[
https://issues.apache.org/jira/browse/AIRFLOW-6529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17012711#comment-17012711
]
ASF GitHub Bot commented on AIRFLOW-6529:
-----------------------------------------
sarutak commented on pull request #7128: [AIRFLOW-6529] Serialization error
occurs when the scheduler tries to run on macOS.
URL: https://github.com/apache/airflow/pull/7128
When we try to run the scheduler on macOS, we will get a serialization error
like as follows.
```
____________ _____________
____ |__( )_________ __/__ /________ __
____ /| |_ /__ ___/_ /_ __ /_ __ \_ | /| / /
___ ___ | / _ / _ __/ _ / / /_/ /_ |/ |/ /
_/_/ |_/_/ /_/ /_/ /_/ \____/____/|__/
[2020-01-10 19:54:41,974] {executor_loader.py:59} INFO - Using executor
SequentialExecutor
[2020-01-10 19:54:41,983] {scheduler_job.py:1462} INFO - Starting the
scheduler
[2020-01-10 19:54:41,984] {scheduler_job.py:1469} INFO - Processing each
file at most -1 times
[2020-01-10 19:54:41,984] {scheduler_job.py:1472} INFO - Searching for files
in /Users/sarutak/airflow/dags
[2020-01-10 19:54:42,025] {scheduler_job.py:1474} INFO - There are 27 files
in /Users/sarutak/airflow/dags
[2020-01-10 19:54:42,025] {scheduler_job.py:1527} INFO - Resetting orphaned
tasks for active dag runs
[2020-01-10 19:54:42,059] {scheduler_job.py:1500} ERROR - Exception when
executing execute_helper
Traceback (most recent call last):
File
"/Users/sarutak/work/oss/airflow-env/master-python3.8.1/lib/python3.8/site-packages/airflow/jobs/scheduler_job.py",
line 1498, in _execute
self._execute_helper()
File
"/Users/sarutak/work/oss/airflow-env/master-python3.8.1/lib/python3.8/site-packages/airflow/jobs/scheduler_job.py",
line 1531, in _execute_helper
self.processor_agent.start()
File
"/Users/sarutak/work/oss/airflow-env/master-python3.8.1/lib/python3.8/site-packages/airflow/utils/dag_processing.py",
line 348, in start
self._process.start()
File "/opt/python/3.8.1/lib/python3.8/multiprocessing/process.py", line
121, in start
self._popen = self._Popen(self)
File "/opt/python/3.8.1/lib/python3.8/multiprocessing/context.py", line
224, in _Popen
return _default_context.get_context().Process._Popen(process_obj)
File "/opt/python/3.8.1/lib/python3.8/multiprocessing/context.py", line
283, in _Popen
return Popen(process_obj)
File
"/opt/python/3.8.1/lib/python3.8/multiprocessing/popen_spawn_posix.py", line
32, in __init__
super().__init__(process_obj)
File "/opt/python/3.8.1/lib/python3.8/multiprocessing/popen_fork.py", line
19, in __init__
self._launch(process_obj)
File
"/opt/python/3.8.1/lib/python3.8/multiprocessing/popen_spawn_posix.py", line
47, in _launch
reduction.dump(process_obj, fp)
File "/opt/python/3.8.1/lib/python3.8/multiprocessing/reduction.py", line
60, in dump
ForkingPickler(file, protocol).dump(obj)
AttributeError: Can't pickle local object
'SchedulerJob._execute.<locals>.processor_factory'
```
The reason is scheduler try to run subprocesses using multiprocessing with
spawn mode.
Actually, as of Python 3.8, spawn mode is the default mode in macOS.
---
Issue link: WILL BE INSERTED BY
[boring-cyborg](https://github.com/kaxil/boring-cyborg)
- [x] Description above provides context of the change
- [x] Commit message/PR title starts with `[AIRFLOW-NNNN]`. AIRFLOW-NNNN =
JIRA ID<sup>*</sup>
- [x] Unit tests coverage for changes (not needed for documentation changes)
- [x] Commits follow "[How to write a good git commit
message](http://chris.beams.io/posts/git-commit/)"
- [x] Relevant documentation is updated including usage instructions.
- [x] I will engage committers as explained in [Contribution Workflow
Example](https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst#contribution-workflow-example).
<sup>*</sup> For document-only changes commit message can start with
`[AIRFLOW-XXXX]`.
