[MISC] Rework helpers to avoid connections from test host

[astrojuanlu]

Issue

Make execute_queries_on_unit and is_connection_possible independent from MicroK8s routes.

This makes it easier to run the test suite against HA Canonical K8s, which is closer to how production setups actually are.

Solution

Checklist

• I have added or updated any relevant documentation.
• I have cleaned any remaining cloud resources from my accounts.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 4 comments.

[paulomach]

We should also be able to get rid of mysql-connector-python dependency in integration group of pyproject.toml.

And I am happy to merge this to unblock #341 but we should try to use the same approach on the machine tests also.

[astrojuanlu]

After discussing with @paulomach , we realized that we actually don't need this for #341. Canonical K8s will allow external connections, just not in HA mode.

At the same time, I ran into some challenges with this PR, in particular with test_saturate_max_connections.py. So I'm leaving this in draft until we have time to go back to it.

[astrojuanlu]

Actually, on second thought, leaving that test aside, this was ready for review and most tests were passing.

[astrojuanlu]

(This means that we can't remove the mysql-connector-python dependency yet, but we are much closer)

[astrojuanlu]

Rebased. LMK @paulomach if you still think it's worth moving forward with this.

[paulomach]

Rebased. LMK @paulomach if you still think it's worth moving forward with this.

Yes, but not right now. We can keep it dormant for now and get back after current pulse(TM)

[sinclert-canonical]

👋🏻 Hey folks! I remember seeing this PR and being confused. A few questions to start:

• What is the context around this PR?
• Are we migrating our MySQL 8.4 test suite to HA Canonical K8s?
• Why do we need to issue SET ROLE ALL queries explicitly?

[paulomach]

👋🏻 Hey folks! I remember seeing this PR and being confused. A few questions to start:

* What is the context around this PR?

I've sent @astrojuanlu on a wrong path about canonical k8s, as I initially thought that ck8s was not routing local external traffic to pods. It does. I saw this issue while running repo tests against a ck8s HA setup (not a local snap). So the idea boils down to ditch usage of local mysql-connector-python to run queries on pods/units, and use a juju.ssh leveraging the mysqlsh cli always present on the units to execute queries, allowing us to (1) drop mysql-connector-python requirement and (2) exactly same method for the substrates, as side-effects

* Are we migrating our MySQL 8.4 test suite to HA Canonical K8s?

No, that will make runners cry.

* Why do we need to issue `SET ROLE ALL` queries explicitly?

Don't know.

[astrojuanlu]

Why do we need to issue SET ROLE ALL queries explicitly?

Turns out MySQL Shell does not respect activate_all_roles_on_login = ON when using the X protocol, which is the default for SQL and Python modes. This affects all the tests that use extra roles.

This might be a fundamental feature of how the X protocol works, but I haven't been able to pinpoint that in the official documentation.