add ydb deps

1 files changed, 1003 insertions, 0 deletions

diff --git a/contrib/python/grpcio/py2/grpc/_server.py b/contrib/python/grpcio/py2/grpc/_server.py
new file mode 100644
index 0000000000..58ab14feb3
--- /dev/null
+++ b/contrib/python/grpcio/py2/grpc/_server.py
@@ -0,0 +1,1003 @@
+# Copyright 2016 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Service-side implementation of gRPC Python."""
+
+import collections
+from concurrent import futures
+import enum
+import logging
+import threading
+import time
+
+import grpc
+from grpc import _common
+from grpc import _compression
+from grpc import _interceptor
+from grpc._cython import cygrpc
+import six
+
+_LOGGER = logging.getLogger(__name__)
+
+_SHUTDOWN_TAG = 'shutdown'
+_REQUEST_CALL_TAG = 'request_call'
+
+_RECEIVE_CLOSE_ON_SERVER_TOKEN = 'receive_close_on_server'
+_SEND_INITIAL_METADATA_TOKEN = 'send_initial_metadata'
+_RECEIVE_MESSAGE_TOKEN = 'receive_message'
+_SEND_MESSAGE_TOKEN = 'send_message'
+_SEND_INITIAL_METADATA_AND_SEND_MESSAGE_TOKEN = (
+    'send_initial_metadata * send_message')
+_SEND_STATUS_FROM_SERVER_TOKEN = 'send_status_from_server'
+_SEND_INITIAL_METADATA_AND_SEND_STATUS_FROM_SERVER_TOKEN = (
+    'send_initial_metadata * send_status_from_server')
+
+_OPEN = 'open'
+_CLOSED = 'closed'
+_CANCELLED = 'cancelled'
+
+_EMPTY_FLAGS = 0
+
+_DEALLOCATED_SERVER_CHECK_PERIOD_S = 1.0
+_INF_TIMEOUT = 1e9
+
+
+def _serialized_request(request_event):
+    return request_event.batch_operations[0].message()
+
+
+def _application_code(code):
+    cygrpc_code = _common.STATUS_CODE_TO_CYGRPC_STATUS_CODE.get(code)
+    return cygrpc.StatusCode.unknown if cygrpc_code is None else cygrpc_code
+
+
+def _completion_code(state):
+    if state.code is None:
+        return cygrpc.StatusCode.ok
+    else:
+        return _application_code(state.code)
+
+
+def _abortion_code(state, code):
+    if state.code is None:
+        return code
+    else:
+        return _application_code(state.code)
+
+
+def _details(state):
+    return b'' if state.details is None else state.details
+
+
+class _HandlerCallDetails(
+        collections.namedtuple('_HandlerCallDetails', (
+            'method',
+            'invocation_metadata',
+        )), grpc.HandlerCallDetails):
+    pass
+
+
+class _RPCState(object):
+
+    def __init__(self):
+        self.condition = threading.Condition()
+        self.due = set()
+        self.request = None
+        self.client = _OPEN
+        self.initial_metadata_allowed = True
+        self.compression_algorithm = None
+        self.disable_next_compression = False
+        self.trailing_metadata = None
+        self.code = None
+        self.details = None
+        self.statused = False
+        self.rpc_errors = []
+        self.callbacks = []
+        self.aborted = False
+
+
+def _raise_rpc_error(state):
+    rpc_error = grpc.RpcError()
+    state.rpc_errors.append(rpc_error)
+    raise rpc_error
+
+
+def _possibly_finish_call(state, token):
+    state.due.remove(token)
+    if not _is_rpc_state_active(state) and not state.due:
+        callbacks = state.callbacks
+        state.callbacks = None
+        return state, callbacks
+    else:
+        return None, ()
+
+
+def _send_status_from_server(state, token):
+
+    def send_status_from_server(unused_send_status_from_server_event):
+        with state.condition:
+            return _possibly_finish_call(state, token)
+
+    return send_status_from_server
+
+
+def _get_initial_metadata(state, metadata):
+    with state.condition:
+        if state.compression_algorithm:
+            compression_metadata = (
+                _compression.compression_algorithm_to_metadata(
+                    state.compression_algorithm),)
+            if metadata is None:
+                return compression_metadata
+            else:
+                return compression_metadata + tuple(metadata)
+        else:
+            return metadata
+
+
+def _get_initial_metadata_operation(state, metadata):
+    operation = cygrpc.SendInitialMetadataOperation(
+        _get_initial_metadata(state, metadata), _EMPTY_FLAGS)
+    return operation
+
+
+def _abort(state, call, code, details):
+    if state.client is not _CANCELLED:
+        effective_code = _abortion_code(state, code)
+        effective_details = details if state.details is None else state.details
+        if state.initial_metadata_allowed:
+            operations = (
+                _get_initial_metadata_operation(state, None),
+                cygrpc.SendStatusFromServerOperation(state.trailing_metadata,
+                                                     effective_code,
+                                                     effective_details,
+                                                     _EMPTY_FLAGS),
+            )
+            token = _SEND_INITIAL_METADATA_AND_SEND_STATUS_FROM_SERVER_TOKEN
+        else:
