Helper functions to write charms

The more charms we write, the more helper functions/methods we end up writing.

These are just a few examples:

• Function to generate passwords in the cassandra lib charm.
• Method to generate passwords in the mysql charm.
• Method to get the unit IP address

This code will end up being replicated across many charms and potentially in insecure ways.

Should something like ops.utils be the right place for all this kind of helper functions?

[benhoyt]

That said, even though I don’t think a lot of these functions will end up in ops itself, there’s nothing stopping you (or us) from making a separate opshelpers or similar library with a bunch of helper functions. It wouldn’t have to be so carefully vetted as ops core.

[benhoyt]

@Abuelodelanada Thanks for the suggestions. I’m not a big fan of adding generic tools like “generate password”. I don’t think we should be adding things that aren’t specific to charming to the operator framework. It’s fine to use your favourite password generation library from PyPI, or just write the one-liner generation function that satisfies your needs like you’ve done.

As far as fetching the unit’s IP address, doesn’t this depend on the network configuration and relations involved? Again, you can use the tools like get_binding() to do what your specific charm needs (like you’ve done). But I’d be happy to hear a more specific proposal for what you have in mind here, so we can discuss specifics.

@sed-i Can you provide a more specific explanation for what each of those functions is intended to do, perhaps with pseudo-code and a context example? Then we could discuss them on their specific merits. The only one I think we’d definitely not add is fetch_url – this is a minefield, and there are so many ways of fetching URL, so many options etc, that that’s definitely best left for a library like requests.