sdks/python/apache_beam/transforms/userstate.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.
#

"""User-facing interfaces for the Beam State and Timer APIs."""

# pytype: skip-file
# mypy: disallow-untyped-defs

import collections
import types
from collections.abc import Callable
from collections.abc import Iterable
from typing import TYPE_CHECKING
from typing import Any
from typing import NamedTuple
from typing import Optional
from typing import TypeVar

from apache_beam.coders import Coder
from apache_beam.coders import coders
from apache_beam.portability import common_urns
from apache_beam.portability.api import beam_runner_api_pb2
from apache_beam.transforms.timeutil import TimeDomain
from apache_beam.utils import windowed_value
from apache_beam.utils.timestamp import Timestamp

if TYPE_CHECKING:
  from apache_beam.runners.pipeline_context import PipelineContext
  from apache_beam.transforms.core import DoFn

CallableT = TypeVar('CallableT', bound=Callable)


class StateSpec(object):
  """Specification for a user DoFn state cell."""
  def __init__(self, name: str, coder: Coder) -> None:
    if not isinstance(name, str):
      raise TypeError("name is not a string")
    if not isinstance(coder, Coder):
      raise TypeError("coder is not of type Coder")
    self.name = name
    self.coder = coder

  def __repr__(self) -> str:
    return '%s(%s)' % (self.__class__.__name__, self.name)

  def to_runner_api(
      self, context: 'PipelineContext') -> beam_runner_api_pb2.StateSpec:
    raise NotImplementedError


class ReadModifyWriteStateSpec(StateSpec):
  """Specification for a user DoFn value state cell.
     Read more about ReadModifyWriteState (ValueState) here:
     https://beam.apache.org/documentation/programming-guide/#valuestate
  """
  def to_runner_api(
      self, context: 'PipelineContext') -> beam_runner_api_pb2.StateSpec:
    return beam_runner_api_pb2.StateSpec(
        read_modify_write_spec=beam_runner_api_pb2.ReadModifyWriteStateSpec(
            coder_id=context.coders.get_id(self.coder)),
        protocol=beam_runner_api_pb2.FunctionSpec(
            urn=common_urns.user_state.BAG.urn))


class BagStateSpec(StateSpec):
  """Specification for a user DoFn bag state cell.
  Read more about BagState here:
  https://beam.apache.org/documentation/programming-guide/#bagstate
  """
  def to_runner_api(
      self, context: 'PipelineContext') -> beam_runner_api_pb2.StateSpec:
    return beam_runner_api_pb2.StateSpec(
        bag_spec=beam_runner_api_pb2.BagStateSpec(
            element_coder_id=context.coders.get_id(self.coder)),
        protocol=beam_runner_api_pb2.FunctionSpec(
            urn=common_urns.user_state.BAG.urn))


class SetStateSpec(StateSpec):
  """Specification for a user DoFn Set State cell.
  Read more about SetState here:
  https://beam.apache.org/documentation/programming-guide/#setstate
  """
  def to_runner_api(
      self, context: 'PipelineContext') -> beam_runner_api_pb2.StateSpec:
    return beam_runner_api_pb2.StateSpec(
        set_spec=beam_runner_api_pb2.SetStateSpec(
            element_coder_id=context.coders.get_id(self.coder)),
        protocol=beam_runner_api_pb2.FunctionSpec(
            urn=common_urns.user_state.BAG.urn))


class CombiningValueStateSpec(StateSpec):
  """Specification for a user DoFn combining value state cell.
  Read more about CombiningValueState here:
  https://beam.apache.org/documentation/programming-guide/#combiningstate
  """
  def __init__(
      self,
      name: str,
      coder: Optional[Coder] = None,
      combine_fn: Any = None) -> None:
    """Initialize the specification for CombiningValue state.

    CombiningValueStateSpec(name, combine_fn) -> Coder-inferred combining value
      state spec.
    CombiningValueStateSpec(name, coder, combine_fn) -> Combining value state
      spec with coder and combine_fn specified.

