apache/cassandra · error · AssertionError

The sum of nodes in each rack %s must equal total node count

Error message

The sum of nodes in each rack %s must equal total node count %s.

What it means

GenerateTokens.main validates that the per-rack node counts given via -r/-n sum exactly to the total node count given via -t. An AssertionError signals a configuration mismatch between the racks definition and total nodes, so token generation cannot proceed.

Source

Thrown at src/java/org/apache/cassandra/tools/GenerateTokens.java:80

        try
        {
            // disable the summary statistics logging, since this is a command-line tool with dedicated output
            ((Logger) LoggerFactory.getLogger(TokenAllocation.class)).setLevel(Level.ERROR);

            Util.initDatabaseDescriptor();
            options = getOptions();
            CommandLine cmd = parseCommandLine(args, options);

            rf = Integer.parseInt(cmd.getOptionValue(RF));
            tokens = Integer.parseInt(cmd.getOptionValue(TOKENS));
            nodes = Integer.parseInt(cmd.getOptionValue(NODES));
            logger = new OutputHandler.SystemOutput(cmd.hasOption(VERBOSE), true, true);

            partitioner = FBUtilities.newPartitioner(cmd.getOptionValue(PARTITIONER, Murmur3Partitioner.class.getSimpleName()));
            racksDef = getRacks(cmd.getOptionValue(RACKS, cmd.getOptionValue(NODES)));
            if (Arrays.stream(racksDef).sum() != nodes)
            {
                throw new AssertionError(String.format("The sum of nodes in each rack %s must equal total node count %s.",
                                                       cmd.getOptionValue(RACKS),
                                                       cmd.getOptionValue(NODES)));
            }
        }
        catch (NumberFormatException e)
        {
            System.err.println("Invalid integer " + e.getMessage());
            System.out.println();
            printUsage(options);
            System.exit(1);
        }
        catch (AssertionError | ConfigurationException | ParseException t)
        {
            System.err.println(t.getMessage());
            System.out.println();
            printUsage(options);
            System.exit(1);
        }

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Adjust the -r/-n rack counts so they sum to the -t total node count.
2. Recount the cluster's nodes per rack and regenerate the option values.
3. Check the printed values of RACKS/NODES options in the message to spot which side is wrong.

Example fix

// before
// GenerateTokens -t 6 -r 2,2,1 ...
// after
// GenerateTokens -t 6 -r 2,2,2 ...

int sum = Arrays.stream(racksDef).sum();
if (sum != nodes)
    throw new IllegalArgumentException("Rack counts sum " + sum + " != total nodes " + nodes);

try { GenerateTokens.main(args); } catch (AssertionError e) { System.err.println("Fix -r/-n vs -t: " + e.getMessage()); }

When it happens

Trigger: Running GenerateTokens where Arrays.stream(racksDef).sum() != nodes, e.g. -t 6 with -r 2,2,1 (sum 5), or omitting/misspelling one of the options so defaults disagree.

Common situations: Adding a node to the cluster but forgetting to update the racks list; typos in comma-separated counts; confusing -n (nodes per rack list) with -t (total).

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Cannot specify a repair as both paxos only and accord only
• Start and end tokens must be different.
• The specified range %s is not a range that is owned by this
• Tokens must be provided to force join a node.
• When specifying the table for a snapshot, you must specify o

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/378ef22365c44cd9. Report an issue: GitHub.