def _check_fn_registration_multi_request(self, *args):
"""Check the function registration calls to the sdk_harness.
Args:
tuple of request_count, number of process_bundles per request and workers
counts to process the request.
"""
for (request_count, process_bundles_per_request) in args:
requests = []
process_bundle_descriptors = []
for i in range(request_count):
pbd = self._get_process_bundles(i, process_bundles_per_request)
process_bundle_descriptors.extend(pbd)
requests.append(
beam_fn_api_pb2.InstructionRequest(
instruction_id=str(i),
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=process_bundle_descriptors)))
test_controller = BeamFnControlServicer(requests)
server = grpc.server(UnboundedThreadPoolExecutor())
beam_fn_api_pb2_grpc.add_BeamFnControlServicer_to_server(
test_controller, server)
test_port = server.add_insecure_port("[::]:0")
server.start()
harness = sdk_worker.SdkHarness(
"localhost:%s" % test_port, state_cache_size=100)
harness.run()
self.assertEqual(harness._bundle_processor_cache.fns,
{item.id: item
for item in process_bundle_descriptors})
def test_fn_registration(self):
process_bundle_descriptors = [
beam_fn_api_pb2.ProcessBundleDescriptor(
id=str(100 + ix),
transforms={
str(ix):
beam_runner_api_pb2.PTransform(unique_name=str(ix))
}) for ix in range(4)
]
test_controller = BeamFnControlServicer([
beam_fn_api_pb2.InstructionRequest(
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=process_bundle_descriptors))
])
server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
beam_fn_api_pb2.add_BeamFnControlServicer_to_server(
test_controller, server)
test_port = server.add_insecure_port("[::]:0")
server.start()
channel = grpc.insecure_channel("localhost:%s" % test_port)
harness = sdk_worker.SdkHarness(channel)
harness.run()
self.assertEqual(
harness.worker.fns,
{item.id: item
for item in process_bundle_descriptors})
def test_source_split(self):
source = RangeSource(0, 100)
expected_splits = list(source.split(30))
worker = sdk_harness.SdkWorker(
None, data_plane.GrpcClientDataChannelFactory())
worker.register(
beam_fn_api_pb2.RegisterRequest(process_bundle_descriptor=[
beam_fn_api_pb2.ProcessBundleDescriptor(primitive_transform=[
beam_fn_api_pb2.PrimitiveTransform(
function_spec=sdk_harness.serialize_and_pack_py_fn(
SourceBundle(1.0, source, None, None),
sdk_harness.PYTHON_SOURCE_URN,
id="src"))
])
]))
split_response = worker.initial_source_split(
beam_fn_api_pb2.InitialSourceSplitRequest(
desired_bundle_size_bytes=30, source_reference="src"))
self.assertEqual(expected_splits, [
sdk_harness.unpack_and_deserialize_py_fn(s.source)
for s in split_response.splits
])
self.assertEqual([s.weight for s in expected_splits],
[s.relative_size for s in split_response.splits])
def test_fn_registration(self):
fns = [beam_fn_api_pb2.FunctionSpec(id=str(ix)) for ix in range(4)]
process_bundle_descriptors = [
beam_fn_api_pb2.ProcessBundleDescriptor(
id=str(100 + ix),
primitive_transform=[
beam_fn_api_pb2.PrimitiveTransform(function_spec=fn)
]) for ix, fn in enumerate(fns)
]
test_controller = BeamFnControlServicer([
beam_fn_api_pb2.InstructionRequest(
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=process_bundle_descriptors))
])
server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
beam_fn_api_pb2.add_BeamFnControlServicer_to_server(
test_controller, server)
test_port = server.add_insecure_port("[::]:0")
server.start()
channel = grpc.insecure_channel("localhost:%s" % test_port)
harness = sdk_worker.SdkHarness(channel)
harness.run()
self.assertEqual(
harness.worker.fns,
{item.id: item
for item in fns + process_bundle_descriptors})
def process_bundle(self, inputs, expected_outputs):
