apache/hadoop · error · IllegalArgumentException

is not a valid POST operation.

Error message

{str} is not a valid POST operation.

What it means

PostOpParam parses the 'op' query parameter of WebHDFS/HttpFS POST requests against the Op enum in PostOpParam.java:25-36: APPEND, CONCAT, TRUNCATE, UNSETECPOLICY, UNSETSTORAGEPOLICY, NULL. Matching is case-insensitive (Enum.valueOf after upper-casing); any other string throws this IllegalArgumentException, returned to the client as HTTP 400.

Solutions

1. Use exactly APPEND, CONCAT, TRUNCATE, UNSETECPOLICY or UNSETSTORAGEPOLICY as the op value on POST.
2. Move misplaced ops to the right verb: SETSTORAGEPOLICY/SETECPOLICY are PUT; their UNSET twins are POST.
3. If the request is from the Java client, upgrade hadoop-hdfs-client to match the server — the client emits correct verb/op pairs.
4. Echo the failing URL in your logs to spot template typos immediately.

Example fix

# before
curl -i -X POST "http://nn:9870/webhdfs/v1/f?op=SETSTORAGEPOLICY"
# after
curl -i -X PUT  "http://nn:9870/webhdfs/v1/f?op=SETSTORAGEPOLICY&policyname=HOT"
curl -i -X POST "http://nn:9870/webhdfs/v1/f?op=UNSETSTORAGEPOLICY"

private static final Set<String> POST_OPS = Set.of("APPEND","CONCAT","TRUNCATE","UNSETECPOLICY","UNSETSTORAGEPOLICY");
static String checkedPostOp(String op) {
  String v = op.toUpperCase(Locale.ROOT);
  if (!POST_OPS.contains(v)) throw new IllegalArgumentException("op must be one of " + POST_OPS + ": " + op);
  return v;
}

static boolean isValidPostOp(String op) {
  return op != null && Set.of("APPEND","CONCAT","TRUNCATE","UNSETECPOLICY","UNSETSTORAGEPOLICY").contains(op.toUpperCase(Locale.ROOT));
}

When it happens

Trigger: POST ?op=APPENDFILE (typo); POST ?op=SETSTORAGEPOLICY (a PUT op — must not be POSTed); POST ?op=CONCAT missing valid sources; POST ?op=UNSETECPOLICY on an older Hadoop that lacks EC support; any op from the GET/PUT/DELETE families sent with the POST verb.

Common situations: The storage-policy and EC unset operations moved verb families between docs versions (some examples show PUT); hand-rolled REST clients hard-coding the wrong verb; CONCAT workflows where the sources list is built dynamically and the op string is templated.

Related errors

• is not a valid DELETE operation.
• is not a valid GET operation.
• is not a valid PUT operation.
• Failed to parse " " as a radix- integer.
• Failed to parse " " as a radix- long integer.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/010c708641a2fc3c. Report an issue: GitHub.

Appendix: source

Thrown at hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/resources/PostOpParam.java:92

      return NAME + "=" + this;
    }
  }

  private static final Domain<Op> DOMAIN = new Domain<>(NAME, Op.class);

  /**
   * Constructor.
   * @param str a string representation of the parameter value.
   */
  public PostOpParam(final String str) {
    super(DOMAIN, getOp(str));
  }

  private static Op getOp(String str) {
    try {
      return DOMAIN.parse(str);
    } catch (IllegalArgumentException e) {
      throw new IllegalArgumentException(str + " is not a valid " + Type.POST
          + " operation.");
    }
  }

  @Override
  public String getName() {
    return NAME;
  }
}

View on GitHub (pinned to 2add963021)