What causes "value cannot be blank" in apache/hadoop?

Set a valid default with unit for the config key, e.g. conf.get(key, "128MB")

apache/hadoop · error · IllegalStateException

value cannot be blank

Error message

value cannot be blank

What it means

StorageSize.parse(String) converts a size literal like "1000MB" into a StorageUnit + double pair. Its first step is checkState(isNotBlank(value), "value cannot be blank"), so null, empty, or whitespace-only input fails immediately. Note the exception type is IllegalStateException (the checkState helper throws ISE), not IllegalArgumentException as for later format problems.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/StorageSize.java:46

public class StorageSize {
  private final StorageUnit unit;
  private final double value;

  /**
   * Constucts a Storage Measure, which contains the value and the unit of
   * measure.
   *
   * @param unit - Unit of Measure
   * @param value - Numeric value.
   */
  public StorageSize(StorageUnit unit, double value) {
    this.unit = unit;
    this.value = value;
  }

  private static void checkState(boolean state, String errorString){
    if(!state) {
      throw new IllegalStateException(errorString);
    }
  }

  public static StorageSize parse(String value) {
    checkState(isNotBlank(value), "value cannot be blank");
    String sanitizedValue = value.trim().toLowerCase(Locale.ENGLISH);
    StorageUnit parsedUnit = null;
    for (StorageUnit unit : StorageUnit.values()) {
      if (sanitizedValue.endsWith(unit.getShortName()) ||
          sanitizedValue.endsWith(unit.getLongName()) ||
          sanitizedValue.endsWith(unit.getSuffixChar())) {
        parsedUnit = unit;
        break;
      }
    }

    if (parsedUnit == null) {
      throw new IllegalArgumentException(value + " is not in expected format." +

View on GitHub (pinned to 2add963021)

Solutions

Set a valid default with unit for the config key, e.g. conf.get(key, "128MB")
Null/blank-check the string before calling StorageSize.parse() and fail with a message naming the key
Fix the property name or the substitution expression so it cannot resolve to null/empty

Example fix

// before
StorageSize size = StorageSize.parse(conf.get("some.size.key")); // ISE if unset

// after
String raw = conf.get("some.size.key", "128MB");
if (StringUtils.isBlank(raw)) {
  throw new IllegalArgumentException("some.size.key must be set, e.g. 128MB");
}
StorageSize size = StorageSize.parse(raw);

Defensive patterns

Strategy: validation

Validate before calling

String raw = conf.get(key, defaultWithUnit); // e.g. default "128MB"
if (StringUtils.isBlank(raw)) {
  throw new IllegalArgumentException(key + " must be a non-empty <number><unit> value");
}
StorageSize size = StorageSize.parse(raw);

Try / catch

try {
  size = StorageSize.parse(raw);
} catch (IllegalStateException e) {
  // blank input -> fail with the config key name for actionable context
  throw new IllegalArgumentException(key + " is unset/empty; expected e.g. 128MB", e);
}

Prevention

Always supply a unit-bearing default when reading size-typed config keys
Add config sanity checks at service startup rather than at first use
Lint configs for empty <value/> elements in CI

When it happens

Trigger: StorageSize.parse(null), parse(""), or parse(" "); almost always the argument came straight from an unset or empty configuration property (conf.get(key) returning null or an empty string).

Common situations: A newly introduced size-typed config key with no default in the XML; a property defined with an empty <value/>; variable substitution (${...}) resolving to empty; a typo'd key name making conf.get() return null.

Related errors

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/c48d4e1322dbe40a. Report an issue: GitHub.