+            operations = (cygrpc.SendStatusFromServerOperation(
+                state.trailing_metadata, effective_code, effective_details,
+                _EMPTY_FLAGS),)
+            token = _SEND_STATUS_FROM_SERVER_TOKEN
+        call.start_server_batch(operations,
+                                _send_status_from_server(state, token))
+        state.statused = True
+        state.due.add(token)
+
+
+def _receive_close_on_server(state):
+
+    def receive_close_on_server(receive_close_on_server_event):
+        with state.condition:
+            if receive_close_on_server_event.batch_operations[0].cancelled():
+                state.client = _CANCELLED
+            elif state.client is _OPEN:
+                state.client = _CLOSED
+            state.condition.notify_all()
+            return _possibly_finish_call(state, _RECEIVE_CLOSE_ON_SERVER_TOKEN)
+
+    return receive_close_on_server
+
+
+def _receive_message(state, call, request_deserializer):
+
+    def receive_message(receive_message_event):
+        serialized_request = _serialized_request(receive_message_event)
+        if serialized_request is None:
+            with state.condition:
+                if state.client is _OPEN:
+                    state.client = _CLOSED
+                state.condition.notify_all()
+                return _possibly_finish_call(state, _RECEIVE_MESSAGE_TOKEN)
+        else:
+            request = _common.deserialize(serialized_request,
+                                          request_deserializer)
+            with state.condition:
+                if request is None:
+                    _abort(state, call, cygrpc.StatusCode.internal,
+                           b'Exception deserializing request!')
+                else:
+                    state.request = request
+                state.condition.notify_all()
+                return _possibly_finish_call(state, _RECEIVE_MESSAGE_TOKEN)
+
+    return receive_message
+
+
+def _send_initial_metadata(state):
+
+    def send_initial_metadata(unused_send_initial_metadata_event):
+        with state.condition:
+            return _possibly_finish_call(state, _SEND_INITIAL_METADATA_TOKEN)
+
+    return send_initial_metadata
+
+
+def _send_message(state, token):
+
+    def send_message(unused_send_message_event):
+        with state.condition:
+            state.condition.notify_all()
+            return _possibly_finish_call(state, token)
+
+    return send_message
+
+
+class _Context(grpc.ServicerContext):
+
+    def __init__(self, rpc_event, state, request_deserializer):
+        self._rpc_event = rpc_event
+        self._state = state
+        self._request_deserializer = request_deserializer
+
+    def is_active(self):
+        with self._state.condition:
+            return _is_rpc_state_active(self._state)
+
+    def time_remaining(self):
+        return max(self._rpc_event.call_details.deadline - time.time(), 0)
+
+    def cancel(self):
+        self._rpc_event.call.cancel()
+
+    def add_callback(self, callback):
+        with self._state.condition:
+            if self._state.callbacks is None:
+                return False
+            else:
+                self._state.callbacks.append(callback)
+                return True
+
+    def disable_next_message_compression(self):
+        with self._state.condition:
+            self._state.disable_next_compression = True
+
+    def invocation_metadata(self):
+        return self._rpc_event.invocation_metadata
+
+    def peer(self):
+        return _common.decode(self._rpc_event.call.peer())
+
+    def peer_identities(self):
+        return cygrpc.peer_identities(self._rpc_event.call)
+
+    def peer_identity_key(self):
+        id_key = cygrpc.peer_identity_key(self._rpc_event.call)
+        return id_key if id_key is None else _common.decode(id_key)
+
+    def auth_context(self):
+        return {
+            _common.decode(key): value for key, value in six.iteritems(
+                cygrpc.auth_context(self._rpc_event.call))
+        }
+
+    def set_compression(self, compression):
+        with self._state.condition:
+            self._state.compression_algorithm = compression
+
+    def send_initial_metadata(self, initial_metadata):
+        with self._state.condition:
+            if self._state.client is _CANCELLED:
+                _raise_rpc_error(self._state)
+            else:
+                if self._state.initial_metadata_allowed:
+                    operation = _get_initial_metadata_operation(
+                        self._state, initial_metadata)
+                    self._rpc_event.call.start_server_batch(
+                        (operation,), _send_initial_metadata(self._state))
+                    self._state.initial_metadata_allowed = False
+                    self._state.due.add(_SEND_INITIAL_METADATA_TOKEN)
+                else:
+                    raise ValueError('Initial metadata no longer allowed!')