---
In case of fundamental code change, Airflow Improvement Proposal
([AIP](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+Improvements+Proposals))
is needed.
In case of a new dependency, check compliance with the [ASF 3rd Party
License Policy](https://www.apache.org/legal/resolved.html#category-x).
In case of backwards incompatible changes please leave a note in
[UPDATING.md](https://github.com/apache/airflow/blob/master/UPDATING.md).
Read the [Pull Request
Guidelines](https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst#pull-request-guidelines)
for more information.
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> Serialization error occurs when the scheduler tries to run on macOS.
> --------------------------------------------------------------------
>
> Key: AIRFLOW-6529
> URL: https://issues.apache.org/jira/browse/AIRFLOW-6529
> Project: Apache Airflow
> Issue Type: Bug
> Components: scheduler
> Affects Versions: 1.10.8
> Environment: macOS
> Python 3.8
> multiprocessing with spawn mode
> Reporter: Kousuke Saruta
> Assignee: Kousuke Saruta
> Priority: Major
>
> When we try to run the scheduler on macOS, we will get a serialization error
> like as follows.
> {code}
> ____________ _____________
> ____ |__( )_________ __/__ /________ __
> ____ /| |_ /__ ___/_ /_ __ /_ __ \_ | /| / /
> ___ ___ | / _ / _ __/ _ / / /_/ /_ |/ |/ /
> _/_/ |_/_/ /_/ /_/ /_/ \____/____/|__/
> [2020-01-10 19:54:41,974] {executor_loader.py:59} INFO - Using executor
> SequentialExecutor
> [2020-01-10 19:54:41,983] {scheduler_job.py:1462} INFO - Starting the
> scheduler
> [2020-01-10 19:54:41,984] {scheduler_job.py:1469} INFO - Processing each file
> at most -1 times
> [2020-01-10 19:54:41,984] {scheduler_job.py:1472} INFO - Searching for files
> in /Users/sarutak/airflow/dags
> [2020-01-10 19:54:42,025] {scheduler_job.py:1474} INFO - There are 27 files
> in /Users/sarutak/airflow/dags
> [2020-01-10 19:54:42,025] {scheduler_job.py:1527} INFO - Resetting orphaned
> tasks for active dag runs
> [2020-01-10 19:54:42,059] {scheduler_job.py:1500} ERROR - Exception when
> executing execute_helper
> Traceback (most recent call last):
> File
> "/Users/sarutak/work/oss/airflow-env/master-python3.8.1/lib/python3.8/site-packages/airflow/jobs/scheduler_job.py",
> line 1498, in _execute
> self._execute_helper()
> File
> "/Users/sarutak/work/oss/airflow-env/master-python3.8.1/lib/python3.8/site-packages/airflow/jobs/scheduler_job.py",
> line 1531, in _execute_helper
> self.processor_agent.start()
> File
> "/Users/sarutak/work/oss/airflow-env/master-python3.8.1/lib/python3.8/site-packages/airflow/utils/dag_processing.py",
> line 348, in start
> self._process.start()
> File "/opt/python/3.8.1/lib/python3.8/multiprocessing/process.py", line
> 121, in start
> self._popen = self._Popen(self)
> File "/opt/python/3.8.1/lib/python3.8/multiprocessing/context.py", line
> 224, in _Popen
> return _default_context.get_context().Process._Popen(process_obj)
> File "/opt/python/3.8.1/lib/python3.8/multiprocessing/context.py", line
> 283, in _Popen
> return Popen(process_obj)
> File
> "/opt/python/3.8.1/lib/python3.8/multiprocessing/popen_spawn_posix.py", line
> 32, in __init__
> super().__init__(process_obj)
> File "/opt/python/3.8.1/lib/python3.8/multiprocessing/popen_fork.py", line
> 19, in __init__
> self._launch(process_obj)
> File
> "/opt/python/3.8.1/lib/python3.8/multiprocessing/popen_spawn_posix.py", line
> 47, in _launch
> reduction.dump(process_obj, fp)
> File "/opt/python/3.8.1/lib/python3.8/multiprocessing/reduction.py", line
> 60, in dump
> ForkingPickler(file, protocol).dump(obj)
> AttributeError: Can't pickle local object
> 'SchedulerJob._execute.<locals>.processor_factory'
> {code}
> The reason is scheduler try to run subprocesses using multiprocessing with
> spawn mode.
> Actually, as of Python 3.8, spawn mode is the default mode in macOS.
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