apache/pulsar · error · IllegalArgumentException

Source class %s implements %s but batch source source config

Error message

Source class %s implements %s but batch source source config is not specified

What it means

During source validation, Pulsar detected that the source class implements BatchSource but the SourceConfig has no batchSourceConfig set. A BatchSource requires its discovery triggerer/record generator settings to operate, so the framework refuses to deploy a batch source without that configuration block.

Source

Thrown at pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/SourceConfigUtils.java:325

        try {
            sourceClass = sourceFunction.resolveType(sourceClassName);
        } catch (TypePool.Resolution.NoSuchTypeException e) {
            throw new IllegalArgumentException(
              String.format("Source class %s not found in class loader", sourceClassName), e);
        }

        if (!(sourceClass.asErasure().isAssignableTo(Source.class) || sourceClass.asErasure()
                .isAssignableTo(BatchSource.class))) {
            throw new IllegalArgumentException(
                    String.format("Source class %s does not implement the correct interface",
                            sourceClass.getName()));
        }

        if (sourceClass.asErasure().isAssignableTo(BatchSource.class)) {
            if (sourceConfig.getBatchSourceConfig() != null) {
                validateBatchSourceConfig(sourceConfig.getBatchSourceConfig());
            } else {
                throw new IllegalArgumentException(
                  String.format("Source class %s implements %s but batch source source config is not specified",
                    sourceClass.getName(), BatchSource.class.getName()));
            }
        }

        // extract type from source class
        TypeDefinition typeArg;

        try {
            typeArg = getSourceType(sourceClass);
        } catch (Exception e) {
            throw new IllegalArgumentException(
                    String.format("Failed to resolve type for Source class %s", sourceClassName), e);
        }

        // Only one of serdeClassName or schemaType should be set
        if (!StringUtils.isEmpty(sourceConfig.getSerdeClassName()) && !StringUtils
                .isEmpty(sourceConfig.getSchemaType())) {

View on GitHub (pinned to 820761864e)

Solutions

1. Add a batchSourceConfig object (with discoveryTriggererClassName, discoveryTriggererConfig, batchSize) to the SourceConfig before submitting
2. Verify the className really needs to be a BatchSource; if a regular source suffices, use a class implementing Source instead of BatchSource
3. Check config file/JSON key spelling and nesting so batchSourceConfig actually deserializes into the SourceConfig
4. Re-submit the source with the corrected config

Example fix

// before
{"className":"com.example.MyBatchSource","topicName":"out"}
// after
{"className":"com.example.MyBatchSource","topicName":"out","batchSourceConfig":{"discoveryTriggererClassName":"com.example.MyTriggerer","discoveryTriggererConfig":{},"batchSize":10}}

if (config.getClassName() != null && isBatchSourceClass(config.getClassName(), loader)
    && config.getBatchSourceConfig() == null) {
    throw new IllegalArgumentException("batchSourceConfig required for BatchSource class " + config.getClassName());
}

boolean isBatchSourceConfigured(SourceConfig c) { return c.getBatchSourceConfig() != null; }

try { SourceConfigUtils.validateAndExtractDetails(...); } catch (IllegalArgumentException e) { if (e.getMessage().contains("batch source source config")) { /* add batchSourceConfig and retry */ } else { throw e; } }

When it happens

Trigger: Calling SourceConfigUtils.validateAndExtractDetails with a SourceConfig whose className points to a class assignable to org.apache.pulsar.functions.source.BatchSource while sourceConfig.getBatchSourceConfig() returns null.

Common situations: Deploying a batch source connector via CLI/REST and forgetting the --batch-source-config JSON; copying a regular source config template for a batch source; a config file where the batchSourceConfig key is misspelled or nested incorrectly so it deserializes to null.

Understand the failure class

Background: "X is required", "must be set", "cannot be empty": the missing-required-config error family, from Vertex AI project/location to WeChat keys — this error's family across 18 libraries.

Related errors

• BatchSourceConfig does not specify Discovery Trigger ClassNa
• Batch Configs cannot be found
• BatchSource does not implement the correct interface
• BatchSourceTriggerer does not implement the correct interfac
• error writing discovered task to intermediate topic

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/5fadac43e0e26c30. Report an issue: GitHub.