apache/cassandra · error · ConfigurationException

Token allocation does not support replication strategy

Error message

Token allocation does not support replication strategy 

What it means

TokenAllocation only supports NetworkTopologyStrategy and SimpleStrategy replication strategies. When createStrategy encounters any other strategy (e.g. LocalStrategy or a custom IReplicationStrategy subclass) it throws ConfigurationException because no StrategyAdapter can be produced for computing allocation weights.

Solutions

1. Use a supported strategy (SimpleStrategy or NetworkTopologyStrategy) on the keyspace being allocated for
2. If you need allocation for a custom strategy, implement a corresponding StrategyAdapter in TokenAllocation
3. Target a different keyspace when invoking token allocation
4. Check the keyspace's strategy via cqlsh: DESCRIBE KEYSPACE

Example fix

// before
cqlsh> ALTER KEYSPACE myks WITH replication = {'class':'MyCustomStrategy','replication_factor':3};
// token allocation fails
// after
cqlsh> ALTER KEYSPACE myks WITH replication = {'class':'NetworkTopologyStrategy','dc1':3};

// before allocation, check the strategy
String cls = Keyspace.open(ks).getReplicationStrategy().getClass().getSimpleName();
if (!cls.equals("NetworkTopologyStrategy") && !cls.equals("SimpleStrategy"))
    throw new IllegalArgumentException("Unsupported strategy for token allocation: " + cls);

try {
    TokenAllocation.allocate(metadata, ks, dc);
} catch (ConfigurationException e) {
    if (e.getMessage().contains("does not support replication strategy")) {
        // switch keyspace to NetworkTopologyStrategy or pick another keyspace
    }
}

When it happens

Trigger: Calling TokenAllocation.allocate (via createStrategy/getOrCreateStrategy) for a keyspace whose replication strategy is neither NetworkTopologyStrategy nor SimpleStrategy.

Common situations: Trying to allocate tokens for a keyspace using LocalStrategy (system keyspaces) or a third-party custom replication strategy.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

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AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/feafa8cde0f73785. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/dht/tokenallocator/TokenAllocation.java:260

    private StrategyAdapter getOrCreateStrategy(InetAddressAndPort endpoint)
    {
        Location location = metadata.locator.location(endpoint);
        return getOrCreateStrategy(location.datacenter, location.rack);
    }

    private StrategyAdapter getOrCreateStrategy(String dc, String rack)
    {
        return strategyByRackDc.computeIfAbsent(dc, k -> new HashMap<>()).computeIfAbsent(rack, k -> createStrategy(dc, rack));
    }

    private StrategyAdapter createStrategy(String dc, String rack)
    {
        if (replicationStrategy instanceof NetworkTopologyStrategy)
            return createStrategy(metadata, (NetworkTopologyStrategy) replicationStrategy, dc, rack);
        if (replicationStrategy instanceof SimpleStrategy)
            return createStrategy(metadata, (SimpleStrategy) replicationStrategy);
        throw new ConfigurationException("Token allocation does not support replication strategy " + replicationStrategy.getClass().getSimpleName());
    }

    private StrategyAdapter createStrategy(ClusterMetadata metadata, final SimpleStrategy rs)
    {
        return createStrategy(() -> metadata.locator, null, null, rs.getReplicationFactor().allReplicas, false);
    }

    private StrategyAdapter createStrategy(ClusterMetadata metadata, NetworkTopologyStrategy strategy, String dc, String rack)
    {
        int replicas = strategy.getReplicationFactor(dc).allReplicas;

        // if topology hasn't been setup yet for this dc+rack then treat it as a separate unit
        Multimap<String, InetAddressAndPort> datacenterRacks = metadata.directory.datacenterRacks(dc);
        Supplier<Locator> locator = () -> metadata.locator;
        int racks = datacenterRacks != null && datacenterRacks.containsKey(rack)
                ? datacenterRacks.asMap().size()
                : 1;

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