# Unique id for the instruction processing this bundle.
BundleManager._uid_counter += 1
process_bundle_id = 'bundle_%s' % BundleManager._uid_counter
# Register the bundle descriptor, if needed.
if self._registered:
registration_future = None
else:
process_bundle_registration = beam_fn_api_pb2.InstructionRequest(
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=[self._bundle_descriptor]))
registration_future = self._controller.control_handler.push(
process_bundle_registration)
self._registered = True
# Write all the input data to the channel.
for (transform_id, name), elements in inputs.items():
data_out = self._controller.data_plane_handler.output_stream(
process_bundle_id, beam_fn_api_pb2.Target(
primitive_transform_reference=transform_id, name=name))
for element_data in elements:
data_out.write(element_data)
data_out.close()
# Actually start the bundle.
if registration_future and registration_future.get().error:
raise RuntimeError(registration_future.get().error)
process_bundle = beam_fn_api_pb2.InstructionRequest(
instruction_id=process_bundle_id,
process_bundle=beam_fn_api_pb2.ProcessBundleRequest(
process_bundle_descriptor_reference=self._bundle_descriptor.id))
result_future = self._controller.control_handler.push(process_bundle)
with ProgressRequester(
self._controller, process_bundle_id, self._progress_frequency):
# Gather all output data.
expected_targets = [
beam_fn_api_pb2.Target(primitive_transform_reference=transform_id,
name=output_name)
for (transform_id, output_name), _ in expected_outputs.items()]
logging.debug('Gather all output data from %s.', expected_targets)
for output in self._controller.data_plane_handler.input_elements(
process_bundle_id,
expected_targets,
abort_callback=lambda: (result_future.is_done()
and result_future.get().error)):
target_tuple = (
output.target.primitive_transform_reference, output.target.name)
if target_tuple in expected_outputs:
self._get_buffer(expected_outputs[target_tuple]).append(output.data)
logging.debug('Wait for the bundle to finish.')
result = result_future.get()
if result.error:
raise RuntimeError(result.error)
return result
def _map_task_registration(self, map_task, state_handler,
data_operation_spec):
input_data, side_input_data, runner_sinks, process_bundle_descriptor = (
self._map_task_to_protos(map_task, data_operation_spec))
# Side inputs will be accessed over the state API.
for key, elements_data in side_input_data.items():
state_key = beam_fn_api_pb2.StateKey.MultimapSideInput(key=key)
state_handler.Clear(state_key)
state_handler.Append(state_key, [elements_data])
return beam_fn_api_pb2.InstructionRequest(
instruction_id=self._next_uid(),
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=[process_bundle_descriptor])
), runner_sinks, input_data
def _register_bundle_descriptor(self):
# type: () -> Optional[ControlFuture]
if self._registered:
registration_future = None
else:
assert self._worker_handler is not None
process_bundle_registration = beam_fn_api_pb2.InstructionRequest(
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=[self._bundle_descriptor]))
registration_future = self._worker_handler.control_conn.push(
process_bundle_registration)
self._registered = True
return registration_future
def test_source_split_via_instruction(self):
source = RangeSource(0, 100)
expected_splits = list(source.split(30))
test_controller = BeamFnControlServicer([
beam_fn_api_pb2.InstructionRequest(
instruction_id="register_request",
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=[
beam_fn_api_pb2.ProcessBundleDescriptor(
primitive_transform=[
beam_fn_api_pb2.PrimitiveTransform(
function_spec=sdk_harness.
serialize_and_pack_py_fn(
SourceBundle(1.0, source, None, None),
sdk_harness.PYTHON_SOURCE_URN,
id="src"))
])
])),
beam_fn_api_pb2.InstructionRequest(
instruction_id="split_request",
initial_source_split=beam_fn_api_pb2.InitialSourceSplitRequest(
desired_bundle_size_bytes=30, source_reference="src"))
])
server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
beam_fn_api_pb2.add_BeamFnControlServicer_to_server(
test_controller, server)
test_port = server.add_insecure_port("[::]:0")
server.start()
channel = grpc.insecure_channel("localhost:%s" % test_port)
harness = sdk_harness.SdkHarness(channel)
harness.run()
split_response = test_controller.responses[
"split_request"].initial_source_split
self.assertEqual(expected_splits, [
sdk_harness.unpack_and_deserialize_py_fn(s.source)
for s in split_response.splits
])
self.assertEqual([s.weight for s in expected_splits],
[s.relative_size for s in split_response.splits])
def run_stage(self, controller, pipeline_components, stage, pcoll_buffers,
safe_coders):
context = pipeline_context.PipelineContext(pipeline_components)
data_operation_spec = controller.data_operation_spec()
def extract_endpoints(stage):