    Args:
      name (str): The name by which the state is identified.
      coder (Coder): Coder specifying how to encode the values to be combined.
        May be inferred.
      combine_fn (``CombineFn`` or ``callable``): Function specifying how to
        combine the values passed to state.
    """
    # Avoid circular import.
    from apache_beam.transforms.core import CombineFn

    # We want the coder to be optional, but unfortunately it comes
    # before the non-optional combine_fn parameter, which we can't
    # change for backwards compatibility reasons.
    #
    # Instead, allow it to be omitted (by either passing two arguments
    # or combine_fn by keyword.)
    if combine_fn is None:
      if coder is None:
        raise ValueError('combine_fn must be provided')
      else:
        coder, combine_fn = None, coder
    self.combine_fn = CombineFn.maybe_from_callable(combine_fn)
    # The coder here should be for the accumulator type of the given CombineFn.
    if coder is None:
      coder = self.combine_fn.get_accumulator_coder()

    super().__init__(name, coder)

  def to_runner_api(
      self, context: 'PipelineContext') -> beam_runner_api_pb2.StateSpec:
    return beam_runner_api_pb2.StateSpec(
        combining_spec=beam_runner_api_pb2.CombiningStateSpec(
            combine_fn=self.combine_fn.to_runner_api(context),
            accumulator_coder_id=context.coders.get_id(self.coder)),
        protocol=beam_runner_api_pb2.FunctionSpec(
            urn=common_urns.user_state.BAG.urn))


class OrderedListStateSpec(StateSpec):
  """Specification for a user DoFn ordered list state cell.
     Read more about OrderedListState here:
     https://beam.apache.org/documentation/programming-guide/#orderliststate
  """
  def to_runner_api(
      self, context: 'PipelineContext') -> beam_runner_api_pb2.StateSpec:
    return beam_runner_api_pb2.StateSpec(
        ordered_list_spec=beam_runner_api_pb2.OrderedListStateSpec(
            element_coder_id=context.coders.get_id(self.coder)),
        protocol=beam_runner_api_pb2.FunctionSpec(
            urn=common_urns.user_state.ORDERED_LIST.urn))


# TODO(BEAM-9562): Update Timer to have of() and clear() APIs.
Timer = NamedTuple(
    'Timer',
    [
        ('user_key', Any),
        ('dynamic_timer_tag', str),
        ('windows', tuple['windowed_value.BoundedWindow', ...]),
        ('clear_bit', bool),
        ('fire_timestamp', Optional['Timestamp']),
        ('hold_timestamp', Optional['Timestamp']),
        ('paneinfo', Optional['windowed_value.PaneInfo']),
    ])


# TODO(BEAM-9562): Plumb through actual key_coder and window_coder.
class TimerSpec(object):
  """Specification for a user stateful DoFn timer.
     Read more about Timers here:
     https://beam.apache.org/documentation/programming-guide/#timers
  """
  prefix = "ts-"

  def __init__(self, name: str, time_domain: str) -> None:
    self.name = self.prefix + name
    if time_domain not in (TimeDomain.WATERMARK, TimeDomain.REAL_TIME):
      raise ValueError('Unsupported TimeDomain: %r.' % (time_domain, ))
    self.time_domain = time_domain
    self._attached_callback: Optional[Callable] = None

  def __repr__(self) -> str:
    return '%s(%s)' % (self.__class__.__name__, self.name)

  def to_runner_api(
      self, context: 'PipelineContext', key_coder: Coder,
      window_coder: Coder) -> beam_runner_api_pb2.TimerFamilySpec:
    return beam_runner_api_pb2.TimerFamilySpec(
        time_domain=TimeDomain.to_runner_api(self.time_domain),
        timer_family_coder_id=context.coders.get_id(
            coders._TimerCoder(key_coder, window_coder)))


def on_timer(timer_spec: TimerSpec) -> Callable[[CallableT], CallableT]:
  """Decorator for timer firing DoFn method.

