apache/pulsar · error · RuntimeException

Unknown runtime ${runtime}

Error message

Unknown runtime ${runtime}

What it means

FunctionActioner.getDownloadFileName maps a FunctionDetails runtime to the downloaded file extension (jar/py/go). Any runtime other than JAVA, PYTHON, or GO hits the default branch and a RuntimeException 'Unknown runtime <runtime>' is thrown.

Source

Thrown at pulsar-functions/worker/src/main/java/org/apache/pulsar/functions/worker/FunctionActioner.java:635

        }
        String[] hierarchy = functionDetails.getClassName().split("\\.");
        String fileName;
        if (hierarchy.length <= 0) {
            fileName = functionDetails.getClassName();
        } else if (hierarchy.length == 1) {
            fileName =  hierarchy[0];
        } else {
            fileName = hierarchy[hierarchy.length - 2];
        }
        switch (functionDetails.getRuntime()) {
            case JAVA:
                return fileName + ".jar";
            case PYTHON:
                return fileName + ".py";
            case GO:
                return fileName + ".go";
            default:
                throw new RuntimeException("Unknown runtime " + functionDetails.getRuntime());
        }
    }

    private void setupBatchSource(FunctionDetails functionDetails) {
        if (isBatchSource(functionDetails)) {

            String intermediateTopicName = SourceConfigUtils.computeBatchSourceIntermediateTopicName(
              functionDetails.getTenant(), functionDetails.getNamespace(), functionDetails.getName()).toString();

            String intermediateTopicSubscription = SourceConfigUtils.computeBatchSourceInstanceSubscriptionName(
              functionDetails.getTenant(), functionDetails.getNamespace(), functionDetails.getName());
            String fqfn = FunctionCommon.getFullyQualifiedName(
              functionDetails.getTenant(), functionDetails.getNamespace(), functionDetails.getName());
            try {
                Actions.newBuilder()
                  .addAction(
                    Actions.Action.builder()
                      .actionName(String.format("Creating intermediate topic"

View on GitHub (pinned to 820761864e)

Solutions

1. Use JAVA, PYTHON, or GO as the function runtime
2. Upgrade the Pulsar functions worker to a version that supports the runtime being submitted
3. Inspect the submitted FunctionDetails protobuf for a corrupted runtime value

Example fix

// before
FunctionDetails.newBuilder().setRuntime(FunctionDetails.Runtime.UNKNOWN)
// after
FunctionDetails.newBuilder().setRuntime(FunctionDetails.Runtime.JAVA)

int rt = functionDetails.getRuntime();
if (rt != FunctionDetails.Runtime.JAVA_VALUE
    && rt != FunctionDetails.Runtime.PYTHON_VALUE
    && rt != FunctionDetails.Runtime.GO_VALUE) {
    throw new IllegalArgumentException("unsupported runtime: " + rt);
}

boolean isSupportedRuntime(FunctionDetails fd) {
    switch (fd.getRuntime()) {
        case JAVA: case PYTHON: case GO: return true;
        default: return false;
    }
}

try {
    functionActioner.startFunction(...);
} catch (RuntimeException e) {
    if (e.getMessage().startsWith("Unknown runtime")) {
        // resubmit with JAVA/PYTHON/GO or upgrade the worker
    } else { throw e; }
}

When it happens

Trigger: Resolving the package file name for a function whose FunctionDetails.runtime is an unrecognized/unsupported runtime value (e.g. new runtime enum value used by a newer client against an older worker).

Common situations: Submitting functions built with a newer Pulsar client that supports runtimes the deployed worker doesn't know; corrupted/mis-serialized runtime field; custom runtime experiments.

Related errors

• Unsupported Runtime %s
• Log folder creation error
• Unsupported Runtime
• Thread Container only supports Java Runtime
• Function language runtime is either not set or cannot be det

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/a65027ef9bcf69a2. Report an issue: GitHub.