apache/pulsar · error · IllegalArgumentException

Function namespace cannot be null

Error message

Function namespace cannot be null

What it means

doCommonChecks requires a namespace on the function config; the namespace is the second segment of the fully-qualified function name (tenant/namespace/name). When getNamespace() is null or empty, validation throws this IllegalArgumentException before any submit reaches the functions worker.

Source

Thrown at pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/FunctionConfigUtils.java:794

        }
    }

    private static void verifyNoTopicClash(Collection<String> inputTopics, String outputTopic)
            throws IllegalArgumentException {
        if (inputTopics.contains(outputTopic)) {
            throw new IllegalArgumentException(
                    String.format(
                            "Output topic %s is also being used as an input topic (topics must be one or the other)",
                            outputTopic));
        }
    }

    public static void doCommonChecks(FunctionConfig functionConfig) {
        if (isEmpty(functionConfig.getTenant())) {
            throw new IllegalArgumentException("Function tenant cannot be null");
        }
        if (isEmpty(functionConfig.getNamespace())) {
            throw new IllegalArgumentException("Function namespace cannot be null");
        }
        if (isEmpty(functionConfig.getName())) {
            throw new IllegalArgumentException("Function name cannot be null");
        }
        // go doesn't need className. Java className is done in doJavaChecks.
        if (functionConfig.getRuntime() == FunctionConfig.Runtime.PYTHON) {
            if (isEmpty(functionConfig.getClassName())) {
                throw new IllegalArgumentException("Function classname cannot be null");
            }
        }

        Collection<String> allInputTopics = collectAllInputTopics(functionConfig);
        if (allInputTopics.isEmpty()) {
            throw new IllegalArgumentException("No input topic(s) specified for the function");
        }
        for (String topic : allInputTopics) {
            if (!TopicName.isValid(topic)) {
                throw new IllegalArgumentException(String.format("Input topic %s is invalid", topic));

View on GitHub (pinned to 820761864e)

Solutions

1. Call functionConfig.setNamespace("default") (or the intended namespace) before submitting.
2. Add the missing 'namespace' key to the YAML/JSON config file.
3. Ensure the namespace exists under the tenant (create it via pulsar-admin namespaces create if needed).
4. After deserialization, check the value is non-null and non-empty before calling create.

Example fix

// before
config.setTenant("public");
config.setName("my-fn");
// after
config.setTenant("public");
config.setNamespace("default");
config.setName("my-fn");

if (config == null || config.getNamespace() == null || config.getNamespace().trim().isEmpty()) {
    throw new IllegalArgumentException("FunctionConfig.namespace must be set before submission");
}

static boolean hasNamespace(FunctionConfig c) {
    return c != null && c.getNamespace() != null && !c.getNamespace().trim().isEmpty();
}

try {
    FunctionConfigUtils.validateNonJavaFunction(functionConfig, null);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("namespace")) {
        throw new IllegalStateException("Provide --namespace (e.g. default) when creating the function", e);
    }
    throw e;
}

When it happens

Trigger: Submitting a function (create/update through FunctionConfigUtils.validateJavaFunction or validateNonJavaFunction, REST API, or pulsar-admin) with a FunctionConfig lacking setNamespace(); YAML/JSON config files missing the 'namespace' key.

Common situations: Programmatic FunctionConfig construction where only tenant and name were set; hand-written YAML templates omitting 'namespace'; migration scripts that changed the config schema and dropped the namespace field.

Understand the failure class

Background: "X is required", "field cannot be empty", error-the-field-is-required: missing required-field validation errors, explained — this error's family across 39 libraries.

Related errors

• When Guarantees == ATMOST_ONCE, autoAck must be equal to tru
• Function tenant cannot be null
• Function name cannot be null
• there are redundant configure for listener `${listenerName}`
• must not specify `${hostPort}` to different listener.

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/d703c0a48e6ea400. Report an issue: GitHub.