apache/cassandra · error · ConfigurationException

At most bytes may be in a compaction level; your…

Error message

At most %s bytes may be in a compaction level; your maxSSTableSize must be absurdly high to compute %s

What it means

LCS computes the maximum bytes in a level as fanoutSize^(MAX_LEVEL_COUNT-1) * maxSSTableSizeInBytes using BigInteger to avoid silent overflow. If this exceeds Long.MAX_VALUE, the strategy cannot represent level sizes and throws this ConfigurationException, telling the user their maxSSTableSize/fanout combination is absurdly large.

Solutions

Reduce sstable_size_in_mb to a sane value (e.g. 160) and/or keep level_fanout_size at the default 10
ALTER the table with realistic options and re-check
Compute fanout^9 * size_in_bytes offline to verify it fits in a signed 64-bit long before applying

Example fix

// before
{'class':'LeveledCompactionStrategy','sstable_size_in_mb':'10000000','level_fanout_size':'50'}
// after
{'class':'LeveledCompactionStrategy','sstable_size_in_mb':'160','level_fanout_size':'10'}

Defensive patterns

Strategy: validation

Validate before calling

long ssSize = Long.parseLong(opts.getOrDefault("sstable_size_in_mb", "160"));
int fanout = Integer.parseInt(opts.getOrDefault("level_fanout_size", "10"));
if (BigInteger.valueOf(fanout).pow(8).multiply(BigInteger.valueOf(ssSize).multiply(BigInteger.valueOf(1L<<20))).compareTo(BigInteger.valueOf(Long.MAX_VALUE)) > 0)
    throw new IllegalArgumentException("fanout^9 * sstable bytes exceeds Long.MAX_VALUE");

Try / catch

try { execute(alterStmt); }
catch (ConfigurationException e) { if (e.getMessage().startsWith("At most")) { /* shrink sstable_size_in_mb or fanout */ } else throw e; }

Prevention

Compute fanout^(9) * sstableBytes offline before applying extreme tuning
Cap sstable_size_in_mb and level_fanout_size in tooling
Keep LCS options near defaults unless profiling justifies otherwise

When it happens

Trigger: Very large sstable_size_in_mb combined with a large level_fanout_size such that fanout^9 * sstableBytes > 2^63-1 during CREATE/ALTER TABLE or strategy construction.

Common situations: Copy-paste of extreme tuning values (e.g. sstable_size_in_mb of millions); accidental extra digits in config automation.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/970f6f921df4ab65. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/compaction/LeveledCompactionStrategy.java:636

            if (fanoutSize < 1)
            {
                throw new ConfigurationException(String.format("%s must be larger than 0, but was %s", LEVEL_FANOUT_SIZE_OPTION, fanoutSize));
            }
        }
        catch (NumberFormatException ex)
        {
            throw new ConfigurationException(String.format("%s is not a parsable int (base10) for %s", levelFanoutSize, LEVEL_FANOUT_SIZE_OPTION), ex);
        }

        // Validate max Bytes for a level
        try
        {
            long maxSSTableSizeInBytes = Math.multiplyExact(ssSize, 1024L * 1024L); // Convert MB to Bytes
            BigInteger fanoutPower = BigInteger.valueOf(fanoutSize).pow(MAX_LEVEL_COUNT - 1);
            BigInteger maxBytes = fanoutPower.multiply(BigInteger.valueOf(maxSSTableSizeInBytes));
            BigInteger longMaxValue = BigInteger.valueOf(Long.MAX_VALUE);
            if (maxBytes.compareTo(longMaxValue) > 0)
                throw new ConfigurationException(String.format("At most %s bytes may be in a compaction level; " +
                        "your maxSSTableSize must be absurdly high to compute %s", Long.MAX_VALUE, maxBytes));
        }
        catch (ArithmeticException ex)
        {
            throw new ConfigurationException(String.format("sstable_size_in_mb=%d is too large; resulting bytes exceed Long.MAX_VALUE (%d)", ssSize, Long.MAX_VALUE), ex);
        }

        uncheckedOptions.remove(LEVEL_FANOUT_SIZE_OPTION);
        uncheckedOptions.remove(SINGLE_SSTABLE_UPLEVEL_OPTION);

        uncheckedOptions.remove(CompactionParams.Option.MIN_THRESHOLD.toString());
        uncheckedOptions.remove(CompactionParams.Option.MAX_THRESHOLD.toString());

        uncheckedOptions = SizeTieredCompactionStrategyOptions.validateOptions(options, uncheckedOptions);

        return uncheckedOptions;
    }
}

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