apache/hadoop · error · IllegalArgumentException

Illegal minload factor: {}

Error message

Illegal minload factor: {}

What it means

The second constructor validation in LightWeightHashSet: minLoadFactor must satisfy 0 < minLoadFactor <= maxLoadFactor, since it computes the shrink threshold below which the bucket array is contracted. Violating the ordering (min > max) or using a non-positive min throws IllegalArgumentException immediately.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/LightWeightHashSet.java:117

  /**
   * @param initCapacity
   *          Recommended size of the internal array.
   * @param maxLoadFactor
   *          used to determine when to expand the internal array
   * @param minLoadFactor
   *          used to determine when to shrink the internal array
   */
  @SuppressWarnings("unchecked")
  public LightWeightHashSet(int initCapacity, float maxLoadFactor,
      float minLoadFactor) {

    if (maxLoadFactor <= 0 || maxLoadFactor > 1.0f)
      throw new IllegalArgumentException("Illegal maxload factor: "
          + maxLoadFactor);

    if (minLoadFactor <= 0 || minLoadFactor > maxLoadFactor)
      throw new IllegalArgumentException("Illegal minload factor: "
          + minLoadFactor);

    this.initialCapacity = computeCapacity(initCapacity);
    this.capacity = this.initialCapacity;
    this.hash_mask = capacity - 1;

    this.maxLoadFactor = maxLoadFactor;
    this.expandThreshold = (int) (capacity * maxLoadFactor);
    this.minLoadFactor = minLoadFactor;
    this.shrinkThreshold = (int) (capacity * minLoadFactor);

    entries = new LinkedElement[capacity];
    if (LOG.isDebugEnabled()) {
      LOG.debug("initial capacity=" + initialCapacity + ", max load factor= "
          + maxLoadFactor + ", min load factor= " + minLoadFactor);
    }
  }

View on GitHub (pinned to 2add963021)

Solutions

1. Order the arguments correctly and keep min within (0, max]; defaults are DEFAULT_MAX_LOAD_FACTOR = 0.75f and DEFAUT_MIN_LOAD_FACTOR = 0.2f.
2. Name intermediate variables (float maxLoadFactor, float minLoadFactor) at the call site so swaps are visible in review.
3. Range-check both factors at the boundary where external config enters the code.

Example fix

// before
new LightWeightHashSet<>(16, 0.2f, 0.75f); // min > max -> IllegalArgumentException

// after
float maxLoadFactor = 0.75f;
float minLoadFactor = 0.2f; // must satisfy 0 < min <= max
new LightWeightHashSet<>(16, maxLoadFactor, minLoadFactor);

static boolean isValidMinLoadFactor(float min, float max) {
  return min > 0f && min <= max;
}
// before constructing:
if (!isValidMinLoadFactor(min, max)) throw new IllegalArgumentException("min must be in (0,max]: " + min + ", max=" + max);

static boolean isValidMinLoadFactor(float min, float max) { return min > 0f && min <= max; }

When it happens

Trigger: The 3-arg constructor with minLoadFactor <= 0, or minLoadFactor > maxLoadFactor - e.g., (16, 0.25f, 0.5f) or (16, 0.75f, 2.0f). Frequently the result of swapped 2nd/3rd arguments.

Common situations: Argument-order mistakes when hand-writing the constructor call; percentages again (min 20 with max 0.75f); refactors that changed parameter order between versions of internal wrappers.

Related errors

• Illegal maxload factor: {}
• Path must be absolute: " + path
• Copy destination must be different from source for %s.
• Block size must be greater than 0
• Replication must be greater than 0

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/2299b063438ac5d5. Report an issue: GitHub.