+
+    def set_trailing_metadata(self, trailing_metadata):
+        with self._state.condition:
+            self._state.trailing_metadata = trailing_metadata
+
+    def trailing_metadata(self):
+        return self._state.trailing_metadata
+
+    def abort(self, code, details):
+        # treat OK like other invalid arguments: fail the RPC
+        if code == grpc.StatusCode.OK:
+            _LOGGER.error(
+                'abort() called with StatusCode.OK; returning UNKNOWN')
+            code = grpc.StatusCode.UNKNOWN
+            details = ''
+        with self._state.condition:
+            self._state.code = code
+            self._state.details = _common.encode(details)
+            self._state.aborted = True
+            raise Exception()
+
+    def abort_with_status(self, status):
+        self._state.trailing_metadata = status.trailing_metadata
+        self.abort(status.code, status.details)
+
+    def set_code(self, code):
+        with self._state.condition:
+            self._state.code = code
+
+    def code(self):
+        return self._state.code
+
+    def set_details(self, details):
+        with self._state.condition:
+            self._state.details = _common.encode(details)
+
+    def details(self):
+        return self._state.details
+
+    def _finalize_state(self):
+        pass
+
+
+class _RequestIterator(object):
+
+    def __init__(self, state, call, request_deserializer):
+        self._state = state
+        self._call = call
+        self._request_deserializer = request_deserializer
+
+    def _raise_or_start_receive_message(self):
+        if self._state.client is _CANCELLED:
+            _raise_rpc_error(self._state)
+        elif not _is_rpc_state_active(self._state):
+            raise StopIteration()
+        else:
+            self._call.start_server_batch(
+                (cygrpc.ReceiveMessageOperation(_EMPTY_FLAGS),),
+                _receive_message(self._state, self._call,
+                                 self._request_deserializer))
+            self._state.due.add(_RECEIVE_MESSAGE_TOKEN)
+
+    def _look_for_request(self):
+        if self._state.client is _CANCELLED:
+            _raise_rpc_error(self._state)
+        elif (self._state.request is None and
+              _RECEIVE_MESSAGE_TOKEN not in self._state.due):
+            raise StopIteration()
+        else:
+            request = self._state.request
+            self._state.request = None
+            return request
+
+        raise AssertionError()  # should never run
+
+    def _next(self):
+        with self._state.condition:
+            self._raise_or_start_receive_message()
+            while True:
+                self._state.condition.wait()
+                request = self._look_for_request()
+                if request is not None:
+                    return request
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        return self._next()
+
+    def next(self):
+        return self._next()
+
+
+def _unary_request(rpc_event, state, request_deserializer):
+
+    def unary_request():
+        with state.condition:
+            if not _is_rpc_state_active(state):
+                return None
+            else:
+                rpc_event.call.start_server_batch(
+                    (cygrpc.ReceiveMessageOperation(_EMPTY_FLAGS),),
+                    _receive_message(state, rpc_event.call,
+                                     request_deserializer))
+                state.due.add(_RECEIVE_MESSAGE_TOKEN)
+                while True:
+                    state.condition.wait()
+                    if state.request is None:
+                        if state.client is _CLOSED:
+                            details = '"{}" requires exactly one request message.'.format(
+                                rpc_event.call_details.method)
+                            _abort(state, rpc_event.call,
+                                   cygrpc.StatusCode.unimplemented,
+                                   _common.encode(details))
+                            return None
+                        elif state.client is _CANCELLED:
+                            return None
+                    else:
+                        request = state.request
+                        state.request = None
+                        return request
+
+    return unary_request
+
+
+def _call_behavior(rpc_event,
+                   state,
+                   behavior,
+                   argument,
+                   request_deserializer,
+                   send_response_callback=None):
+    from grpc import _create_servicer_context
+    with _create_servicer_context(rpc_event, state,
+                                  request_deserializer) as context:
+        try:
+            response_or_iterator = None
+            if send_response_callback is not None:
+                response_or_iterator = behavior(argument, context,
+                                                send_response_callback)
+            else:
+                response_or_iterator = behavior(argument, context)
