTXATTRS":
      content = image.listXAttrs(path);
      break;
    case "GETCONTENTSUMMARY":
      content = image.getContentSummary(path);
      break;
    default:
      throw new IllegalArgumentException("Invalid value for webhdfs parameter"
          + " \"op\"");
    }

    LOG.info("op=" + op + " target=" + path);

    DefaultFullHttpResponse resp = new DefaultFullHttpResponse(HTTP_1_1,
        HttpResponseStatus.OK, Unpooled.wrappedBuffer(content
            .getBytes(StandardCharsets.UTF_8)));
    resp.headers().set(CONTENT_TYPE, APPLICATION_JSON_UTF8);
    resp.headers().set(CONTENT_LENGTH, resp.content().readableBytes());
    resp.headers().set(CONNECTION, CLOSE);
    ctx.write(resp).addListener(ChannelFutureListener.CLOSE);
  }

  @Override
  public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
    ctx.flush();
  }

View on GitHub (pinned to 2add963021)

Solutions

1. Switch to one of the supported read-only ops: GETFILESTATUS, LISTSTATUS, GETACLSTATUS, GETXATTRS, LISTXATTRS, GETCONTENTSUMMARY.
2. For file contents or writes, target the live cluster's WebHDFS, not the fsimage viewer.
3. If a newer oiv build supports more read-only ops, upgrade the tooling Hadoop version.

Example fix

# before
curl 'http://localhost:5978/webhdfs/v1/user/foo?op=OPEN'
# -> 400 Invalid value for webhdfs parameter "op"

# after
curl 'http://localhost:5978/webhdfs/v1/user/foo?op=GETFILESTATUS'

private static final Set<String> SUPPORTED_OPS = new HashSet<>(Arrays.asList(
    "GETFILESTATUS", "LISTSTATUS", "GETACLSTATUS",
    "GETXATTRS", "LISTXATTRS", "GETCONTENTSUMMARY"));

String op = params.get("op");
if (op == null || !SUPPORTED_OPS.contains(op.toUpperCase(Locale.ROOT))) {
  throw new IllegalArgumentException("Unsupported op " + op + "; supported: " + SUPPORTED_OPS);
}

static boolean isSupportedOp(String op) {
  return op != null && Arrays.asList("GETFILESTATUS", "LISTSTATUS",
      "GETACLSTATUS", "GETXATTRS", "LISTXATTRS", "GETCONTENTSUMMARY")
      .contains(op.toUpperCase(Locale.ROOT));
}

// server side already maps this to HTTP 400 with a JSON RemoteException
// client side: branch on op before calling the read-only viewer
if (!isSupportedOp(requestedOp)) { useLiveWebHdfsInstead(requestedOp); }

When it happens

Trigger: Calling with op=OPEN (file contents are not stored in the image), write ops like op=MKDIRS/op=DELETE/op=SETPERMISSION, or a mis-typed value like op=GETFILESTATUS2 (values are upper-cased before the switch, so letter case itself is not the issue).

Common situations: Pointing an existing WebHDFS application or script at the offline viewer assuming full API parity; ops introduced in newer WebHDFS versions; configs reused between the live cluster and the viewer.

Related errors

• Param op must be specified.
• Path: {path} should start with /webhdfs/v1
• Storage policy name is empty.
• {} is not supported
• {} is not supported

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/e73171b68e6a2266. Report an issue: GitHub.