apache/cassandra · error · IllegalArgumentException

Suboption has been specified more than once

Error message

Suboption  has been specified more than once

What it means

OptionSimple represents a single-valued CLI option; it stores the parsed value in a field and throws if accept() is called again while a value is already set. This guards against specifying the same suboption twice on the command line, which would make the effective value ambiguous.

Solutions

1. Remove the duplicate flag so each suboption appears at most once per invocation.
2. If you intended to override, delete the earlier occurrence rather than adding a second one.
3. Audit wrapper scripts for flags appended by both a defaults block and a user block.
4. If you control the option-group code, check/deduplicate the argument list before feeding it to accept().

Example fix

// before
cassandra-stress write n=1000000 -col n=5 n=10
// after
cassandra-stress write n=1000000 -col n=10

Set<String> seen = new HashSet<>();
for (String arg : args) { String key = arg.contains("=") ? arg.substring(0, arg.indexOf('=')) : arg; if (!seen.add(key)) throw new IllegalArgumentException("duplicate option: " + key); }

try { /* parse args */ } catch (IllegalArgumentException e) { if (e.getMessage().contains("specified more than once")) { /* log which flag is duplicated */ } throw e; }

When it happens

Trigger: Passing the same option flag twice in one cassandra-stress invocation, e.g. '-col n=5 n=10' or specifying an option both in a settings string and again on the command line, so accept(param) runs a second time with value != null.

Common situations: Scripting the stress command and accidentally appending a duplicate flag (a default plus an override); a wrapper concatenating two option lists that both set the same key; copy-pasting a flag inside the same -col/-rate group.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

• CAS is supported only for type 'samerow'
• File '' doesn't exist!
• Invalid compaction strategy:
• Invalid default spec:
• Invalid lookback distribution; max value is

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/c601a30210c31db8. Report an issue: GitHub.

Appendix: source

Thrown at tools/stress/src/org/apache/cassandra/stress/settings/OptionSimple.java:111

        return required;
    }

    public boolean present()
    {
        return value != null || defaultValue != null;
    }

    public String value()
    {
        return value != null ? value : defaultValue;
    }

    public boolean accept(String param)
    {
        if (matchPrefix.matcher(param).lookingAt())
        {
            if (value != null)
                throw new IllegalArgumentException("Suboption " + displayPrefix + " has been specified more than once");
            String v = param.substring(displayPrefix.length());
            value = valueAdapter.apply(v);
            assert value != null;
            return true;
        }
        return false;
    }

    @Override
    public boolean happy()
    {
        return !required || value != null;
    }

    public String shortDisplay()
    {
        StringBuilder sb = new StringBuilder();
        if (!required)

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