+            return response_or_iterator, True
+        except Exception as exception:  # pylint: disable=broad-except
+            with state.condition:
+                if state.aborted:
+                    _abort(state, rpc_event.call, cygrpc.StatusCode.unknown,
+                           b'RPC Aborted')
+                elif exception not in state.rpc_errors:
+                    details = 'Exception calling application: {}'.format(
+                        exception)
+                    _LOGGER.exception(details)
+                    _abort(state, rpc_event.call, cygrpc.StatusCode.unknown,
+                           _common.encode(details))
+            return None, False
+
+
+def _take_response_from_response_iterator(rpc_event, state, response_iterator):
+    try:
+        return next(response_iterator), True
+    except StopIteration:
+        return None, True
+    except Exception as exception:  # pylint: disable=broad-except
+        with state.condition:
+            if state.aborted:
+                _abort(state, rpc_event.call, cygrpc.StatusCode.unknown,
+                       b'RPC Aborted')
+            elif exception not in state.rpc_errors:
+                details = 'Exception iterating responses: {}'.format(exception)
+                _LOGGER.exception(details)
+                _abort(state, rpc_event.call, cygrpc.StatusCode.unknown,
+                       _common.encode(details))
+        return None, False
+
+
+def _serialize_response(rpc_event, state, response, response_serializer):
+    serialized_response = _common.serialize(response, response_serializer)
+    if serialized_response is None:
+        with state.condition:
+            _abort(state, rpc_event.call, cygrpc.StatusCode.internal,
+                   b'Failed to serialize response!')
+        return None
+    else:
+        return serialized_response
+
+
+def _get_send_message_op_flags_from_state(state):
+    if state.disable_next_compression:
+        return cygrpc.WriteFlag.no_compress
+    else:
+        return _EMPTY_FLAGS
+
+
+def _reset_per_message_state(state):
+    with state.condition:
+        state.disable_next_compression = False
+
+
+def _send_response(rpc_event, state, serialized_response):
+    with state.condition:
+        if not _is_rpc_state_active(state):
+            return False
+        else:
+            if state.initial_metadata_allowed:
+                operations = (
+                    _get_initial_metadata_operation(state, None),
+                    cygrpc.SendMessageOperation(
+                        serialized_response,
+                        _get_send_message_op_flags_from_state(state)),
+                )
+                state.initial_metadata_allowed = False
+                token = _SEND_INITIAL_METADATA_AND_SEND_MESSAGE_TOKEN
+            else:
+                operations = (cygrpc.SendMessageOperation(
+                    serialized_response,
+                    _get_send_message_op_flags_from_state(state)),)
+                token = _SEND_MESSAGE_TOKEN
+            rpc_event.call.start_server_batch(operations,
+                                              _send_message(state, token))
+            state.due.add(token)
+            _reset_per_message_state(state)
+            while True:
+                state.condition.wait()
+                if token not in state.due:
+                    return _is_rpc_state_active(state)
+
+
+def _status(rpc_event, state, serialized_response):
+    with state.condition:
+        if state.client is not _CANCELLED:
+            code = _completion_code(state)
+            details = _details(state)
+            operations = [
+                cygrpc.SendStatusFromServerOperation(state.trailing_metadata,
+                                                     code, details,
+                                                     _EMPTY_FLAGS),
+            ]
+            if state.initial_metadata_allowed:
+                operations.append(_get_initial_metadata_operation(state, None))
+            if serialized_response is not None:
+                operations.append(
+                    cygrpc.SendMessageOperation(
+                        serialized_response,
+                        _get_send_message_op_flags_from_state(state)))
+            rpc_event.call.start_server_batch(
+                operations,
+                _send_status_from_server(state, _SEND_STATUS_FROM_SERVER_TOKEN))
+            state.statused = True
+            _reset_per_message_state(state)
+            state.due.add(_SEND_STATUS_FROM_SERVER_TOKEN)
+
+
+def _unary_response_in_pool(rpc_event, state, behavior, argument_thunk,
+                            request_deserializer, response_serializer):
+    cygrpc.install_context_from_request_call_event(rpc_event)
+    try:
+        argument = argument_thunk()
+        if argument is not None:
+            response, proceed = _call_behavior(rpc_event, state, behavior,
+                                               argument, request_deserializer)
+            if proceed:
+                serialized_response = _serialize_response(
