[AIRFLOW-3268] Cannot pass SSL dictionary to mysql connection via URL

[potiuk]

Make sure you have checked all steps below.

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-3268

Description

• Here are some details about my PR, including screenshots of any UI changes:
  It is impossible to pass 'ssl' dictionary to MySql hook as an extrai
  param via URL connection. While there is a code to pass the 'ssl'
  extra query parameter, MySqldb requires this parameter to be
  dictionary. When you want to create a connection via URL,
  you can at most have ?ssl= url-encoded string rather than
  dictionary and this is how it is passed (as string). What happens
  then in MySqldb, is that all SSL parameters are ignored
  and MySQL establishes a non-SSL connection silently.

This is fixed by detecting if 'ssl' is a string and converting
it to json dictionary in such case.

Tests

• My PR adds the following unit tests
  TestMySqlHookConn:
  test_get_conn_ssl_as_dictionary
  test_get_conn_ssl_as_string

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.
  No new functionality

Code Quality

• Passes flake8

[codecov-io]

Codecov Report

Merging #4113 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4113      +/-   ##
==========================================
+ Coverage   76.69%   76.71%   +0.01%     
==========================================
  Files         199      199              
  Lines       16233    16238       +5     
==========================================
+ Hits        12450    12457       +7     
+ Misses       3783     3781       -2

Impacted Files	Coverage Δ
airflow/hooks/mysql_hook.py	92.98% <100%> (+2.59%)	⬆️
airflow/models.py	92.15% <0%> (+0.04%)	⬆️

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[kaxil]

Can this be documented somewhere i.e. what can be passed into Extras field?

Currently, a user needs to check the source code to see what can be passed which isn't ideal.

[potiuk]

Hey @kaxil - Why not :). I added it now, reverse engineering it from the code. It's good to leave the world a bit better than you found. I added useful documentation now to MySQL connection. I will soon submit CloudSQL query one which I will add similar info about new cloudsql:// connection and about underlying Postgres connection as well.

[kaxil]

@potiuk Thanks, appreciate that :) . Can you update the commit message as well to something along the line of "Fix Issue with Extras field in MySQL connection" or something that help users identify what issue was solved.

The current commit message is more of a "Jira issue".

[potiuk]

Sure :). Done.

[kaxil]

Awesome. Thanks @potiuk