apache/cassandra · error · org.apache.cassandra.transport.ProtocolException

Event " + eventType.name() + " not valid for protocol…

Error message

Event " + eventType.name() + " not valid for protocol version " + version

What it means

Some event types (e.g. SCHEMA_CHANGE vs. TOPOLOGY/STATUS changes) have minimum supported protocol versions. If a client registered for events on a protocol version older than the event's minimum, Event.deserialize throws this ProtocolException.

Solutions

1. Raise the client's protocol version to at least the event type's minimumVersion.
2. Filter out event types unsupported by the negotiated version before REGISTERing.
3. Upgrade the cluster or driver so both sides support the same protocol version set.
4. Ensure no proxy rewrites frames across protocol versions.

Example fix

// before: v3 connection receiving SCHEMA_CHANGE targeted events incorrectly
cluster.setProtocolVersion(ProtocolVersion.V3);
// after: use v4+ where the event is valid
cluster.setProtocolVersion(ProtocolVersion.V4);

ProtocolVersion v = cluster.getConfiguration().getProtocolVersion();
if (Event.Type.SCHEMA_CHANGE.minimumVersion.isGreaterThan(v))
    throw new IllegalStateException("SCHEMA_CHANGE events need protocol >= " + Event.Type.SCHEMA_CHANGE.minimumVersion);

boolean eventSupportedOn(Event.Type t, ProtocolVersion v) { return !t.minimumVersion.isGreaterThan(v); }

try { session.register(listener); } catch (ProtocolException e) {
    // bump protocol version or skip unsupported event types
}

When it happens

Trigger: A client on an old protocol version receives/submits an event frame whose Type.minimumVersion is greater than the negotiated version — typically via a REGISTER message or server push with mismatched version.

Common situations: Clients pinned to legacy protocol versions (v2/v3) that receive newer event types; proxies downgrading protocol versions; drivers built for newer servers connecting to older clusters.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• e.getMessage()
• Invalid IP address ( . . . ) while deserializing inet…
• Invalid IP address while deserializing inet address
• Unknown opcode
• Unknown option id

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/4cc97fa1f1d9c328. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/transport/Event.java:60

        Type(ProtocolVersion minimumVersion)
        {
            this.minimumVersion = minimumVersion;
        }
    }

    public final Type type;

    private Event(Type type)
    {
        this.type = type;
    }

    public static Event deserialize(ByteBuf cb, ProtocolVersion version)
    {
        Type eventType = CBUtil.readEnumValue(Type.class, cb);
        if (eventType.minimumVersion.isGreaterThan(version))
            throw new ProtocolException("Event " + eventType.name() + " not valid for protocol version " + version);
        switch (eventType)
        {
            case TOPOLOGY_CHANGE:
                return TopologyChange.deserializeEvent(cb, version);
            case STATUS_CHANGE:
                return StatusChange.deserializeEvent(cb, version);
            case SCHEMA_CHANGE:
                return SchemaChange.deserializeEvent(cb, version);
        }
        throw new AssertionError();
    }

    public void serialize(ByteBuf dest, ProtocolVersion version)
    {
        if (type.minimumVersion.isGreaterThan(version))
            throw new ProtocolException("Event " + type.name() + " not valid for protocol version " + version);
        CBUtil.writeEnumValue(type, dest);
        serializeEvent(dest, version);

View on GitHub (pinned to 88fd0f6a0e)