apache/cassandra · error · ConfigurationException

Fast path strategy must either be 'keyspace', 'simple'…

Error message

Fast path strategy must either be 'keyspace', 'simple', 'up' or a map size and optional dcs {'size':n, 'dcs': dc0,dc1...

What it means

Parses the accord.fast_path table strategy string from configuration. Only 'keyspace', 'simple', 'up', or a JSON-ish map form {'size':n,'dcs':...} is accepted; any other string raises a ConfigurationException at strategy parsing time. This fails fast on invalid config so the cluster does not start with an unusable fast-path policy.

Solutions

Set the strategy to one of: keyspace, simple, up, or a well-formed {'size':n,'dcs':dc0,dc1...} string.
Check spelling and remove stray whitespace or quotes introduced by YAML.
Validate the config with a startup dry-run after editing cassandra.yaml.

Example fix

// before (cassandra.yaml)
accord:
  fast_path:
    table_strategy: 'KeySpace '
// after
accord:
  fast_path:
    table_strategy: keyspace

Defensive patterns

Strategy: validation

Validate before calling

String s = value.trim().toLowerCase();
boolean ok = s.equals("keyspace") || s.equals("simple") || s.equals("up")
    || s.matches("\\{'size'\\s*:\\s*\\d+\\s*(,\\s*'dcs'\\s*:\\s*[^}]+)?\\}");
if (!ok) throw new ConfigurationException("Invalid fast_path table strategy: " + value);

Try / catch

try {
    FastPathStrategy strategy = FastPathStrategy.tableStrategyFromString(raw);
} catch (ConfigurationException e) {
    logger.error("Bad accord.fast_path config; falling back to default", e);
    strategy = FastPathStrategy.simple();
}

Prevention

Validate cassandra.yaml fast_path settings on config load
Avoid quotes/whitespace mangling in YAML string values
Copy only documented strategy strings
Test config changes in a staging cluster first

When it happens

Trigger: Calling tableStrategyFromString with a string that matches none of 'keyspace', 'simple', 'up', nor a valid map spec — typically a typo like 'KeySpace' with different casing/handling, or a malformed map string.

Common situations: Typo in cassandra.yaml accord.fast_path setting; quoting/escaping issues in YAML mangling the map syntax; copy-pasting a keyspace-allowed keyword that the table strategy parser does not accept.

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

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/1e8bd681f1de31a0. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/service/accord/topology/FastPathStrategy.java:136

                return inheritKeyspace();
            case UP:
                return up();
            default:
                throw new IllegalArgumentException("Unhandled strategy kind: " + kind);
        }
    }

    static FastPathStrategy tableStrategyFromString(String s)
    {
        s = toLowerCaseLocalized(s).trim();
        if (s.equals("keyspace"))
            return InheritKeyspaceFastPathStrategy.instance;
        if (s.equals("simple"))
            return SimpleFastPathStrategy.instance;
        if (s.equals("up"))
            return UpFastPathStrategy.instance;

        throw new ConfigurationException("Fast path strategy must either be 'keyspace', 'simple', 'up' or a map size and optional dcs {'size':n, 'dcs': dc0,dc1...");
    }

    static FastPathStrategy keyspaceStrategyFromString(String s)
    {
        s = toLowerCaseLocalized(s).trim();
        if (s.equals("simple"))
            return SimpleFastPathStrategy.instance;
        if (s.equals("up"))
            return UpFastPathStrategy.instance;

        throw new ConfigurationException("Fast path strategy must either be 'simple', 'up' or a map size and optional dcs {'size':n, 'dcs': dc0,dc1...");
    }

    static FastPathStrategy simple()
    {
        return SimpleFastPathStrategy.instance;
    }

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