Joar Wandborg created BEAM-7540:
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Summary: deadlock using save_main_session and logging
Key: BEAM-7540
URL: https://issues.apache.org/jira/browse/BEAM-7540
Project: Beam
Issue Type: Bug
Components: sdk-py-core
Environment: Python 3.5
Linux
apache-beam 2.12.0
Reporter: Joar Wandborg
If you set {{save_main_session = True}} and have a logging.Logger instance in
your __main__ module, calling a logger method *after* Pipeline.run has been
called, the process will hang and never exit.
Python 3 Pipeline that reproduces the error:
{code}
import logging
import apache_beam as beam
from apache_beam.options.pipeline_options import PipelineOptions, SetupOptions
_log = logging.getLogger(__name__)
def main(argv=None):
logging.basicConfig(level=logging.INFO)
pipeline_options = PipelineOptions(argv)
setup_options = pipeline_options.view_as(SetupOptions) # type: SetupOptions
setup_options.save_main_session = True
_log.info("Running pipeline")
with beam.Pipeline(runner="DirectRunner", options=pipeline_options) as p:
p | beam.Create(["hello", "world"]) | beam.Map(lambda x: print(x))
print("""
Call to _log.info will now deadlock, since the logging handler's
threading.RLock() has been passed through dill.
When you press Ctrl-C, the traceback should confirm that the process is
stuck at:
File "/usr/lib/python3.5/logging/__init__.py", line 810, in acquire
self.lock.acquire()
""")
_log.info("Pipeline done")
print("Launching nukes")
if __name__ == '__main__':
main()
{code}
I have opened an issue with {{dill}} as well:
https://github.com/uqfoundation/dill/issues/321
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