# Returns maps of transform names to PCollection identifiers.
# Also mutates IO stages to point to the data data_operation_spec.
data_input = {}
data_side_input = {}
data_output = {}
for transform in stage.transforms:
if transform.spec.urn in (bundle_processor.DATA_INPUT_URN,
bundle_processor.DATA_OUTPUT_URN):
pcoll_id = transform.spec.payload
if transform.spec.urn == bundle_processor.DATA_INPUT_URN:
target = transform.unique_name, only_element(
transform.outputs)
data_input[target] = pcoll_id
elif transform.spec.urn == bundle_processor.DATA_OUTPUT_URN:
target = transform.unique_name, only_element(
transform.inputs)
data_output[target] = pcoll_id
else:
raise NotImplementedError
if data_operation_spec:
transform.spec.payload = data_operation_spec.SerializeToString(
)
else:
transform.spec.payload = ""
elif transform.spec.urn == urns.PARDO_TRANSFORM:
payload = proto_utils.parse_Bytes(
transform.spec.payload,
beam_runner_api_pb2.ParDoPayload)
for tag, si in payload.side_inputs.items():
data_side_input[transform.unique_name, tag] = (
'materialize:' + transform.inputs[tag],
beam.pvalue.SideInputData.from_runner_api(
si, None))
return data_input, data_side_input, data_output
logging.info('Running %s', stage.name)
logging.debug(' %s', stage)
data_input, data_side_input, data_output = extract_endpoints(stage)
process_bundle_descriptor = beam_fn_api_pb2.ProcessBundleDescriptor(
id=self._next_uid(),
transforms={
transform.unique_name: transform
for transform in stage.transforms
},
pcollections=dict(pipeline_components.pcollections.items()),
coders=dict(pipeline_components.coders.items()),
windowing_strategies=dict(
pipeline_components.windowing_strategies.items()),
environments=dict(pipeline_components.environments.items()))
process_bundle_registration = beam_fn_api_pb2.InstructionRequest(
instruction_id=self._next_uid(),
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=[process_bundle_descriptor]))
process_bundle = beam_fn_api_pb2.InstructionRequest(
instruction_id=self._next_uid(),
process_bundle=beam_fn_api_pb2.ProcessBundleRequest(
process_bundle_descriptor_reference=process_bundle_descriptor.
id))
# Write all the input data to the channel.
for (transform_id, name), pcoll_id in data_input.items():
data_out = controller.data_plane_handler.output_stream(
process_bundle.instruction_id,
beam_fn_api_pb2.Target(
primitive_transform_reference=transform_id, name=name))
for element_data in pcoll_buffers[pcoll_id]:
data_out.write(element_data)
data_out.close()
# Store the required side inputs into state.
for (transform_id, tag), (pcoll_id, si) in data_side_input.items():
elements_by_window = _WindowGroupingBuffer(si)
for element_data in pcoll_buffers[pcoll_id]:
elements_by_window.append(element_data)
for window, elements_data in elements_by_window.items():
state_key = beam_fn_api_pb2.StateKey(
multimap_side_input=beam_fn_api_pb2.StateKey.
MultimapSideInput(ptransform_id=transform_id,
side_input_id=tag,
window=window))
controller.state_handler.blocking_append(
state_key, elements_data, process_bundle.instruction_id)
# Register and start running the bundle.
logging.debug('Register and start running the bundle')
controller.control_handler.push(process_bundle_registration)
controller.control_handler.push(process_bundle)
# Wait for the bundle to finish.
logging.debug('Wait for the bundle to finish.')