  This decorator allows a user to specify an on_timer processing method
  in a stateful DoFn.  Sample usage::

    class MyDoFn(DoFn):
      TIMER_SPEC = TimerSpec('timer', TimeDomain.WATERMARK)

      @on_timer(TIMER_SPEC)
      def my_timer_expiry_callback(self):
        logging.info('Timer expired!')
  """

  if not isinstance(timer_spec, TimerSpec):
    raise ValueError('@on_timer decorator expected TimerSpec.')

  def _inner(method: CallableT) -> CallableT:
    if not callable(method):
      raise ValueError('@on_timer decorator expected callable.')
    if timer_spec._attached_callback:
      raise ValueError(
          'Multiple on_timer callbacks registered for %r.' % timer_spec)
    timer_spec._attached_callback = method
    return method

  return _inner


def get_dofn_specs(dofn: 'DoFn') -> tuple[set[StateSpec], set[TimerSpec]]:
  """Gets the state and timer specs for a DoFn, if any.

  Args:
    dofn (apache_beam.transforms.core.DoFn): The DoFn instance to introspect for
      timer and state specs.
  """

  # Avoid circular import.
  from apache_beam.runners.common import MethodWrapper
  from apache_beam.transforms.core import _DoFnParam
  from apache_beam.transforms.core import _StateDoFnParam
  from apache_beam.transforms.core import _TimerDoFnParam

  all_state_specs = set()
  all_timer_specs = set()

  # Validate params to process(), start_bundle(), finish_bundle() and to
  # any on_timer callbacks.
  for method_name in dir(dofn):
    if not isinstance(getattr(dofn, method_name, None), types.MethodType):
      continue
    method = MethodWrapper(dofn, method_name)
    param_ids = [
        d.param_id for d in method.defaults if isinstance(d, _DoFnParam)
    ]
    if len(param_ids) != len(set(param_ids)):
      raise ValueError(
          'DoFn %r has duplicate %s method parameters: %s.' %
          (dofn, method_name, param_ids))
    for d in method.defaults:
      if isinstance(d, _StateDoFnParam):
        all_state_specs.add(d.state_spec)
      elif isinstance(d, _TimerDoFnParam):
        all_timer_specs.add(d.timer_spec)

  return all_state_specs, all_timer_specs


def is_stateful_dofn(dofn: 'DoFn') -> bool:
  """Determines whether a given DoFn is a stateful DoFn."""

  # A Stateful DoFn is a DoFn that uses user state or timers.
  all_state_specs, all_timer_specs = get_dofn_specs(dofn)
  return bool(all_state_specs or all_timer_specs)


def validate_stateful_dofn(dofn: 'DoFn') -> None:
  """Validates the proper specification of a stateful DoFn."""

  # Get state and timer specs.
  all_state_specs, all_timer_specs = get_dofn_specs(dofn)

  # Reject DoFns that have multiple state or timer specs with the same name.
  if len(all_state_specs) != len(set(s.name for s in all_state_specs)):
    raise ValueError(
        'DoFn %r has multiple StateSpecs with the same name: %s.' %
        (dofn, all_state_specs))
  if len(all_timer_specs) != len(set(s.name for s in all_timer_specs)):
    raise ValueError(
        'DoFn %r has multiple TimerSpecs with the same name: %s.' %
        (dofn, all_timer_specs))

  # Reject DoFns that use timer specs without corresponding timer callbacks.
  for timer_spec in all_timer_specs:
    if not timer_spec._attached_callback:
      raise ValueError((
          'DoFn %r has a TimerSpec without an associated on_timer '
          'callback: %s.') % (dofn, timer_spec))
    method_name = timer_spec._attached_callback.__name__
    if (timer_spec._attached_callback != getattr(dofn, method_name,
                                                 None).__func__):  # type: ignore[union-attr]
      raise ValueError((
          'The on_timer callback for %s is not the specified .%s method '
          'for DoFn %r (perhaps it was overwritten?).') %
                       (timer_spec, method_name, dofn))


class BaseTimer(object):
  def clear(self, dynamic_timer_tag: str = '') -> None:
    raise NotImplementedError

  def set(self, timestamp: Timestamp, dynamic_timer_tag: str = '') -> None:
    raise NotImplementedError


