[xlang] Cross language Python support (#6709)

python/ray/cross_language.py

@@ -0,0 +1,84 @@
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from ray import Language
+from ray._raylet import JavaFunctionDescriptor
+
+__all__ = [
+    "java_function",
+    "java_actor_class",
+]
+
+
+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 Exception("Cross language feature needs "
+                        "--load-code-from-local to be set.")
+    if kwargs:
+        raise Exception("Cross language remote functions "
+                        "does not support kwargs.")
+    return args
+
+
+def get_function_descriptor_for_actor_method(
+        language, actor_creation_function_descriptor, method_name):
+    """Get function descriptor for cross language actor method call.
+
+    Args:
+        language: Target language.
+        actor_creation_function_descriptor:
+            The function signature for actor creation.
+        method_name: The name of actor method.
+
+    Returns:
+        Function descriptor for cross language actor method call.
+    """
+    if language == Language.JAVA:
+        return JavaFunctionDescriptor(
+            actor_creation_function_descriptor.class_name,
+            method_name,
+            # Currently not support call actor method with signature.
+            "")
+    else:
+        raise NotImplementedError("Cross language remote actor method "
+                                  "not support language {}".format(language))
+
+
+def java_function(class_name, function_name):
+    from ray.remote_function import RemoteFunction
+    return RemoteFunction(
+        Language.JAVA,
+        lambda *args, **kwargs: None,
+        JavaFunctionDescriptor(class_name, function_name, ""),
+        None,  # num_cpus,
+        None,  # num_gpus,
+        None,  # memory,
+        None,  # object_store_memory,
+        None,  # resources,
+        None,  # num_return_vals,
+        None,  # max_calls,
+        None)  # max_retries)
+
+
+def java_actor_class(class_name):
+    from ray.actor import ActorClass
+    return ActorClass._ray_from_function_descriptor(
+        Language.JAVA,
+        JavaFunctionDescriptor(class_name, "<init>", ""),
+        0,  # max_reconstructions,
+        None,  # num_cpus,
+        None,  # num_gpus,
+        None,  # memory,
+        None,  # object_store_memory,
+        None)  # resources,