while True:
result = controller.control_handler.pull()
if result and result.instruction_id == process_bundle.instruction_id:
if result.error:
raise RuntimeError(result.error)
break
expected_targets = [
beam_fn_api_pb2.Target(primitive_transform_reference=transform_id,
name=output_name)
for (transform_id, output_name), _ in data_output.items()
]
# Gather all output data.
logging.debug('Gather all output data from %s.', expected_targets)
for output in controller.data_plane_handler.input_elements(
process_bundle.instruction_id, expected_targets):
target_tuple = (output.target.primitive_transform_reference,
output.target.name)
if target_tuple in data_output:
pcoll_id = data_output[target_tuple]
if pcoll_id.startswith('materialize:'):
# Just store the data chunks for replay.
pcoll_buffers[pcoll_id].append(output.data)
elif pcoll_id.startswith('group:'):
# This is a grouping write, create a grouping buffer if needed.
if pcoll_id not in pcoll_buffers:
original_gbk_transform = pcoll_id.split(':', 1)[1]
transform_proto = pipeline_components.transforms[
original_gbk_transform]
input_pcoll = only_element(
transform_proto.inputs.values())
output_pcoll = only_element(
transform_proto.outputs.values())
pre_gbk_coder = context.coders[
safe_coders[pipeline_components.
pcollections[input_pcoll].coder_id]]
post_gbk_coder = context.coders[
safe_coders[pipeline_components.
pcollections[output_pcoll].coder_id]]
windowing_strategy = context.windowing_strategies[
pipeline_components.pcollections[output_pcoll].
windowing_strategy_id]
pcoll_buffers[pcoll_id] = _GroupingBuffer(
pre_gbk_coder, post_gbk_coder, windowing_strategy)
pcoll_buffers[pcoll_id].append(output.data)
else:
# These should be the only two identifiers we produce for now,
# but special side input writes may go here.
raise NotImplementedError(pcoll_id)
return result
def _map_task_registration(self, map_task, state_handler,
data_operation_spec):
input_data = {}
runner_sinks = {}
transforms = []
transform_index_to_id = {}
# Maps coders to new coder objects and references.
coders = {}
def coder_id(coder):
if coder not in coders:
coders[coder] = beam_fn_api_pb2.Coder(
function_spec=sdk_worker.pack_function_spec_data(
json.dumps(coder.as_cloud_object()),
sdk_worker.PYTHON_CODER_URN,
id=self._next_uid()))
return coders[coder].function_spec.id
def output_tags(op):
return getattr(op, 'output_tags', ['out'])
def as_target(op_input):
input_op_index, input_output_index = op_input
input_op = map_task[input_op_index][1]
return {
'ignored_input_tag':
beam_fn_api_pb2.Target.List(target=[
beam_fn_api_pb2.Target(
primitive_transform_reference=transform_index_to_id[
input_op_index],
name=output_tags(input_op)[input_output_index])
])
}
def outputs(op):
return {
tag:
beam_fn_api_pb2.PCollection(coder_reference=coder_id(coder))
for tag, coder in zip(output_tags(op), op.output_coders)
}
for op_ix, (stage_name, operation) in enumerate(map_task):
transform_id = transform_index_to_id[op_ix] = self._next_uid()
if isinstance(operation, operation_specs.WorkerInMemoryWrite):
# Write this data back to the runner.
fn = beam_fn_api_pb2.FunctionSpec(
urn=sdk_worker.DATA_OUTPUT_URN, id=self._next_uid())
if data_operation_spec:
fn.data.Pack(data_operation_spec)
inputs = as_target(operation.input)
side_inputs = {}
runner_sinks[(transform_id, 'out')] = operation
elif isinstance(operation, operation_specs.WorkerRead):
# A Read is either translated to a direct injection of windowed values
# into the sdk worker, or an injection of the source object into the
# sdk worker as data followed by an SDF that reads that source.
if (isinstance(operation.source.source,
maptask_executor_runner.InMemorySource)
and isinstance(
operation.source.source.default_output_coder(),
WindowedValueCoder)):
output_stream = create_OutputStream()
element_coder = (operation.source.source.
