#
# 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.
Experimental; no backwards-compatibility guarantees.
"""
from __future__ import absolute_import
import types
from builtins import object
from apache_beam.coders import Coder
from apache_beam.transforms.timeutil import TimeDomain
[docs]class StateSpec(object):
"""Specification for a user DoFn state cell."""
def __init__(self):
raise NotImplementedError
def __repr__(self):
return '%s(%s)' % (self.__class__.__name__, self.name)
[docs]class BagStateSpec(StateSpec):
"""Specification for a user DoFn bag state cell."""
def __init__(self, name, coder):
assert isinstance(name, str)
assert isinstance(coder, Coder)
self.name = name
self.coder = coder
[docs]class CombiningValueStateSpec(StateSpec):
"""Specification for a user DoFn combining value state cell."""
def __init__(self, name, coder, combiner):
# Avoid circular import.
from apache_beam.transforms.core import CombineFn
assert isinstance(name, str)
assert isinstance(coder, Coder)
assert isinstance(combiner, CombineFn)
self.name = name
self.coder = coder
self.combiner = combiner
[docs]class TimerSpec(object):
"""Specification for a user stateful DoFn timer."""
def __init__(self, name, time_domain):
self.name = 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 = None
def __repr__(self):
return '%s(%s)' % (self.__class__.__name__, self.name)
[docs]def on_timer(timer_spec):
"""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):
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
[docs]class UserStateUtils(object):
[docs] @staticmethod
def validate_stateful_dofn(dofn):
# 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)
# 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__):
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))