apache/cassandra · error · RuntimeException

Not a Cassandra event class:

Error message

Not a Cassandra event class: 

What it means

DiagnosticEventPersistence.getEventClass restricts class loading to org.apache.cassandra.* event classes for security reasons. A RuntimeException is thrown when the supplied event class name is outside that namespace, preventing arbitrary class loading via JMX/diagnostic APIs.

Solutions

1. Use the correct Cassandra event class, e.g. org.apache.cassandra.diag.EventListener or one of the *DiagnosticEventService event types
2. Ensure the class name starts with org.apache.cassandra.
3. Consult org.apache.cassandra.diag.DiagnosticEventService for the list of valid event classes
4. If a custom event is needed, it must live under the org.apache.cassandra package (internal builds only)

Example fix

// before
bean.enableEventPersistence("com.example.MyEvent");
// after
bean.enableEventPersistence("org.apache.cassandra.db.commitlog.CommitLogChronicleEvent");

// reject non-Cassandra class names before calling the JMX operation
if (!eventClazz.startsWith("org.apache.cassandra."))
    throw new IllegalArgumentException("event class must be in org.apache.cassandra namespace");

try {
    bean.enableEventPersistence(eventClazz);
} catch (RuntimeException e) {
    if (e.getMessage().startsWith("Not a Cassandra event class")) {
        // fix the fully-qualified class name to org.apache.cassandra.*
    }
}

When it happens

Trigger: Calling enableEventPersistence/getEvents/disableEventPersistence with an eventClazz string not starting with "org.apache.cassandra."

Common situations: Typo in package name; passing a fully-qualified class of a third-party or application event; using an old class name after a package refactor.

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

• Event class must be of type DiagnosticEvent
• Access denied
• Access denied
• Access Denied
• access denied: + MODIFY_THREAD_PERMISSION

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/7920d5e447a518b9. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/diag/DiagnosticEventPersistence.java:137

        }
    }

    private void onEvent(DiagnosticEvent event)
    {
        Class<? extends DiagnosticEvent> cls = event.getClass();
        logger.trace("Persisting received {} event", cls.getName());
        DiagnosticEventStore<Long> store = getStore(cls);
        store.store(event);
        LastEventIdBroadcaster.instance().setLastEventId(event.getClass().getName(), store.getLastEventId());
    }

    @SuppressWarnings("unchecked")
    private Class<DiagnosticEvent> getEventClass(String eventClazz) throws ClassNotFoundException, InvalidClassException
    {
        // get class by eventClazz argument name
        // restrict class loading for security reasons
        if (!eventClazz.startsWith("org.apache.cassandra."))
            throw new RuntimeException("Not a Cassandra event class: " + eventClazz);

        Class<?> clazz = Class.forName(eventClazz, false, DiagnosticEventPersistence.class.getClassLoader());

        if (!(DiagnosticEvent.class.isAssignableFrom(clazz)))
            throw new InvalidClassException("Event class must be of type DiagnosticEvent");

        return (Class<DiagnosticEvent>) clazz.asSubclass(DiagnosticEvent.class);
    }

    private DiagnosticEventStore<Long> getStore(Class cls)
    {
        return stores.computeIfAbsent(cls, (storeKey) -> new DiagnosticEventMemoryStore());
    }
}

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