apache/hadoop · critical · IllegalArgumentException

callqueue.capacity.weights only takes positive weights. ${w}

Q: What causes "callqueue.capacity.weights only takes positive weights. ${w} capacity weight found" in apache/hadoop?

Use only positive integers, e.g., '4,3,2,1' — weight a rarely used level with 1 instead of 0.

Error message

callqueue.capacity.weights only takes positive weights. ${w} capacity weight found

What it means

After parseCapacityWeights confirms the count matches the priority levels, it validates each element of ipc.<port>.callqueue.capacity.weights. Any weight <= 0 throws this IllegalArgumentException, because a zero or negative subqueue capacity would make that priority level unusable.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/CallQueueManager.java:432

   * Read the weights of capacity in callqueue and pass the value to
   * callqueue constructions.
   */
  private static int[] parseCapacityWeights(
      int priorityLevels, String ns, Configuration conf) {
    int[] weights = conf.getInts(ns + "." +
      CommonConfigurationKeys.IPC_CALLQUEUE_CAPACITY_WEIGHTS_KEY);
    if (weights.length == 0) {
      weights = getDefaultQueueCapacityWeights(priorityLevels);
    } else if (weights.length != priorityLevels) {
      throw new IllegalArgumentException(
          CommonConfigurationKeys.IPC_CALLQUEUE_CAPACITY_WEIGHTS_KEY + " must "
              + "specify " + priorityLevels + " capacity weights: one for each "
              + "priority level");
    } else {
      // only allow positive numbers
      for (int w : weights) {
        if (w <= 0) {
          throw new IllegalArgumentException(
              CommonConfigurationKeys.IPC_CALLQUEUE_CAPACITY_WEIGHTS_KEY +
                  " only takes positive weights. " + w + " capacity weight " +
                  "found");
        }
      }
    }
    return weights;
  }

  /**
   * By default, queue capacity is the same for all priority levels.
   *
   * @param priorityLevels number of levels
   * @return default weights
   */
  public static int[] getDefaultQueueCapacityWeights(int priorityLevels) {
    int[] weights = new int[priorityLevels];
    Arrays.fill(weights, 1);

View on GitHub (pinned to 2add963021)

Solutions

Use only positive integers, e.g., '4,3,2,1' — weight a rarely used level with 1 instead of 0.
To effectively reduce levels, lower ipc.<port>.scheduler.priority.levels and provide that many positive weights.
Lint the property programmatically before server start (see validation snippet).
Restart the RPC server after correcting core-site.xml.

Example fix

# before
<property><name>ipc.8020.callqueue.capacity.weights</name><value>4,3,2,0</value></property> <!-- 0 is illegal -->

# after
<property><name>ipc.8020.callqueue.capacity.weights</name><value>4,3,2,1</value></property>

Defensive patterns

Strategy: validation

Validate before calling

int[] weights = conf.getInts("ipc.8020.callqueue.capacity.weights");
for (int w : weights) {
  Preconditions.checkArgument(w > 0, "weights must be positive, got %s", w);
}

Prevention

Never use 0 to disable a level; reduce scheduler.priority.levels instead.
Use weight 1 as the minimum for rarely used tiers.
Lint ipc.<port>.callqueue.capacity.weights in deployment pipelines.

When it happens

Trigger: Including 0 (to 'switch off' a level) or a negative number in ipc.<port>.callqueue.capacity.weights; using '-' separators or malformed values that Configuration.getInts parses as negative; hand-edited XML with a stray '-1'.

Common situations: Attempting to disable a FairCallQueue tier by weighting it 0; copy-paste arithmetic in config templates producing negative deltas; operators assuming 0-weight is a legal way to drop a queue level.

Related errors

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/8d1fdff1b3850fbe. Report an issue: GitHub.