apache/cassandra · error · IllegalArgumentException

Invalid parameter list for extreme (Weibull) distribution:

Error message

Invalid parameter list for extreme (Weibull) distribution:

What it means

ExtremeImpl.getFactory() parses EXTREME(min..max,shape) specs (Weibull distribution) and throws IllegalArgumentException when the parameter list does not contain exactly 2 entries. Both the range and the shape parameter are required.

Source

Thrown at tools/stress/src/org/apache/cassandra/stress/settings/OptionDistribution.java:279

                ExponentialDistribution findBounds = new ExponentialDistribution(1d);
                // max probability should be roughly equal to accuracy of (max-min) to ensure all values are visitable,
                // over entire range, but this results in overly skewed distribution, so take sqrt
                final double mean = (max - min) / findBounds.inverseCumulativeProbability(1d - Math.sqrt(1d/(max-min)));
                return new ExpFactory(min, max, mean);
            } catch (Exception ignore)
            {
                throw new IllegalArgumentException("Invalid parameter list for uniform distribution: " + params);
            }
        }
    }

    private static final class ExtremeImpl implements Impl
    {
        @Override
        public DistributionFactory getFactory(List<String> params)
        {
            if (params.size() != 2)
                throw new IllegalArgumentException("Invalid parameter list for extreme (Weibull) distribution: " + params);
            try
            {
                String[] bounds = params.get(0).split("\\.\\.+");
                final long min = parseLong(bounds[0]);
                final long max = parseLong(bounds[1]);
                if (min == max)
                    return new FixedFactory(min);
                final double shape = Double.parseDouble(params.get(1));
                WeibullDistribution findBounds = new WeibullDistribution(shape, 1d);
                // max probability should be roughly equal to accuracy of (max-min) to ensure all values are visitable,
                // over entire range, but this results in overly skewed distribution, so take sqrt
                final double scale = (max - min) / findBounds.inverseCumulativeProbability(1d - Math.sqrt(1d/(max-min)));
                return new ExtremeFactory(min, max, shape, scale);
            } catch (Exception ignore)
            {
                throw new IllegalArgumentException("Invalid parameter list for extreme (Weibull) distribution: " + params);
            }
        }

View on GitHub (pinned to 88fd0f6a0e)

Solutions

Supply exactly two parameters: EXTREME(min..max,shape), e.g. EXTREME(1..1000,2.5).
If you only want a range, use UNIFORM(min..max) or EXP(min..max) instead.
If you intended the quantized variant, use QEXTREME(min..max,shape,quantas) with 3 parameters.

Example fix

// before
EXTREME(1..1000)
// after
EXTREME(1..1000, 2.5)

Defensive patterns

Strategy: validation

Validate before calling

List<String> params = ...; // from EXTREME(...)
if (params.size() != 2)
    throw new IllegalArgumentException("EXTREME expects exactly 2 params min..max,shape, got " + params);
Double.parseDouble(params.get(1)); // shape must be numeric

Try / catch

try {
    DistributionFactory f = extremeImpl.getFactory(params);
} catch (IllegalArgumentException e) {
    System.err.println("EXTREME requires (min..max, shape): " + e.getMessage());
}

Prevention

Always include the Weibull shape parameter with EXTREME/extr/weibull.
Use QEXTREME with 3 params only when quantization is intended.
Validate arity before invoking getFactory in generated profiles.

When it happens

Trigger: Calling getFactory with 1 parameter ('extr(1..1000)' missing the shape) or 3+ parameters ('extr(1..1000,2,3)'), including empty trailing-comma arguments.

Common situations: Users omitting the required Weibull shape argument because UNIFORM/EXP only need a range, or copying QEXTREME syntax (which takes 3 params) but invoking the plain EXTREME alias.

Understand the failure class

Background: "Unknown argument", "Invalid value", and "must be one of": invalid CLI argument errors explained — this error's family across 35 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/53ef724d764473f7. Report an issue: GitHub.