apache/cassandra · error · java.lang.IllegalArgumentException

arguments for -F are json,yaml only.

Error message

arguments for -F are json,yaml only.

What it means

TpStats (thread-pool stats) accepts -F/--output-format restricted to exactly 'json' or 'yaml' (or empty for default output). Any other string throws IllegalArgumentException before stats are collected. Same allowlist pattern as TableStats.

Solutions

1. Use -F json or -F yaml exactly (lowercase).
2. Omit -F for the default table output.
3. Convert the JSON/YAML output downstream if another format is required.

Example fix

// before
nodetool tpstats -F csv
// after
nodetool tpstats -F json

if (!outputFormat.isEmpty() && !outputFormat.equals("json") && !outputFormat.equals("yaml"))
    throw new IllegalArgumentException("-F must be json or yaml");

try { runNodetool("tpstats", "-F", fmt); }
catch (IllegalArgumentException e) { if (e.getMessage().contains("-F are json,yaml")) fmt = ""; else throw e; }

When it happens

Trigger: `nodetool tpstats -F csv`, `-F XML`, or any format value other than json/yaml.

Common situations: Copy-pasting format flags from other tools; uppercase format names; expecting csv/tsv support that nodetool does not provide.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• arguments for -F are json,yaml only.
• arguments for -F are json,yaml only.
• argument for sort must be one of
• argument for top must be a positive integer.
• arguments for -F are json, yaml, table only.

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/5fa5b27ba56a1861. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/tools/nodetool/TpStats.java:47

@Command(name = "tpstats", description = "Print usage statistics of thread pools")
public class TpStats extends AbstractCommand
{
    @Option(paramLabel = "format",
            names = { "-F", "--format" },
            description = "Output format (json, yaml)")
    private String outputFormat = "";

    @Option(paramLabel = "verbose",
            names = { "-v", "--verbose" },
            description = "Display detailed metrics about thread pool's sizes")
    private boolean verbose = false;

    @Override
    public void execute(NodeProbe probe)
    {
        if (!outputFormat.isEmpty() && !"json".equals(outputFormat) && !"yaml".equals(outputFormat))
        {
            throw new IllegalArgumentException("arguments for -F are json,yaml only.");
        }

        StatsHolder data = new TpStatsHolder(probe);
        StatsPrinter printer = TpStatsPrinter.from(outputFormat);
        printer.print(data, probe.output().out, verbose);
    }
}

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