sdks/python/apache_beam/runners/pipeline_context.py

#
# 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.
#

"""Utility class for serializing pipelines via the runner API.

For internal use only; no backwards-compatibility guarantees.
"""

from __future__ import absolute_import

from builtins import object

from apache_beam import coders
from apache_beam import pipeline
from apache_beam import pvalue
from apache_beam.internal import pickler
from apache_beam.portability.api import beam_fn_api_pb2
from apache_beam.portability.api import beam_runner_api_pb2
from apache_beam.transforms import core


class Environment(object):
  """A wrapper around the environment proto.

  Provides consistency with how the other componentes are accessed.
  """
  def __init__(self, proto):
    self._proto = proto

  def to_runner_api(self, context):
    return self._proto

  @staticmethod
  def from_runner_api(proto, context):
    return Environment(proto)


class _PipelineContextMap(object):
  """This is a bi-directional map between objects and ids.

  Under the hood it encodes and decodes these objects into runner API
  representations.
  """
  def __init__(self, context, obj_type, namespace, proto_map=None):
    self._pipeline_context = context
    self._obj_type = obj_type
    self._namespace = namespace
    self._obj_to_id = {}
    self._id_to_obj = {}
    self._id_to_proto = dict(proto_map) if proto_map else {}
    self._counter = 0

  def _unique_ref(self, obj=None, label=None):
    self._counter += 1
    return "%s_%s_%s_%d" % (
        self._namespace,
        self._obj_type.__name__,
        label or type(obj).__name__,
        self._counter)

  def populate_map(self, proto_map):
    for id, proto in self._id_to_proto.items():
      proto_map[id].CopyFrom(proto)

  def get_id(self, obj, label=None):
    if obj not in self._obj_to_id:
      id = self._unique_ref(obj, label)
      self._id_to_obj[id] = obj
      self._obj_to_id[obj] = id
      self._id_to_proto[id] = obj.to_runner_api(self._pipeline_context)
    return self._obj_to_id[obj]

  def get_proto(self, obj, label=None):
    return self._id_to_proto[self.get_id(obj, label)]

  def get_by_id(self, id):
    if id not in self._id_to_obj:
      self._id_to_obj[id] = self._obj_type.from_runner_api(
          self._id_to_proto[id], self._pipeline_context)
    return self._id_to_obj[id]

  def get_by_proto(self, maybe_new_proto, label=None, deduplicate=False):
    if deduplicate:
      for id, proto in self._id_to_proto.items():
        if proto == maybe_new_proto:
          return id
    return self.put_proto(self._unique_ref(label), maybe_new_proto)

  def put_proto(self, id, proto):
    if id in self._id_to_proto:
      raise ValueError("Id '%s' is already taken." % id)
    self._id_to_proto[id] = proto
    return id

  def __getitem__(self, id):
    return self.get_by_id(id)

  def __contains__(self, id):
    return id in self._id_to_proto


class PipelineContext(object):
  """For internal use only; no backwards-compatibility guarantees.

  Used for accessing and constructing the referenced objects of a Pipeline.
  """

  _COMPONENT_TYPES = {
      'transforms': pipeline.AppliedPTransform,
      'pcollections': pvalue.PCollection,
      'coders': coders.Coder,
      'windowing_strategies': core.Windowing,
      'environments': Environment,
  }

  def __init__(
      self, proto=None, default_environment=None, use_fake_coders=False,
      iterable_state_read=None, iterable_state_write=None,
      namespace='ref', allow_proto_holders=False):
    if isinstance(proto, beam_fn_api_pb2.ProcessBundleDescriptor):
      proto = beam_runner_api_pb2.Components(
          coders=dict(proto.coders.items()),
          windowing_strategies=dict(proto.windowing_strategies.items()),
          environments=dict(proto.environments.items()))
    for name, cls in self._COMPONENT_TYPES.items():
      setattr(
          self, name, _PipelineContextMap(
              self, cls, namespace, getattr(proto, name, None)))
    if default_environment:
      self._default_environment_id = self.environments.get_id(
          Environment(default_environment), label='default_environment')
    else:
      self._default_environment_id = None
    self.use_fake_coders = use_fake_coders
    self.iterable_state_read = iterable_state_read
    self.iterable_state_write = iterable_state_write
    self.allow_proto_holders = allow_proto_holders

  # If fake coders are requested, return a pickled version of the element type
  # rather than an actual coder. The element type is required for some runners,
  # as well as performing a round-trip through protos.
  # TODO(BEAM-2717): Remove once this is no longer needed.
  def coder_id_from_element_type(self, element_type):
    if self.use_fake_coders:
      return pickler.dumps(element_type)
    else:
      return self.coders.get_id(coders.registry.get_coder(element_type))

  def element_type_from_coder_id(self, coder_id):
    if self.use_fake_coders or coder_id not in self.coders:
      return pickler.loads(coder_id)
    else:
      return self.coders[coder_id].to_type_hint()

  @staticmethod
  def from_runner_api(proto):
    return PipelineContext(proto)

  def to_runner_api(self):
    context_proto = beam_runner_api_pb2.Components()
    for name in self._COMPONENT_TYPES:
      getattr(self, name).populate_map(getattr(context_proto, name))
    return context_proto

  def default_environment_id(self):
    return self._default_environment_id