Apache Beam Dataflow: 'NoneType' object has no attribute 'parts' - google-bigquery

Question

I'm trying to write a pipeline to read a stream from pubsub and write it to bigquery using google cloud dataflow with apache beam.
I have this code:
import apache_beam as beam
from apache_beam.transforms.window import FixedWindows
topic = 'projects/???/topics/???'
table = '???.???'
gcs_path = "gs://???"
with beam.Pipeline(runner="DataflowRunner", argv=[
"--project", "???",
"--staging_location", ("%s/staging_location" % gcs_path),
"--temp_location", ("%s/temp" % gcs_path),
"--output", ("%s/output" % gcs_path)
]) as p:
(p
| 'winderow' >> beam.WindowInto(FixedWindows(60))
| 'hello' >> beam.io.gcp.pubsub.ReadStringsFromPubSub(topic)
| 'hello2' >> beam.io.Write(beam.io.gcp.bigquery.BigQuerySink(table))
)
p.run().wait_until_finish()
But I'm getting this error when running it:
No handlers could be found for logger "oauth2client.contrib.multistore_file"
ERROR:root:Error while visiting winderow
Traceback (most recent call last):
File ".\main.py", line 20, in <module>
p.run().wait_until_finish()
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\pipeline.py", line 339, in run
return self.runner.run(self)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\runners\dataflow\dataflow_runner.py", line 296, in run
super(DataflowRunner, self).run(pipeline)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\runners\runner.py", line 138, in run
pipeline.visit(RunVisitor(self))
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\pipeline.py", line 367, in visit
self._root_transform().visit(visitor, self, visited)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\pipeline.py", line 710, in visit
part.visit(visitor, pipeline, visited)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\pipeline.py", line 713, in visit
visitor.visit_transform(self)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\runners\runner.py", line 133, in visit_transform
self.runner.run_transform(transform_node)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\runners\runner.py", line 176, in run_transform
return m(transform_node)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\runners\dataflow\dataflow_runner.py", line 526, in run_ParDo
input_step = self._cache.get_pvalue(transform_node.inputs[0])
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\runners\runner.py", line 252, in get_pvalue
self._ensure_pvalue_has_real_producer(pvalue)
File "C:\ProgramData\Anaconda2\lib\site-packages\apache_beam\runners\runner.py", line 226, in _ensure_pvalue_has_real_producer
while real_producer.parts:
AttributeError: 'NoneType' object has no attribute 'parts'
Is this a problem with the code or configuration?
How can I get it working?

Answer 1

I don't have experience with windowed pipelines yet but for what I understand from the concept, the windows are supposed to be applied to your input data and not as a pipeline setup.
This being the case, your code probably should be:
with beam.Pipeline(runner="DataflowRunner", argv=[
"--project", "???",
"--staging_location", ("%s/staging_location" % gcs_path),
"--temp_location", ("%s/temp" % gcs_path),
"--output", ("%s/output" % gcs_path)
]) as p:
(p
| 'hello' >> beam.io.gcp.pubsub.ReadStringsFromPubSub(topic)
| 'winderow' >> beam.WindowInto(FixedWindows(60))
| 'hello2' >> beam.io.Write(beam.io.gcp.bigquery.BigQuerySink(table))
)
p.run().wait_until_finish()
The official repo have some samples on windowed operations as well.