+                    rpc_event, state, response, response_serializer)
+                if serialized_response is not None:
+                    _status(rpc_event, state, serialized_response)
+    finally:
+        cygrpc.uninstall_context()
+
+
+def _stream_response_in_pool(rpc_event, state, behavior, argument_thunk,
+                             request_deserializer, response_serializer):
+    cygrpc.install_context_from_request_call_event(rpc_event)
+
+    def send_response(response):
+        if response is None:
+            _status(rpc_event, state, None)
+        else:
+            serialized_response = _serialize_response(rpc_event, state,
+                                                      response,
+                                                      response_serializer)
+            if serialized_response is not None:
+                _send_response(rpc_event, state, serialized_response)
+
+    try:
+        argument = argument_thunk()
+        if argument is not None:
+            if hasattr(behavior, 'experimental_non_blocking'
+                      ) and behavior.experimental_non_blocking:
+                _call_behavior(rpc_event,
+                               state,
+                               behavior,
+                               argument,
+                               request_deserializer,
+                               send_response_callback=send_response)
+            else:
+                response_iterator, proceed = _call_behavior(
+                    rpc_event, state, behavior, argument, request_deserializer)
+                if proceed:
+                    _send_message_callback_to_blocking_iterator_adapter(
+                        rpc_event, state, send_response, response_iterator)
+    finally:
+        cygrpc.uninstall_context()
+
+
+def _is_rpc_state_active(state):
+    return state.client is not _CANCELLED and not state.statused
+
+
+def _send_message_callback_to_blocking_iterator_adapter(rpc_event, state,
+                                                        send_response_callback,
+                                                        response_iterator):
+    while True:
+        response, proceed = _take_response_from_response_iterator(
+            rpc_event, state, response_iterator)
+        if proceed:
+            send_response_callback(response)
+            if not _is_rpc_state_active(state):
+                break
+        else:
+            break
+
+
+def _select_thread_pool_for_behavior(behavior, default_thread_pool):
+    if hasattr(behavior, 'experimental_thread_pool') and isinstance(
+            behavior.experimental_thread_pool, futures.ThreadPoolExecutor):
+        return behavior.experimental_thread_pool
+    else:
+        return default_thread_pool
+
+
+def _handle_unary_unary(rpc_event, state, method_handler, default_thread_pool):
+    unary_request = _unary_request(rpc_event, state,
+                                   method_handler.request_deserializer)
+    thread_pool = _select_thread_pool_for_behavior(method_handler.unary_unary,
+                                                   default_thread_pool)
+    return thread_pool.submit(_unary_response_in_pool, rpc_event, state,
+                              method_handler.unary_unary, unary_request,
+                              method_handler.request_deserializer,
+                              method_handler.response_serializer)
+
+
+def _handle_unary_stream(rpc_event, state, method_handler, default_thread_pool):
+    unary_request = _unary_request(rpc_event, state,
+                                   method_handler.request_deserializer)
+    thread_pool = _select_thread_pool_for_behavior(method_handler.unary_stream,
+                                                   default_thread_pool)
+    return thread_pool.submit(_stream_response_in_pool, rpc_event, state,
+                              method_handler.unary_stream, unary_request,
+                              method_handler.request_deserializer,
+                              method_handler.response_serializer)
+
+
+def _handle_stream_unary(rpc_event, state, method_handler, default_thread_pool):
+    request_iterator = _RequestIterator(state, rpc_event.call,
+                                        method_handler.request_deserializer)
+    thread_pool = _select_thread_pool_for_behavior(method_handler.stream_unary,
+                                                   default_thread_pool)
+    return thread_pool.submit(_unary_response_in_pool, rpc_event, state,
+                              method_handler.stream_unary,
+                              lambda: request_iterator,
+                              method_handler.request_deserializer,
+                              method_handler.response_serializer)
+
+
+def _handle_stream_stream(rpc_event, state, method_handler,
+                          default_thread_pool):
+    request_iterator = _RequestIterator(state, rpc_event.call,
+                                        method_handler.request_deserializer)
