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< from concurrent.futures import ThreadPoolExecutor
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> from typing import TYPE_CHECKING
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< from optuna._experimental import experimental_func
---
> from optuna._imports import _LazyImport
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< from optuna.storages._grpc.grpc_imports import _imports
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< if _imports.is_successful():
<     from optuna.storages._grpc.grpc_imports import api_pb2
<     from optuna.storages._grpc.grpc_imports import api_pb2_grpc
<     from optuna.storages._grpc.grpc_imports import grpc
<     from optuna.storages._grpc.grpc_imports import StorageServiceServicer
< else:
---
> if TYPE_CHECKING:
>     import grpc
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<     class StorageServiceServicer:  # type: ignore
<         pass
---
>     from optuna.storages._grpc.auto_generated import api_pb2
>     from optuna.storages._grpc.auto_generated import api_pb2_grpc
> else:
>     api_pb2 = _LazyImport("optuna.storages._grpc.auto_generated.api_pb2")
>     api_pb2_grpc = _LazyImport("optuna.storages._grpc.auto_generated.api_pb2_grpc")
>     grpc = _LazyImport("grpc")
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< class OptunaStorageProxyService(StorageServiceServicer):
---
> class OptunaStorageProxyService(api_pb2_grpc.StorageServiceServicer):
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<         _imports.check()
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< 
< 
< def make_server(
<     storage: BaseStorage, host: str, port: int, thread_pool: ThreadPoolExecutor | None = None
< ) -> grpc.Server:
<     server = grpc.server(thread_pool or ThreadPoolExecutor(max_workers=10))
<     api_pb2_grpc.add_StorageServiceServicer_to_server(
<         OptunaStorageProxyService(storage), server
<     )  # type: ignore
<     server.add_insecure_port(f"{host}:{port}")
<     return server
< 
< 
< @experimental_func("4.2.0")
< def run_grpc_proxy_server(
<     storage: BaseStorage,
<     *,
<     host: str = "localhost",
<     port: int = 13000,
<     thread_pool: ThreadPoolExecutor | None = None,
< ) -> None:
<     """Run a gRPC server for the given storage URL, host, and port.
< 
<     Example:
< 
<         Run this server with the following way:
< 
<         .. code::
< 
<             from optuna.storages import run_grpc_proxy_server
<             from optuna.storages import get_storage
< 
<             storage = get_storage("mysql+pymysql://<user>:<pass>@<host>/<dbname>[?<options>]")
<             run_grpc_proxy_server(storage, host="localhost", port=13000)
< 
<         Please refer to the client class :class:`~optuna.storages.GrpcStorageProxy` for
<         the client usage. Please use :func:`~optuna.storages.get_storage` instead of
<         :class:`~optuna.storages.RDBStorage` since ``RDBStorage`` by itself does not use cache in
<         process and it may cause significant slowdown.
< 
<     Args:
<         storage: A storage object to proxy.
<         host: Hostname to listen on.
<         port: Port to listen on.
<         thread_pool:
<             Thread pool to use for the server. If :obj:`None`, a default thread pool
<             with 10 workers will be used.
<     """
<     server = make_server(storage, host, port, thread_pool)
<     server.start()
<     _logger.info(f"Server started at {host}:{port}")
<     _logger.info("Listening...")
<     server.wait_for_termination()