What causes "%s must be greater than 0, but was %f" in apache/cassandra?

Set tombstone_threshold to a non-negative float between 0 and 1 (it is a ratio of garbage tombstones), e.g. 0.2.

apache/cassandra · error · ConfigurationException

%s must be greater than 0, but was %f

Error message

%s must be greater than 0, but was %f

What it means

AbstractCompactionStrategy.validateOptions checks the tombstone_threshold option: the parsed float must be >= 0. A negative value throws ConfigurationException '%s must be greater than 0, but was %f'. Note the check rejects only negative values (0 passes despite the message wording).

Source

Thrown at src/java/org/apache/cassandra/db/compaction/AbstractCompactionStrategy.java:461

            long columns = sstable.getEstimatedCellPerPartitionCount().mean() * remainingKeys;
            double remainingColumnsRatio = ((double) columns) / (sstable.getEstimatedCellPerPartitionCount().count() * sstable.getEstimatedCellPerPartitionCount().mean());

            // return if we still expect to have droppable tombstones in rest of columns
            return remainingColumnsRatio * droppableRatio > tombstoneThreshold;
        }
    }

    public static Map<String, String> validateOptions(Map<String, String> options) throws ConfigurationException
    {
        String threshold = options.get(TOMBSTONE_THRESHOLD_OPTION);
        if (threshold != null)
        {
            try
            {
                float thresholdValue = Float.parseFloat(threshold);
                if (thresholdValue < 0)
                {
                    throw new ConfigurationException(String.format("%s must be greater than 0, but was %f", TOMBSTONE_THRESHOLD_OPTION, thresholdValue));
                }
            }
            catch (NumberFormatException e)
            {
                throw new ConfigurationException(String.format("%s is not a parsable int (base10) for %s", threshold, TOMBSTONE_THRESHOLD_OPTION), e);
            }
        }

        String interval = options.get(TOMBSTONE_COMPACTION_INTERVAL_OPTION);
        if (interval != null)
        {
            try
            {
                long tombstoneCompactionInterval = Long.parseLong(interval);
                if (tombstoneCompactionInterval < 0)
                {
                    throw new ConfigurationException(String.format("%s must be greater than 0, but was %d", TOMBSTONE_COMPACTION_INTERVAL_OPTION, tombstoneCompactionInterval));
                }

View on GitHub (pinned to 88fd0f6a0e)

Solutions

Set tombstone_threshold to a non-negative float between 0 and 1 (it is a ratio of garbage tombstones), e.g. 0.2.
Re-run the ALTER TABLE / nodetool table compaction option update with the corrected value.
If you meant a time-based trigger, use tombstone_compaction_interval instead.
Validate options programmatically via compaction strategy validateOptions before applying.

Example fix

// before
ALTER TABLE ks.tbl WITH compaction = {'class': 'SizeTieredCompactionStrategy', 'tombstone_threshold': '-0.5'};
// after
ALTER TABLE ks.tbl WITH compaction = {'class': 'SizeTieredCompactionStrategy', 'tombstone_threshold': '0.2'};

Defensive patterns

Strategy: validation

Validate before calling

float v = Float.parseFloat(opts.getOrDefault("tombstone_threshold", "0.2"));
if (v < 0 || v > 1)
    throw new ConfigurationException("tombstone_threshold must be a ratio in [0,1]");

Try / catch

try {
    strategy.validateOptions(options);
} catch (ConfigurationException e) {
    logger.error("Invalid compaction option: {}", e.getMessage());
}

Prevention

Remember tombstone_threshold is a ratio (0..1), not a time or byte count
Validate compaction options with validateOptions before ALTER TABLE
Use tombstone_compaction_interval for time-based tombstone checks

When it happens

Trigger: ALTER TABLE ... WITH compaction = {'class': '...', 'tombstone_threshold': '-0.1'} or supplying the option in cassandra.yaml/compaction options with a negative float.

Common situations: Sign typo in schema definition; copy-pasted negative values from ratio-style options; scripting that computes a negative threshold; confusion between tombstone_threshold (ratio) and tombstone_compaction_interval (seconds).

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/e1cb77a1e04d446a. Report an issue: GitHub.