+    thread_pool = _select_thread_pool_for_behavior(method_handler.stream_stream,
+                                                   default_thread_pool)
+    return thread_pool.submit(_stream_response_in_pool, rpc_event, state,
+                              method_handler.stream_stream,
+                              lambda: request_iterator,
+                              method_handler.request_deserializer,
+                              method_handler.response_serializer)
+
+
+def _find_method_handler(rpc_event, generic_handlers, interceptor_pipeline):
+
+    def query_handlers(handler_call_details):
+        for generic_handler in generic_handlers:
+            method_handler = generic_handler.service(handler_call_details)
+            if method_handler is not None:
+                return method_handler
+        return None
+
+    handler_call_details = _HandlerCallDetails(
+        _common.decode(rpc_event.call_details.method),
+        rpc_event.invocation_metadata)
+
+    if interceptor_pipeline is not None:
+        return interceptor_pipeline.execute(query_handlers,
+                                            handler_call_details)
+    else:
+        return query_handlers(handler_call_details)
+
+
+def _reject_rpc(rpc_event, status, details):
+    rpc_state = _RPCState()
+    operations = (
+        _get_initial_metadata_operation(rpc_state, None),
+        cygrpc.ReceiveCloseOnServerOperation(_EMPTY_FLAGS),
+        cygrpc.SendStatusFromServerOperation(None, status, details,
+                                             _EMPTY_FLAGS),
+    )
+    rpc_event.call.start_server_batch(operations, lambda ignored_event: (
+        rpc_state,
+        (),
+    ))
+    return rpc_state
+
+
+def _handle_with_method_handler(rpc_event, method_handler, thread_pool):
+    state = _RPCState()
+    with state.condition:
+        rpc_event.call.start_server_batch(
+            (cygrpc.ReceiveCloseOnServerOperation(_EMPTY_FLAGS),),
+            _receive_close_on_server(state))
+        state.due.add(_RECEIVE_CLOSE_ON_SERVER_TOKEN)
+        if method_handler.request_streaming:
+            if method_handler.response_streaming:
+                return state, _handle_stream_stream(rpc_event, state,
+                                                    method_handler, thread_pool)
+            else:
+                return state, _handle_stream_unary(rpc_event, state,
+                                                   method_handler, thread_pool)
+        else:
+            if method_handler.response_streaming:
+                return state, _handle_unary_stream(rpc_event, state,
+                                                   method_handler, thread_pool)
+            else:
+                return state, _handle_unary_unary(rpc_event, state,
+                                                  method_handler, thread_pool)
+
+
+def _handle_call(rpc_event, generic_handlers, interceptor_pipeline, thread_pool,
+                 concurrency_exceeded):
+    if not rpc_event.success:
+        return None, None
+    if rpc_event.call_details.method is not None:
+        try:
+            method_handler = _find_method_handler(rpc_event, generic_handlers,
+                                                  interceptor_pipeline)
+        except Exception as exception:  # pylint: disable=broad-except
+            details = 'Exception servicing handler: {}'.format(exception)
+            _LOGGER.exception(details)
+            return _reject_rpc(rpc_event, cygrpc.StatusCode.unknown,
+                               b'Error in service handler!'), None
+        if method_handler is None:
+            return _reject_rpc(rpc_event, cygrpc.StatusCode.unimplemented,
+                               b'Method not found!'), None
+        elif concurrency_exceeded:
+            return _reject_rpc(rpc_event, cygrpc.StatusCode.resource_exhausted,
+                               b'Concurrent RPC limit exceeded!'), None
+        else:
+            return _handle_with_method_handler(rpc_event, method_handler,
+                                               thread_pool)
+    else:
+        return None, None
+
+
+@enum.unique
+class _ServerStage(enum.Enum):
+    STOPPED = 'stopped'
+    STARTED = 'started'
+    GRACE = 'grace'
+
+
+class _ServerState(object):
+
+    # pylint: disable=too-many-arguments
+    def __init__(self, completion_queue, server, generic_handlers,
+                 interceptor_pipeline, thread_pool, maximum_concurrent_rpcs):
+        self.lock = threading.RLock()
+        self.completion_queue = completion_queue
+        self.server = server
+        self.generic_handlers = list(generic_handlers)
+        self.interceptor_pipeline = interceptor_pipeline
+        self.thread_pool = thread_pool
+        self.stage = _ServerStage.STOPPED
+        self.termination_event = threading.Event()
+        self.shutdown_events = [self.termination_event]
+        self.maximum_concurrent_rpcs = maximum_concurrent_rpcs
+        self.active_rpc_count = 0
+
+        # TODO(https://github.com/grpc/grpc/issues/6597): eliminate these fields.
