apache/cassandra · error · InvalidRequestException

this + " is not supported as conditional update commit…

Error message

this + " is not supported as conditional update commit consistency. Use ANY if you mean \"make sure it is accepted but I don't care how many replicas commit it for non-SERIAL reads\""

What it means

validateForCasCommit checks the consistency level at which the commit phase of a lightweight transaction is performed. Serial-family levels are illegal there (the serial phase already handled them), and only levels backed by NetworkTopologyStrategy make sense for the topology-aware checks. The error message hints that ANY is the intended level for callers that do not care how many replicas commit.

Solutions

Set the LWT commit consistency to ANY (or SERIAL for the serial phase only, via serial consistency).
Use SimpleStrategy-free keyspace config: create the keyspace with NetworkTopologyStrategy if using LOCAL_SERIAL/topology-aware levels.
In drivers, explicitly pass both consistency levels for LWTs: serial consistency for the Paxos phase, QUORUM/ANY for the commit.
Review documentation for the two-consistency model of lightweight transactions.

Example fix

// before
stmt.setConsistencyLevel(ConsistencyLevel.LOCAL_SERIAL); // used as commit CL
// after
stmt.setConsistencyLevel(ConsistencyLevel.ANY);
stmt.setSerialConsistencyLevel(ConsistencyLevel.LOCAL_SERIAL);

Defensive patterns

Strategy: validation

Validate before calling

// Ensure commit CL is not serial and keyspace uses NTS
if (cl.isSerialConsistency())
    throw new IllegalArgumentException("use serial CL as serial consistency, not commit CL");

Try / catch

catch (InvalidRequestException e) {
    if (e.getMessage().contains("conditional update commit consistency")) {
        statement.setConsistencyLevel(ConsistencyLevel.ANY); // or QUORUM
        retry();
    } else throw e;
}

Prevention

For LWTs always pass commit CL (e.g. QUORUM/LOCAL_QUORUM/ANY) separately from serial CL.
Use NetworkTopologyStrategy for any keyspace touched by topology-aware CAS.
Avoid frameworks that copy one CL into both slots of an LWT.
Review the LWT documentation before configuring serial/commit levels.

When it happens

Trigger: Executing a conditional update (LWT) whose commit consistency is SERIAL/LOCAL_SERIAL/UNSAFE_DELAY_*, or a serial commit consistency with a keyspace not using NetworkTopologyStrategy for topology-requiring levels.

Common situations: Drivers letting users set one consistency for the whole LWT; misconfigured keyspace replication (SimpleStrategy) while using LOCAL_SERIAL; tutorials conflating serial and commit consistencies.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/af86bd9f2567cc50. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/ConsistencyLevel.java:253

            case LOCAL_SERIAL:
            case UNSAFE_DELAY_LOCAL_SERIAL:
                throw new InvalidRequestException("You must use conditional updates for serializable writes");
        }
    }

    // This is the same than validateForWrite really, but we include a slightly different error message for SERIAL/LOCAL_SERIAL
    public void validateForCasCommit(AbstractReplicationStrategy replicationStrategy) throws InvalidRequestException
    {
        switch (this)
        {
            case EACH_QUORUM:
                requireNetworkTopologyStrategy(replicationStrategy);
                break;
            case SERIAL:
            case UNSAFE_DELAY_SERIAL:
            case LOCAL_SERIAL:
            case UNSAFE_DELAY_LOCAL_SERIAL:
                throw new InvalidRequestException(this + " is not supported as conditional update commit consistency. Use ANY if you mean \"make sure it is accepted but I don't care how many replicas commit it for non-SERIAL reads\"");
        }
    }

    public void validateForCas() throws InvalidRequestException
    {
        if (!isSerialConsistency())
            throw new InvalidRequestException("Invalid consistency for conditional update. Must be one of SERIAL or LOCAL_SERIAL");
    }

    public boolean isSerialConsistency()
    {
        switch (this)
        {
            case SERIAL:
            case UNSAFE_DELAY_SERIAL:
            case LOCAL_SERIAL:
            case UNSAFE_DELAY_LOCAL_SERIAL:
                return true;

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