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https://issues.apache.org/jira/browse/BEAM-1630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16275284#comment-16275284
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ASF GitHub Bot commented on BEAM-1630:
--------------------------------------
chamikaramj commented on a change in pull request #4064: [BEAM-1630] Adds
support for processing Splittable DoFns using DirectRunner.
URL: https://github.com/apache/beam/pull/4064#discussion_r154452810
##########
File path: sdks/python/apache_beam/runners/sdf_common.py
##########
@@ -0,0 +1,161 @@
+#
+# 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.
+#
+
+"""This module contains Splittable DoFn logic that's common to all runners."""
+
+import uuid
+
+import apache_beam as beam
+from apache_beam import pvalue
+from apache_beam.coders import typecoders
+from apache_beam.pipeline import AppliedPTransform
+from apache_beam.pipeline import PTransformOverride
+from apache_beam.runners.common import DoFnInvoker
+from apache_beam.runners.common import DoFnSignature
+from apache_beam.transforms.core import ParDo
+from apache_beam.transforms.ptransform import PTransform
+
+
+class SplittableParDoOverride(PTransformOverride):
+ """A transform override for ParDo transformss of SplittableDoFns.
+
+ Replaces the ParDo transform with a SplittableParDo transform that performs
+ SDF specific logic.
+ """
+
+ def get_matcher(self):
+ def _matcher(applied_ptransform):
+ assert isinstance(applied_ptransform, AppliedPTransform)
+ transform = applied_ptransform.transform
+ if isinstance(transform, ParDo):
+ signature = DoFnSignature(transform.fn)
+ return signature.is_splittable_dofn()
+
+ return _matcher
+
+ def get_replacement_transform(self, ptransform):
+ assert isinstance(ptransform, ParDo)
+ do_fn = ptransform.fn
+ signature = DoFnSignature(do_fn)
+ if signature.is_splittable_dofn():
+ return SplittableParDo(ptransform)
+ else:
+ return ptransform
+
+
+class SplittableParDo(PTransform):
+ """A transform that processes a PCollection using a Splittable DoFn."""
+
+ def __init__(self, ptransform):
+ assert isinstance(ptransform, ParDo)
+ self._ptransform = ptransform
+
+ def expand(self, pcoll):
+ sdf = self._ptransform.fn
+ signature = DoFnSignature(sdf)
+ invoker = DoFnInvoker.create_invoker(signature, process_invocation=False)
+
+ element_coder = typecoders.registry.get_coder(pcoll.element_type)
+ restriction_coder = invoker.invoke_restriction_coder()
+
+ keyed_elements = (pcoll
+ | 'pair' >> ParDo(PairWithRestrictionFn(sdf))
+ | 'split' >> ParDo(SplitRestrictionFn(sdf))
+ | 'explode' >> ParDo(ExplodeWindowsFn())
+ | 'random' >> ParDo(RandomUniqueKeyFn()))
+
+ return keyed_elements | ProcessKeyedElements(
+ sdf, element_coder, restriction_coder,
+ pcoll.windowing, self._ptransform.args, self._ptransform.kwargs)
+
+
+class ElementAndRestriction(object):
+ """A holder for an element and a restriction."""
+
+ def __init__(self, element, restriction):
+ self.element = element
+ self.restriction = restriction
+
+
+class PairWithRestrictionFn(beam.DoFn):
+ """A transform that pairs each element with a restriction."""
+
+ def __init__(self, do_fn):
+ signature = DoFnSignature(do_fn)
+ self._invoker = DoFnInvoker.create_invoker(
+ signature, process_invocation=False)
+
+ def process(self, element, window=beam.DoFn.WindowParam, *args, **kwargs):
+ initial_restriction = self._invoker.invoke_initial_restriction(element)
+ yield ElementAndRestriction(element, initial_restriction)
+
+
+class SplitRestrictionFn(beam.DoFn):
+ """A transform that perform initial splitting of Splittable DoFn inputs."""
+
+ def __init__(self, do_fn):
+ signature = DoFnSignature(do_fn)
+ self._invoker = DoFnInvoker.create_invoker(
+ signature, process_invocation=False)
+
+ def process(self, element_and_restriction, *args, **kwargs):
+ element = element_and_restriction.element
+ restriction = element_and_restriction.restriction
+ restriction_parts = self._invoker.invoke_split(
+ element,
+ restriction)
+ for part in restriction_parts:
+ yield ElementAndRestriction(element, part)
+
+
+class ExplodeWindowsFn(beam.DoFn):
+ """A transform that forces the runner to explode windows.
+
+ This is done to make sure that Splittable DoFn proceses an element for each
of
+ the windows that element belongs to.
+ """
+
+ def process(self, element, window=beam.DoFn.WindowParam, *args, **kwargs):
+ yield element
+
+
+class RandomUniqueKeyFn(beam.DoFn):
+ """A transform that assigns a unique key to each element."""
+
+ def process(self, element, window=beam.DoFn.WindowParam, *args, **kwargs):
+ yield (uuid.uuid4().bytes, element)
Review comment:
Added TODOs to here and iobase._WriteBundleDoFn. I think collisions are
extremely rare for uuid.uuid4() though. Also, added an assertion to force a
failure here if a collision is detected.
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> Add Splittable DoFn to Python SDK
> ---------------------------------
>
> Key: BEAM-1630
> URL: https://issues.apache.org/jira/browse/BEAM-1630
> Project: Beam
> Issue Type: Improvement
> Components: sdk-py-core
> Reporter: Chamikara Jayalath
> Assignee: Chamikara Jayalath
>
> Splittable DoFn [1] is currently being implemented for Java SDK [2]. We
> should add this to Python SDK as well.
> Following document proposes an API for this.
> https://docs.google.com/document/d/1h_zprJrOilivK2xfvl4L42vaX4DMYGfH1YDmi-s_ozM/edit?usp=sharing
> [1] https://s.apache.org/splittable-do-fn
> [2]
> https://lists.apache.org/thread.html/0ce61ac162460a149d5c93cdface37cc383f8030fe86ca09e5699b18@%3Cdev.beam.apache.org%3E
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