apache/pulsar · error · RuntimeException

Thread Container only supports Java Runtime

Error message

Thread Container only supports Java Runtime

What it means

The ThreadRuntime constructor enforces that thread-based execution only supports Java functions: if instanceConfig.getFunctionDetails().getRuntime() != FunctionDetails.Runtime.JAVA it immediately throws RuntimeException('Thread Container only supports Java Runtime'). Thread containers run the function in-process, which is impossible for Python/Go functions.

Source

Thrown at pulsar-functions/runtime/src/main/java/org/apache/pulsar/functions/runtime/thread/ThreadRuntime.java:95

    ThreadRuntime(InstanceConfig instanceConfig,
                  FunctionCacheManager fnCache,
                  ThreadGroup threadGroup,
                  String jarFile,
                  String transformFunctionFile,
                  PulsarClient client,
                  ClientBuilder clientBuilder,
                  PulsarAdmin pulsarAdmin,
                  String stateStorageImplClass,
                  String stateStorageServiceUrl,
                  SecretsProvider secretsProvider,
                  FunctionCollectorRegistry collectorRegistry,
                  String narExtractionDirectory,
                  Optional<ConnectorsManager> connectorsManager,
                  Optional<FunctionsManager> functionsManager) {
        this.instanceConfig = instanceConfig;
        if (instanceConfig.getFunctionDetails().getRuntime() != FunctionDetails.Runtime.JAVA) {
            throw new RuntimeException("Thread Container only supports Java Runtime");
        }

        this.threadGroup = threadGroup;
        this.fnCache = fnCache;
        this.jarFile = jarFile;
        this.transformFunctionFile = transformFunctionFile;
        this.clientBuilder = clientBuilder;
        this.pulsarClient = client;
        this.pulsarAdmin = pulsarAdmin;
        this.stateStorageImplClass = stateStorageImplClass;
        this.stateStorageServiceUrl = stateStorageServiceUrl;
        this.secretsProvider = secretsProvider;
        this.collectorRegistry = collectorRegistry;
        this.narExtractionDirectory = narExtractionDirectory;
        this.connectorsManager = connectorsManager;
        this.functionsManager = functionsManager;
    }

View on GitHub (pinned to 820761864e)

Solutions

1. Switch the function worker to the PROCESS or KUBERNETES runtime factory, which supports Python and Go functions.
2. Resubmit the function as a Java function if the thread runtime must stay.
3. Route non-Java functions to a different worker cluster configured with a compatible runtime factory.
4. Document/enforce runtime policy per cluster so users do not submit Python/Go functions to thread-runtime workers.

Example fix

# before (worker config)
functionRuntimeFactoryClassName: org.apache.pulsar.functions.runtime.thread.ThreadRuntimeFactory
# after
functionRuntimeFactoryClassName: org.apache.pulsar.functions.runtime.process.ProcessRuntimeFactory

if (instanceConfig.getFunctionDetails().getRuntime() != FunctionDetails.Runtime.JAVA) {
    throw new IllegalArgumentException("Thread runtime workers accept JAVA functions only; use PROCESS/KUBERNETES runtime for "
        + instanceConfig.getFunctionDetails().getRuntime());
}

boolean isThreadRuntimeCompatible(FunctionDetails details) {
    return details != null && details.getRuntime() == FunctionDetails.Runtime.JAVA;
}

try {
    ThreadRuntime rt = new ThreadRuntime(...);
} catch (RuntimeException e) {
    if ("Thread Container only supports Java Runtime".equals(e.getMessage())) {
        // re-route this function to a PROCESS/KUBERNETES worker
    }
    throw e;
}

When it happens

Trigger: Configuring the function worker with functionRuntimeFactoryOptions / ThreadRuntime (thread container) while submitting or scheduling a function whose runtime is PYTHON or GO (or anything non-JAVA); constructing ThreadRuntime directly with a non-JAVA InstanceConfig.

Common situations: Worker left on the default THREAD runtime after the team starts deploying Python functions; a tenant submitting a non-Java function to a thread-runtime-only worker; copying worker configs between clusters where the other cluster used PROCESS/Kubernetes runtime.

Related errors

• Unknown component type: %s
• Access to environment variable %s is not allowed.
• PulsarAdmin is not enabled in function worker
• Getting consumer is not supported
• Not support component type

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/cb0244a08bf996de. Report an issue: GitHub.