apache/pulsar · error · IllegalArgumentException

Function name cannot be null

Error message

Function name cannot be null

What it means

doCommonChecks requires a function name; together with tenant and namespace it forms the unique function identity (tenant/namespace/name). A null or empty name makes the function unaddressable, so validation throws this IllegalArgumentException immediately.

Source

Thrown at pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/FunctionConfigUtils.java:797

    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. Set a non-empty name: functionConfig.setName("my-function").
2. Add the 'name' key to the YAML/JSON config file.
3. Check code paths that build configs dynamically to ensure the name variable is assigned before validation.
4. Remember the name must be valid within the tenant/namespace and not collide with an existing function.

Example fix

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

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

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

try {
    FunctionConfigUtils.validateNonJavaFunction(functionConfig, null);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("name")) {
        throw new IllegalStateException("Function name is required: pass --name or set 'name' in the config", e);
    }
    throw e;
}

When it happens

Trigger: Creating or updating a function with a FunctionConfig whose getName() is null/empty — via validateJavaFunction/validateNonJavaFunction, the functions worker REST API, or pulsar-admin functions create without --name or with a config file lacking the 'name' key.

Common situations: Programmatic config building where name was overlooked; YAML/JSON templates missing 'name'; dynamic generation of configs in loops where the name variable was never assigned; refactors renaming the setter that left the call site behind.

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 namespace 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/a9342d2c92c14515. Report an issue: GitHub.