apache/cassandra · error · IllegalArgumentException

Unsupported snitch

Error message

Unsupported snitch 

What it means

Accord's topology code requires the configured snitch's NodeProximity to support comparing nodes by endpoint (supportCompareByEndpoint()). If it does not, AccordTopologySorter.checkSnitchSupported throws IllegalArgumentException; a DynamicEndpointSnitch is unwrapped to its delegate first, so the offending snitch class is reported. This guards against snitches that cannot provide the ordering Accord relies on.

Solutions

1. Switch endpoint_snitch to a supported snitch whose NodeProximity.supportCompareByEndpoint() returns true (e.g. SimpleSnitch, NetworkTopologyStrategy-based default snitches).
2. If using a custom snitch, implement supportCompareByEndpoint()/compare-by-endpoint in its NodeProximity implementation.
3. If using DynamicEndpointSnitch, verify its delegate snitch is supported, since the delegate is the one checked/reported.

Example fix

// before (cassandra.yaml)
endpoint_snitch: MyCustomSnitch
// after
endpoint_snitch: SimpleSnitch

// before startup
NodeProximity p = ...;
if (p instanceof DynamicEndpointSnitch) p = ((DynamicEndpointSnitch) p).delegate;
if (!p.supportCompareByEndpoint()) throw new IllegalStateException("Snitch " + p.getClass() + " unsupported for Accord");

boolean isAccordCompatibleSnitch(NodeProximity p) { return p.supportCompareByEndpoint(); }

When it happens

Trigger: Setting a snitch (e.g. via endpoint_snitch in cassandra.yaml or SNITCH env) whose NodeProximity implementation returns false from supportCompareByEndpoint() and then starting Accord/AccordService, which calls checkSnitchSupported during topology construction.

Common situations: Operators switch to a custom or cloud snitch that lacks compare-by-endpoint support; upgrading Cassandra with Accord enabled while keeping an unsupported snitch; wrapping snitches (like DynamicEndpointSnitch) around a delegate that itself is unsupported.

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AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/9223b6fb74a7b6ef. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/service/accord/api/AccordTopologySorter.java:93

        }
    }

    private final AccordEndpointMapper mapper;
    private final Comparator<Endpoint> comparator;

    private AccordTopologySorter(AccordEndpointMapper mapper, Comparator<Endpoint> comparator)
    {
        this.mapper = mapper;
        this.comparator = comparator;
    }

    public static void checkSnitchSupported(NodeProximity proximity)
    {
        if (!proximity.supportCompareByEndpoint())
        {
            if (proximity instanceof DynamicEndpointSnitch)
                proximity = ((DynamicEndpointSnitch) proximity).delegate;
            throw new IllegalArgumentException("Unsupported snitch " + proximity.getClass() + "; supportCompareByEndpoint returned false");
        }
    }

    @Override
    public int compare(Node.Id node1, Node.Id node2, ShardSelection shards)
    {
        InetAddressAndPort ep1 = mapper.mappedEndpointOrNull(node1);
        InetAddressAndPort ep2 = mapper.mappedEndpointOrNull(node2);
        return compare(comparator, ep1, ep2);
    }

    @Override
    public boolean isFaulty(Node.Id node)
    {
        return mapper.nodeStatus(node) != HEALTHY;
    }

    private static class SortableEndpoints extends ArrayList<InetAddressAndPort> implements Sortable<InetAddressAndPort, SortableEndpoints>

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