default_output_coder().get_impl())
# Re-encode the elements in the nested context and
# concatenate them together
for element in operation.source.source.read(None):
element_coder.encode_to_stream(element, output_stream,
True)
target_name = self._next_uid()
input_data[(transform_id,
target_name)] = output_stream.get()
fn = beam_fn_api_pb2.FunctionSpec(
urn=sdk_worker.DATA_INPUT_URN, id=self._next_uid())
if data_operation_spec:
fn.data.Pack(data_operation_spec)
inputs = {target_name: beam_fn_api_pb2.Target.List()}
side_inputs = {}
else:
# Read the source object from the runner.
source_coder = beam.coders.DillCoder()
input_transform_id = self._next_uid()
output_stream = create_OutputStream()
source_coder.get_impl().encode_to_stream(
GlobalWindows.windowed_value(operation.source),
output_stream, True)
target_name = self._next_uid()
input_data[(input_transform_id,
target_name)] = output_stream.get()
input_ptransform = beam_fn_api_pb2.PrimitiveTransform(
id=input_transform_id,
function_spec=beam_fn_api_pb2.FunctionSpec(
urn=sdk_worker.DATA_INPUT_URN,
id=self._next_uid()),
# TODO(robertwb): Possible name collision.
step_name=stage_name + '/inject_source',
inputs={target_name: beam_fn_api_pb2.Target.List()},
outputs={
'out':
beam_fn_api_pb2.PCollection(
coder_reference=coder_id(source_coder))
})
if data_operation_spec:
input_ptransform.function_spec.data.Pack(
data_operation_spec)
transforms.append(input_ptransform)
# Read the elements out of the source.
fn = sdk_worker.pack_function_spec_data(
OLDE_SOURCE_SPLITTABLE_DOFN_DATA,
sdk_worker.PYTHON_DOFN_URN,
id=self._next_uid())
inputs = {
'ignored_input_tag':
beam_fn_api_pb2.Target.List(target=[
beam_fn_api_pb2.Target(
primitive_transform_reference=
input_transform_id,
name='out')
])
}
side_inputs = {}
elif isinstance(operation, operation_specs.WorkerDoFn):
fn = sdk_worker.pack_function_spec_data(
operation.serialized_fn,
sdk_worker.PYTHON_DOFN_URN,
id=self._next_uid())
inputs = as_target(operation.input)
# Store the contents of each side input for state access.
for si in operation.side_inputs:
assert isinstance(si.source, iobase.BoundedSource)
element_coder = si.source.default_output_coder()
view_id = self._next_uid()
# TODO(robertwb): Actually flesh out the ViewFn API.
side_inputs[si.tag] = beam_fn_api_pb2.SideInput(
view_fn=sdk_worker.serialize_and_pack_py_fn(
element_coder,
urn=sdk_worker.PYTHON_ITERABLE_VIEWFN_URN,
id=view_id))
# Re-encode the elements in the nested context and
# concatenate them together
output_stream = create_OutputStream()
for element in si.source.read(
si.source.get_range_tracker(None, None)):
element_coder.get_impl().encode_to_stream(
element, output_stream, True)
elements_data = output_stream.get()
state_key = beam_fn_api_pb2.StateKey.MultimapSideInput(
key=view_id)
state_handler.Clear(state_key)
state_handler.Append(state_key, elements_data)
elif isinstance(operation, operation_specs.WorkerFlatten):
fn = sdk_worker.pack_function_spec_data(
operation.serialized_fn,
sdk_worker.IDENTITY_DOFN_URN,
id=self._next_uid())
inputs = {
'ignored_input_tag':
beam_fn_api_pb2.Target.List(target=[
beam_fn_api_pb2.Target(
primitive_transform_reference=
transform_index_to_id[input_op_index],
name=output_tags(map_task[input_op_index]
[1])[input_output_index]) for
input_op_index, input_output_index in operation.inputs
])
}
side_inputs = {}
else:
raise TypeError(operation)
ptransform = beam_fn_api_pb2.PrimitiveTransform(
id=transform_id,
function_spec=fn,
step_name=stage_name,
inputs=inputs,
side_inputs=side_inputs,
outputs=outputs(operation))
transforms.append(ptransform)
process_bundle_descriptor = beam_fn_api_pb2.ProcessBundleDescriptor(
id=self._next_uid(),
coders=coders.values(),
primitive_transform=transforms)
return beam_fn_api_pb2.InstructionRequest(
instruction_id=self._next_uid(),
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=[process_bundle_descriptor
])), runner_sinks, input_data
def run_stage(
self, controller, pipeline_components, stage, pcoll_buffers, safe_coders):
coders = pipeline_context.PipelineContext(pipeline_components).coders
data_operation_spec = controller.data_operation_spec()
def extract_endpoints(stage):