+        self.rpc_states = set()
+        self.due = set()
+
+        # A "volatile" flag to interrupt the daemon serving thread
+        self.server_deallocated = False
+
+
+def _add_generic_handlers(state, generic_handlers):
+    with state.lock:
+        state.generic_handlers.extend(generic_handlers)
+
+
+def _add_insecure_port(state, address):
+    with state.lock:
+        return state.server.add_http2_port(address)
+
+
+def _add_secure_port(state, address, server_credentials):
+    with state.lock:
+        return state.server.add_http2_port(address,
+                                           server_credentials._credentials)
+
+
+def _request_call(state):
+    state.server.request_call(state.completion_queue, state.completion_queue,
+                              _REQUEST_CALL_TAG)
+    state.due.add(_REQUEST_CALL_TAG)
+
+
+# TODO(https://github.com/grpc/grpc/issues/6597): delete this function.
+def _stop_serving(state):
+    if not state.rpc_states and not state.due:
+        state.server.destroy()
+        for shutdown_event in state.shutdown_events:
+            shutdown_event.set()
+        state.stage = _ServerStage.STOPPED
+        return True
+    else:
+        return False
+
+
+def _on_call_completed(state):
+    with state.lock:
+        state.active_rpc_count -= 1
+
+
+def _process_event_and_continue(state, event):
+    should_continue = True
+    if event.tag is _SHUTDOWN_TAG:
+        with state.lock:
+            state.due.remove(_SHUTDOWN_TAG)
+            if _stop_serving(state):
+                should_continue = False
+    elif event.tag is _REQUEST_CALL_TAG:
+        with state.lock:
+            state.due.remove(_REQUEST_CALL_TAG)
+            concurrency_exceeded = (
+                state.maximum_concurrent_rpcs is not None and
+                state.active_rpc_count >= state.maximum_concurrent_rpcs)
+            rpc_state, rpc_future = _handle_call(event, state.generic_handlers,
+                                                 state.interceptor_pipeline,
+                                                 state.thread_pool,
+                                                 concurrency_exceeded)
+            if rpc_state is not None:
+                state.rpc_states.add(rpc_state)
+            if rpc_future is not None:
+                state.active_rpc_count += 1
+                rpc_future.add_done_callback(
+                    lambda unused_future: _on_call_completed(state))
+            if state.stage is _ServerStage.STARTED:
+                _request_call(state)
+            elif _stop_serving(state):
+                should_continue = False
+    else:
+        rpc_state, callbacks = event.tag(event)
+        for callback in callbacks:
+            try:
+                callback()
+            except Exception:  # pylint: disable=broad-except
+                _LOGGER.exception('Exception calling callback!')
+        if rpc_state is not None:
+            with state.lock:
+                state.rpc_states.remove(rpc_state)
+                if _stop_serving(state):
+                    should_continue = False
+    return should_continue
+
+
+def _serve(state):
+    while True:
+        timeout = time.time() + _DEALLOCATED_SERVER_CHECK_PERIOD_S
+        event = state.completion_queue.poll(timeout)
+        if state.server_deallocated:
+            _begin_shutdown_once(state)
+        if event.completion_type != cygrpc.CompletionType.queue_timeout:
+            if not _process_event_and_continue(state, event):
+                return
+        # We want to force the deletion of the previous event
+        # ~before~ we poll again; if the event has a reference
+        # to a shutdown Call object, this can induce spinlock.
