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from __future__ import absolute_import
from apache_beam import ExternalTransform
from apache_beam import pvalue
from apache_beam.coders import VarIntCoder
from apache_beam.portability.api.external_transforms_pb2 import ConfigValue
from apache_beam.portability.api.external_transforms_pb2 import ExternalConfigurationPayload
from apache_beam.transforms import ptransform
[docs]class GenerateSequence(ptransform.PTransform):
"""
An external PTransform which provides a bounded or unbounded stream of
integers.
Note: To use this transform, you need to start the Java expansion service.
Please refer to the portability documentation on how to do that. The
expansion service address has to be provided when instantiating this
transform. During pipeline translation this transform will be replaced by
the Java SDK's GenerateSequence.
If you start Flink's job server, the expansion service will be started on
port 8097. This is also the configured default for this transform. For a
different address, please set the expansion_service parameter.
For more information see:
- https://beam.apache.org/documentation/runners/flink/
- https://beam.apache.org/roadmap/portability/
Note: Runners need to support translating Read operations in order to use
this source. At the moment only the Flink Runner supports this.
Experimental; no backwards compatibility guarantees.
"""
URN = 'beam:external:java:generate_sequence:v1'
def __init__(self, start, stop=None,
elements_per_period=None, max_read_time=None,
expansion_service='localhost:8097'):
super(GenerateSequence, self).__init__()
self.start = start
self.stop = stop
self.elements_per_period = elements_per_period
self.max_read_time = max_read_time
self.expansion_service = expansion_service
[docs] def expand(self, pbegin):
if not isinstance(pbegin, pvalue.PBegin):
raise Exception("GenerateSequence must be a root transform")
coder = VarIntCoder()
coder_urn = ['beam:coder:varint:v1']
args = {
'start':
ConfigValue(
coder_urn=coder_urn,
payload=coder.encode(self.start))
}
if self.stop:
args['stop'] = ConfigValue(
coder_urn=coder_urn,
payload=coder.encode(self.stop))
if self.elements_per_period:
args['elements_per_period'] = ConfigValue(
coder_urn=coder_urn,
payload=coder.encode(self.elements_per_period))
if self.max_read_time:
args['max_read_time'] = ConfigValue(
coder_urn=coder_urn,
payload=coder.encode(self.max_read_time))
payload = ExternalConfigurationPayload(configuration=args)
return pbegin.apply(
ExternalTransform(
self.URN,
payload.SerializeToString(),
self.expansion_service))