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Posted to commits@airflow.apache.org by GitBox <gi...@apache.org> on 2020/10/06 14:21:42 UTC
[GitHub] [airflow] ashb opened a new pull request #11306: Prevent race condition in trying to collect result from DagFileProcessor
ashb opened a new pull request #11306:
URL: https://github.com/apache/airflow/pull/11306
A rare race condition was noticed in the Scheduler HA PR where the
"test_dags_with_system_exit" test would occasionally fail with the
following symptoms:
- The pipe was "readable" as returned by
`multiprocessing.connection.wait`
- On reading it yielded an EOFError, meaning the other side had closed
the connection
- But the process was still alive/running
This previously would result in the Manager process dying with an error.
This PR makes a few changes:
- It ensures that the pipe is simplex, not duplex (we only ever send one
data) as this is simpler
- We ensure that the "other" end of the pipe is correctly closed in both
parent and child processes. Without this the pipe would be kept open
(sometimes) until the child process had closed anyway.
- When we get an EOFError on reading and the process is still alive, we
give it a few seconds to shut down cleanly, and then kill it.
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[GitHub] [airflow] ashb merged pull request #11306: Prevent race condition in trying to collect result from DagFileProcessor
Posted by GitBox <gi...@apache.org>.
ashb merged pull request #11306:
URL: https://github.com/apache/airflow/pull/11306
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[GitHub] [airflow] ashb commented on pull request #11306: Prevent race condition in trying to collect result from DagFileProcessor
Posted by GitBox <gi...@apache.org>.
ashb commented on pull request #11306:
URL: https://github.com/apache/airflow/pull/11306#issuecomment-704303486
This is mostly only a problem for dags with `system.exit()` in it, and is made much much worse by running tests with code coverage enabled.
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[GitHub] [airflow] ashb commented on pull request #11306: Prevent race condition in trying to collect result from DagFileProcessor
Posted by GitBox <gi...@apache.org>.
ashb commented on pull request #11306:
URL: https://github.com/apache/airflow/pull/11306#issuecomment-704358553
One failure with exit 137 only. Merging.
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[GitHub] [airflow] ashb commented on pull request #11306: Prevent race condition in trying to collect result from DagFileProcessor
Posted by GitBox <gi...@apache.org>.
ashb commented on pull request #11306:
URL: https://github.com/apache/airflow/pull/11306#issuecomment-704304255
This was noticed because it started happening a lot more in #10956
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[GitHub] [airflow] ashb commented on pull request #11306: Prevent race condition in trying to collect result from DagFileProcessor
Posted by GitBox <gi...@apache.org>.
ashb commented on pull request #11306:
URL: https://github.com/apache/airflow/pull/11306#issuecomment-704313464
With extra logging in scheduler HA this was what we saw:
```
[2020-10-05 22:39:36,362] {{scheduler_job.py:298}} WARNING - TEST: EOFError received on <DagFileProcessorProcess file_path='/opt/airflow/tests/dags_with_system_exit/a_system_exit.py'>
Traceback (most recent call last):
File "/opt/airflow/airflow/jobs/scheduler_job.py", line 291, in done
self._result = self._parent_channel.recv()
File "/usr/local/lib/python3.8/multiprocessing/connection.py", line 250, in recv
buf = self._recv_bytes()
File "/usr/local/lib/python3.8/multiprocessing/connection.py", line 414, in _recv_bytes
buf = self._recv(4)
File "/usr/local/lib/python3.8/multiprocessing/connection.py", line 383, in _recv
raise EOFError
EOFError
[2020-10-05 22:39:36,364] {{scheduler_job.py:307}} WARNING - TEST: process 9709 still alive <DagFileProcessorProcess file_path='/opt/airflow/tests/dags_with_system_exit/a_system_exit.py'>
```
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