# Returns maps of transform names to PCollection identifiers.
# Also mutates IO stages to point to the data data_operation_spec.
data_input = {}
data_side_input = {}
data_output = {}
for transform in stage.transforms:
pcoll_id = transform.spec.payload
if transform.spec.urn in (bundle_processor.DATA_INPUT_URN,
bundle_processor.DATA_OUTPUT_URN):
if transform.spec.urn == bundle_processor.DATA_INPUT_URN:
target = transform.unique_name, only_element(transform.outputs)
data_input[target] = pcoll_id
elif transform.spec.urn == bundle_processor.DATA_OUTPUT_URN:
target = transform.unique_name, only_element(transform.inputs)
data_output[target] = pcoll_id
else:
raise NotImplementedError
if data_operation_spec:
transform.spec.payload = data_operation_spec.SerializeToString()
transform.spec.any_param.Pack(data_operation_spec)
else:
transform.spec.payload = ""
transform.spec.any_param.Clear()
return data_input, data_side_input, data_output
logging.info('Running %s', stage.name)
logging.debug(' %s', stage)
data_input, data_side_input, data_output = extract_endpoints(stage)
if data_side_input:
raise NotImplementedError('Side inputs.')
process_bundle_descriptor = beam_fn_api_pb2.ProcessBundleDescriptor(
id=self._next_uid(),
transforms={transform.unique_name: transform
for transform in stage.transforms},
pcollections=dict(pipeline_components.pcollections.items()),
coders=dict(pipeline_components.coders.items()),
windowing_strategies=dict(
pipeline_components.windowing_strategies.items()),
environments=dict(pipeline_components.environments.items()))
process_bundle_registration = beam_fn_api_pb2.InstructionRequest(
instruction_id=self._next_uid(),
register=beam_fn_api_pb2.RegisterRequest(
process_bundle_descriptor=[process_bundle_descriptor]))
process_bundle = beam_fn_api_pb2.InstructionRequest(
instruction_id=self._next_uid(),
process_bundle=beam_fn_api_pb2.ProcessBundleRequest(
process_bundle_descriptor_reference=
process_bundle_descriptor.id))
# Write all the input data to the channel.
for (transform_id, name), pcoll_id in data_input.items():
data_out = controller.data_plane_handler.output_stream(
process_bundle.instruction_id, beam_fn_api_pb2.Target(
primitive_transform_reference=transform_id, name=name))
for element_data in pcoll_buffers[pcoll_id]:
data_out.write(element_data)
data_out.close()
# Register and start running the bundle.
controller.control_handler.push(process_bundle_registration)
controller.control_handler.push(process_bundle)
# Wait for the bundle to finish.
while True:
result = controller.control_handler.pull()
if result and result.instruction_id == process_bundle.instruction_id:
if result.error:
raise RuntimeError(result.error)
break
# Gather all output data.
expected_targets = [
beam_fn_api_pb2.Target(primitive_transform_reference=transform_id,
name=output_name)
for (transform_id, output_name), _ in data_output.items()]
for output in controller.data_plane_handler.input_elements(
process_bundle.instruction_id, expected_targets):
target_tuple = (
output.target.primitive_transform_reference, output.target.name)
if target_tuple in data_output:
pcoll_id = data_output[target_tuple]
if pcoll_id.startswith('materialize:'):
# Just store the data chunks for replay.
pcoll_buffers[pcoll_id].append(output.data)
elif pcoll_id.startswith('group:'):
# This is a grouping write, create a grouping buffer if needed.
if pcoll_id not in pcoll_buffers:
original_gbk_transform = pcoll_id.split(':', 1)[1]
transform_proto = pipeline_components.transforms[
original_gbk_transform]
input_pcoll = only_element(transform_proto.inputs.values())
output_pcoll = only_element(transform_proto.outputs.values())
pre_gbk_coder = coders[safe_coders[
pipeline_components.pcollections[input_pcoll].coder_id]]
post_gbk_coder = coders[safe_coders[
pipeline_components.pcollections[output_pcoll].coder_id]]
pcoll_buffers[pcoll_id] = _GroupingBuffer(
pre_gbk_coder, post_gbk_coder)
pcoll_buffers[pcoll_id].append(output.data)
else:
# These should be the only two identifiers we produce for now,
# but special side input writes may go here.
raise NotImplementedError(pcoll_id)
