apache/cassandra · warning · RuntimeException

Use the -d flag to quiet this error and get the exact…

Error message

Use the -d flag to quiet this error and get the exact throughput in megabits/s

What it means

When printing the default inter-DC stream throughput (Mbit), GetInterDCStreamThroughput refuses to round a fractional value: if throughputInDouble is not a mathematical integer and -d was not passed, it throws this RuntimeException directing the user to -d for the exact value.

Solutions

1. Run `nodetool getinterdcstreamthroughput -d` for the exact double
2. Change the inter-DC stream throughput setting to a whole number
3. Update automation to pass -d

Example fix

// before
nodetool getinterdcstreamthroughput
// after
nodetool getinterdcstreamthroughput -d

nodetool getinterdcstreamthroughput -d

try { run(); } catch (RuntimeException e) { if (e.getMessage().contains("-d flag")) runWithDouble(); }

When it happens

Trigger: Running `nodetool getinterdcstreamthroughput` (no -d) when stream_throughput_outbound_megabits_per_sec (inter-DC variant) is configured as a fraction, e.g. 195.5.

Common situations: Fractional throughput tuning values set in cassandra.yaml; monitoring scripts that invoke the command without -d and crash.

Understand the failure class

Background: "unknown output mode", "invalid value for flag", "expects true/false": fixing invalid flag value errors in CLI tools — this error's family across 24 libraries.

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AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/533d5b76ef4922a4. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/tools/nodetool/GetInterDCStreamThroughput.java:81

        }
        else if (interDCStreamThroughputDoubleMbit)
        {
            throughputInDouble = probe.getInterDCStreamThroughputAsDouble();
            probe.output().out.printf("Current stream throughput: %s%n",
                                      throughputInDouble > 0 ? throughputInDouble + " Mb/s" : "unlimited");
        }
        else
        {
            throughputInDouble = probe.getInterDCStreamThroughputAsDouble();
            throughput = probe.getInterDCStreamThroughput();

            if (throughput <= 0)
                probe.output().out.printf("Current inter-datacenter stream throughput: unlimited%n");
            else if (DoubleMath.isMathematicalInteger(throughputInDouble))
                probe.output().out.printf(throughputInDouble + "Current inter-datacenter stream throughput: %s%n", throughput + " Mb/s");
            else
                throw new RuntimeException("Use the -d flag to quiet this error and get the exact throughput in megabits/s");
        }
    }
}

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