[AIRFLOW-6192] Stop creating Hook from SFTPSensor.__init__

[kaxil]

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Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-6192

Description

• Here are some details about my PR, including screenshots of any UI changes:
  From Slack (https://apache-airflow.slack.com/archives/CCQ7EGB1P/p1575647500146200):

When I create a task based upon the SFTPSensor and then parse the Python file, do I see two log entries coming from base_hook.py referencing the default sftp connection id? I also see the same log messages whenever the DAGs are refreshed.

airflow@0030a4ae49df:~$ python dags/sftp_sensor.py
[2019-12-06 15:45:16,440] settings.py:252 INFO - settings.configure_orm(): Using pool settings. pool_size=5, max_overflow=10, pool_recycle=1800, pid=9685
/usr/local/lib/python3.7/site-packages/psycopg2/_init_.py:144: UserWarning: The psycopg2 wheel package will be renamed from release 2.8; in order to keep installing from binary please use "pip install psycopg2-binary" instead. For details see: <http://initd.org/psycopg/docs/install.html#binary-install-from-pypi>.
""")
[2019-12-06 15:45:17,535] base_hook.py:84 INFO - Using connection to: id: sftp_default. Host: localhost, Port: 22, Schema: None, Login: airflow, Password: None, extra:

{'key_file': '~/.ssh/id_rsa', 'no_host_key_check': True}
[2019-12-06 15:45:17,539] base_hook.py:84 INFO - Using connection to: id: sftp_default. Host: localhost, Port: 22, Schema: None, Login: airflow, Password: None, extra:

{'key_file': '~/.ssh/id_rsa', 'no_host_key_check': True}
airflow@0030a4ae49df:~$ airflow list_dags
[2019-12-06 15:47:43,529] settings.py:252 INFO - settings.configure_orm(): Using pool settings. pool_size=5, max_overflow=10, pool_recycle=1800, pid=11223
/usr/local/lib/python3.7/site-packages/psycopg2/_init_.py:144: UserWarning: The psycopg2 wheel package will be renamed from release 2.8; in order to keep installing from binary please use "pip install psycopg2-binary" instead. For details see: <http://initd.org/psycopg/docs/install.html#binary-install-from-pypi>.
""")
[2019-12-06 15:47:44,631] _init_.py:51 INFO - Using executor LocalExecutor
[2019-12-06 15:47:44,631] dagbag.py:92 INFO - Filling up the DagBag from /usr/local/airflow/dags
[2019-12-06 15:47:48,998] base_hook.py:84 INFO - Using connection to: id: sftp_default. Host: localhost, Port: 22, Schema: None, Login: airflow, Password: None, extra:

{'key_file': '~/.ssh/id_rsa', 'no_host_key_check': True}
[2019-12-06 15:47:49,005] base_hook.py:84 INFO - Using connection to: id: sftp_default. Host: localhost, Port: 22, Schema: None, Login: airflow, Password: None, extra:

{'key_file': '~/.ssh/id_rsa', 'no_host_key_check': True}

This is on v1.10.6

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

[codecov-io]

Codecov Report

Merging #6748 into master will decrease coverage by 0.44%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #6748      +/-   ##
==========================================
- Coverage   84.81%   84.36%   -0.45%     
==========================================
  Files         669      669              
  Lines       37738    37740       +2     
==========================================
- Hits        32008    31841     -167     
- Misses       5730     5899     +169

Impacted Files	Coverage Δ
airflow/contrib/sensors/sftp_sensor.py	100% <100%> (ø)	⬆️
airflow/operators/mysql_operator.py	100% <0%> (ø)	⬆️
airflow/operators/mysql_to_hive.py	100% <0%> (ø)	⬆️
airflow/kubernetes/volume_mount.py	44.44% <0%> (-55.56%)	⬇️
airflow/kubernetes/volume.py	52.94% <0%> (-47.06%)	⬇️
airflow/kubernetes/pod_launcher.py	45.25% <0%> (-46.72%)	⬇️
airflow/executors/sequential_executor.py	56% <0%> (-32%)	⬇️
airflow/kubernetes/refresh_config.py	50.98% <0%> (-23.53%)	⬇️
...rflow/contrib/operators/kubernetes_pod_operator.py	78.2% <0%> (-20.52%)	⬇️
airflow/utils/sqlalchemy.py	89.83% <0%> (-6.78%)	⬇️
... and 8 more

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