# Ray cross language support doesn't support trace

**URL:** <https://discuss.ray.io/t/ray-cross-language-support-doesnt-support-trace/11693>\
**Category:** Ray Core\
**Created:** [August 6, 2023, 2:01am UTC](https://discuss.ray.io/t/ray-cross-language-support-doesnt-support-trace/11693 "2023-08-06T02:01:40Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![hliu8dsfsf](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/hliu8dsfsf/32/4881_2.png) [@hliu8dsfsf](https://discuss.ray.io/u/hliu8dsfsf)\
**Post date:** [August 6, 2023, 2:01am UTC](https://discuss.ray.io/t/ray-cross-language-support-doesnt-support-trace/11693/1 "2023-08-06T02:01:40Z")

</div>

I guess this is a Ray bug when calling Java actors from Python, with Ray.init have tracing\_startup hook argument set. Java actor not able to initialized with exception “Cross language remote functions does not support kwargs”

It is easily reproducible with similar code like below

```auto
    ray.init(job_config=ray.job_config.JobConfig(
        code_search_path=["/Users/Shared/Projects/libs"]),
        _tracing_startup_hook="ray.util.tracing.setup_local_tmp_tracing:setup_tracing"
    )
    java_class = ray.cross_language.java_actor_class(
        "com.mycompany.ml.operators.FeatureFetcherOperator").remote("constructor argument 1")

    counter = counter_class.execute.remote("method argument 1")

```

And it will produce stack trace. Which the kwargs is set to be the tracing context.

```auto
../../build/venv/lib/python3.10/site-packages/ray/actor.py:536: in remote
    return self._remote(args=args, kwargs=kwargs, **self._default_options)
../../build/venv/lib/python3.10/site-packages/ray/util/tracing/tracing_helper.py:399: in _invocation_actor_class_remote_span
    result = method(self, args, kwargs, *_args, **_kwargs)
../../build/venv/lib/python3.10/site-packages/ray/actor.py:886: in _remote
    creation_args = cross_language._format_args(worker, args, kwargs)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

worker = <ray._private.worker.Worker object at 0x11302ffa0>, args = ('/',)
kwargs = {'_ray_trace_ctx': {'traceparent': '00-54311cd6786df9a9d82c8042ff985fbe-df997918ccbcd845-01'}}

    def _format_args(worker, args, kwargs):
        """Format args for various languages.
    
        Args:
            worker: The global worker instance.
            args: The arguments for cross language.
            kwargs: The keyword arguments for cross language.
    
        Returns:
            List of args and kwargs (if supported).
        """
        if not worker.load_code_from_local:
            raise ValueError(
                "Cross language feature needs --load-code-from-local to be set."
            )
        if kwargs:
> raise TypeError("Cross language remote functions does not support kwargs.")
E TypeError: Cross language remote functions does not support kwargs.

../../build/venv/lib/python3.10/site-packages/ray/cross_language.py:100: TypeError

```