[AIRFLOW-833] Add an airflow default_config sub-command

[gsakkis]

Dear Airflow Maintainers,

Please accept this PR that addresses the following issues:

• https://issues.apache.org/jira/browse/AIRFLOW-833

[jlowin]

I suggest that running airflow initdb creates the default config if it doesn't exist already. That way your enhancement allows a more advanced config behavior but the "basic" approach still works.

[jlowin]

This should be split into two methods, load_config_file and save_config_file. Otherwise it will be extremely confusing to figure out what it's doing when reading code.

[gsakkis]

I suggest that running airflow initdb creates the default config if it doesn't exist already. That way your enhancement allows a more advanced config behavior but the "basic" approach still works.

I'm not sure I understand what you mean here, can you elaborate? Are you suggesting to bundle the proposed functionality into airflow initdb instead of adding a new subcommand?

[jlowin]

Nope, I like the new command, I am just suggesting that in addition, the initdb function (https://github.com/apache/incubator-airflow/blob/master/airflow/utils/db.py#L102) should automatically run it if it hasn't been run already

That way the start becomes:

      pip install airflow # required
      airflow default_config # optional, only for advanced users who know they want to customize settings off the bat
      airflow initdb # required, and will generate the default if the previous command wasn't run

[gsakkis]

Ah ok, makes sense; will do!

[bolkedebruin]

Please also add unit tests that cover the new functions and updated functions.

[codecov-io]

Codecov Report

Merging #2052 into master will increase coverage by 0.01%.
The diff coverage is 89.79%.

@@            Coverage Diff             @@
##           master    #2052      +/-   ##
==========================================
+ Coverage    67.7%   67.71%   +0.01%     
==========================================
  Files         139      139              
  Lines       10579    10593      +14     
==========================================
+ Hits         7162     7173      +11     
- Misses       3417     3420       +3

Impacted Files	Coverage Δ
airflow/bin/cli.py	53.7% <100%> (+0.51%)	✅
airflow/utils/db.py	84.87% <100%> (+0.39%)	✅
airflow/www/views.py	69.63% <60%> (-0.08%)	❌
airflow/configuration.py	87% <91.17%> (+2.57%)	✅
airflow/task_runner/bash_task_runner.py	93.33% <ø> (-6.67%)	❌
airflow/utils/helpers.py	41.08% <ø> (-2.48%)	❌
airflow/models.py	86.1% <ø> (-0.06%)	❌
airflow/jobs.py	73.12% <ø> (+0.1%)	✅

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update eea5ff8...7de2eff. Read the comment docs.

[gsakkis]

All comments addressed in the new PR

[ldct]

for consistency with the rest of the commands can we name it like a verb (eg install_default_config) instead

[gsakkis]

I'm afraid I don't have the time and inclination to jump through any more hoops by an unspecified set of reviewers (presumably core contributors though I can't tell). The way this ticket and especially #2078 have been handled so far don't make me feel that "contributions are welcome and are greatly appreciated" as advertised.

Feel free to make any remaining changes you deem necessary for this PR and merge it, or not.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[gsakkis]

Bump

[ron819]

@gsakkis note that your code apply changes to the old UI which will be deprecated once #4339 is merged. It's being replaced with RABC.