#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You 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.
#
"""For internal use only; no backwards-compatibility guarantees."""
from __future__ import absolute_import
import abc
import inspect
from builtins import object
from google.protobuf import message
from google.protobuf import wrappers_pb2
from apache_beam.internal import pickler
from apache_beam.utils import proto_utils
[docs]class RunnerApiFn(object):
"""Abstract base class that provides urn registration utilities.
A class that inherits from this class will get a registration-based
from_runner_api and to_runner_api method that convert to and from
beam_runner_api_pb2.SdkFunctionSpec.
Additionally, register_pickle_urn can be called from the body of a class
to register serialization via pickling.
"""
# TODO(BEAM-2685): Issue with dill + local classes + abc metaclass
# __metaclass__ = abc.ABCMeta
_known_urns = {}
[docs] @abc.abstractmethod
def to_runner_api_parameter(self, unused_context):
"""Returns the urn and payload for this Fn.
The returned urn(s) should be registered with `register_urn`.
"""
pass
[docs] @classmethod
def register_urn(cls, urn, parameter_type, fn=None):
"""Registers a urn with a constructor.
For example, if 'beam:fn:foo' had parameter type FooPayload, one could
write `RunnerApiFn.register_urn('bean:fn:foo', FooPayload, foo_from_proto)`
where foo_from_proto took as arguments a FooPayload and a PipelineContext.
This function can also be used as a decorator rather than passing the
callable in as the final parameter.
A corresponding to_runner_api_parameter method would be expected that
returns the tuple ('beam:fn:foo', FooPayload)
"""
def register(fn):
cls._known_urns[urn] = parameter_type, fn
return staticmethod(fn)
if fn:
# Used as a statement.
register(fn)
else:
# Used as a decorator.
return register
[docs] @classmethod
def register_pickle_urn(cls, pickle_urn):
"""Registers and implements the given urn via pickling.
"""
inspect.currentframe().f_back.f_locals['to_runner_api_parameter'] = (
lambda self, context: (
pickle_urn, wrappers_pb2.BytesValue(value=pickler.dumps(self))))
cls.register_urn(
pickle_urn,
wrappers_pb2.BytesValue,
lambda proto, unused_context: pickler.loads(proto.value))
[docs] def to_runner_api(self, context):
"""Returns an SdkFunctionSpec encoding this Fn.
Prefer overriding self.to_runner_api_parameter.
"""
from apache_beam.portability.api import beam_runner_api_pb2
urn, typed_param = self.to_runner_api_parameter(context)
return beam_runner_api_pb2.SdkFunctionSpec(
environment_id=context.default_environment_id(),
spec=beam_runner_api_pb2.FunctionSpec(
urn=urn,
payload=typed_param.SerializeToString()
if isinstance(typed_param, message.Message)
else typed_param))
[docs] @classmethod
def from_runner_api(cls, fn_proto, context):
"""Converts from an SdkFunctionSpec to a Fn object.
Prefer registering a urn with its parameter type and constructor.
"""
parameter_type, constructor = cls._known_urns[fn_proto.spec.urn]
return constructor(
proto_utils.parse_Bytes(fn_proto.spec.payload, parameter_type),
context)