+        event = None
+
+
+def _begin_shutdown_once(state):
+    with state.lock:
+        if state.stage is _ServerStage.STARTED:
+            state.server.shutdown(state.completion_queue, _SHUTDOWN_TAG)
+            state.stage = _ServerStage.GRACE
+            state.due.add(_SHUTDOWN_TAG)
+
+
+def _stop(state, grace):
+    with state.lock:
+        if state.stage is _ServerStage.STOPPED:
+            shutdown_event = threading.Event()
+            shutdown_event.set()
+            return shutdown_event
+        else:
+            _begin_shutdown_once(state)
+            shutdown_event = threading.Event()
+            state.shutdown_events.append(shutdown_event)
+            if grace is None:
+                state.server.cancel_all_calls()
+            else:
+
+                def cancel_all_calls_after_grace():
+                    shutdown_event.wait(timeout=grace)
+                    with state.lock:
+                        state.server.cancel_all_calls()
+
+                thread = threading.Thread(target=cancel_all_calls_after_grace)
+                thread.start()
+                return shutdown_event
+    shutdown_event.wait()
+    return shutdown_event
+
+
+def _start(state):
+    with state.lock:
+        if state.stage is not _ServerStage.STOPPED:
+            raise ValueError('Cannot start already-started server!')
+        state.server.start()
+        state.stage = _ServerStage.STARTED
+        _request_call(state)
+
+        thread = threading.Thread(target=_serve, args=(state,))
+        thread.daemon = True
+        thread.start()
+
+
+def _validate_generic_rpc_handlers(generic_rpc_handlers):
+    for generic_rpc_handler in generic_rpc_handlers:
+        service_attribute = getattr(generic_rpc_handler, 'service', None)
+        if service_attribute is None:
+            raise AttributeError(
+                '"{}" must conform to grpc.GenericRpcHandler type but does '
+                'not have "service" method!'.format(generic_rpc_handler))
+
+
+def _augment_options(base_options, compression):
+    compression_option = _compression.create_channel_option(compression)
+    return tuple(base_options) + compression_option
+
+
+class _Server(grpc.Server):
+
+    # pylint: disable=too-many-arguments
+    def __init__(self, thread_pool, generic_handlers, interceptors, options,
+                 maximum_concurrent_rpcs, compression, xds):
+        completion_queue = cygrpc.CompletionQueue()
+        server = cygrpc.Server(_augment_options(options, compression), xds)
+        server.register_completion_queue(completion_queue)
+        self._state = _ServerState(completion_queue, server, generic_handlers,
+                                   _interceptor.service_pipeline(interceptors),
+                                   thread_pool, maximum_concurrent_rpcs)
+
+    def add_generic_rpc_handlers(self, generic_rpc_handlers):
+        _validate_generic_rpc_handlers(generic_rpc_handlers)
+        _add_generic_handlers(self._state, generic_rpc_handlers)
+
+    def add_insecure_port(self, address):
+        return _common.validate_port_binding_result(
+            address, _add_insecure_port(self._state, _common.encode(address)))
+
+    def add_secure_port(self, address, server_credentials):
+        return _common.validate_port_binding_result(
+            address,
+            _add_secure_port(self._state, _common.encode(address),
+                             server_credentials))
+
+    def start(self):
+        _start(self._state)
+
+    def wait_for_termination(self, timeout=None):
+        # NOTE(https://bugs.python.org/issue35935)
+        # Remove this workaround once threading.Event.wait() is working with
+        # CTRL+C across platforms.
+        return _common.wait(self._state.termination_event.wait,
+                            self._state.termination_event.is_set,
+                            timeout=timeout)
+
+    def stop(self, grace):
+        return _stop(self._state, grace)
+
+    def __del__(self):
+        if hasattr(self, '_state'):
+            # We can not grab a lock in __del__(), so set a flag to signal the
+            # serving daemon thread (if it exists) to initiate shutdown.
+            self._state.server_deallocated = True
+
+
+def create_server(thread_pool, generic_rpc_handlers, interceptors, options,
+                  maximum_concurrent_rpcs, compression, xds):
+    _validate_generic_rpc_handlers(generic_rpc_handlers)
+    return _Server(thread_pool, generic_rpc_handlers, interceptors, options,
+                   maximum_concurrent_rpcs, compression, xds)