_TimerTuple = collections.namedtuple('timer_tuple', ('cleared', 'timestamp'))  # type: ignore[name-match]


class RuntimeTimer(BaseTimer):
  """Timer interface object passed to user code."""
  def __init__(self) -> None:
    self._timer_recordings: dict[str, _TimerTuple] = {}
    self._cleared = False
    self._new_timestamp: Optional[Timestamp] = None

  def clear(self, dynamic_timer_tag: str = '') -> None:
    self._timer_recordings[dynamic_timer_tag] = _TimerTuple(
        cleared=True, timestamp=None)

  def set(self, timestamp: Timestamp, dynamic_timer_tag: str = '') -> None:
    self._timer_recordings[dynamic_timer_tag] = _TimerTuple(
        cleared=False, timestamp=timestamp)


class RuntimeState(object):
  """State interface object passed to user code."""
  def prefetch(self) -> None:
    # The default implementation here does nothing.
    pass

  def finalize(self) -> None:
    pass


class ReadModifyWriteRuntimeState(RuntimeState):
  def read(self) -> Any:
    raise NotImplementedError(type(self))

  def write(self, value: Any) -> None:
    raise NotImplementedError(type(self))

  def clear(self) -> None:
    raise NotImplementedError(type(self))

  def commit(self) -> None:
    raise NotImplementedError(type(self))


class AccumulatingRuntimeState(RuntimeState):
  def read(self) -> Iterable[Any]:
    raise NotImplementedError(type(self))

  def add(self, value: Any) -> None:
    raise NotImplementedError(type(self))

  def clear(self) -> None:
    raise NotImplementedError(type(self))

  def commit(self) -> None:
    raise NotImplementedError(type(self))


class BagRuntimeState(AccumulatingRuntimeState):
  """Bag state interface object passed to user code.
  Read more about BagState here:
  https://beam.apache.org/documentation/programming-guide/#bagstate
  """


class SetRuntimeState(AccumulatingRuntimeState):
  """Set state interface object passed to user code.
  Read more about SetState here:
  https://beam.apache.org/documentation/programming-guide/#setstate
  """


class CombiningValueRuntimeState(AccumulatingRuntimeState):
  """Combining value state interface object passed to user code.
  Read more about CombiningValueState here:
  https://beam.apache.org/documentation/programming-guide/#combiningstate
  """


class OrderedListRuntimeState(AccumulatingRuntimeState):
  """Ordered list state interface object passed to user code.
  Read more about OrderedListState here:
  https://beam.apache.org/documentation/programming-guide/#orderliststate
  """
  def read(self) -> Iterable[tuple[Timestamp, Any]]:
    raise NotImplementedError(type(self))

  def add(self, value: tuple[Timestamp, Any]) -> None:
    raise NotImplementedError(type(self))

  def read_range(
      self, min_time_stamp: Timestamp,
      limit_time_stamp: Timestamp) -> Iterable[tuple[Timestamp, Any]]:
    raise NotImplementedError(type(self))

  def clear_range(
      self, min_time_stamp: Timestamp, limit_time_stamp: Timestamp) -> None:
    raise NotImplementedError(type(self))


class UserStateContext(object):
  """Wrapper allowing user state and timers to be accessed by a DoFnInvoker."""
  def get_timer(
      self,
      timer_spec: TimerSpec,
      key: Any,
      window: 'windowed_value.BoundedWindow',
      timestamp: Timestamp,
      pane: windowed_value.PaneInfo,
  ) -> BaseTimer:
    raise NotImplementedError(type(self))

  def get_state(
      self,
      state_spec: StateSpec,
      key: Any,
      window: 'windowed_value.BoundedWindow',
  ) -> RuntimeState:
    raise NotImplementedError(type(self))

  def commit(self) -> None:
    raise NotImplementedError(type(self))