Should there a be a helper that checks the status of snap/pebble services?

[sinapah]

In some integration tests, charm authors find themselves writing helpers to fetch and assert on the status of snap services. An example would be https://github.com/canonical/opentelemetry-collector-operator/blob/9fa23d2d2dcd14e21966c3f3b784492cc9ae969d/tests/integration/helpers.py#L49-L60

I wonder if it makes sense to add two helper methods for checking the status of a snap or pebble service.

The first helper would have a signature roughly like this:

def check_snap_status(                                                                                                                                                          
         self,                                                                                                                                                                       
         app: str,                                                                                                                                                                   
         snap: str,                                                                                                                                                                  
         unit_num: int = 0,                                                                                                                                                          
     ) -> str:

Its usage would be something like:

import jubilant
...
assert jubilant.check_snap_status("otelcol", "opentelemetry-collector", 1) == "active"

Along the same lines, the second helper would have a signature roughly like this:

def check_snap_status(                                                                                                                                                          
         self,                                                                                                                                                                       
         app: str,                                                                                                                                                                   
         pebble_service: str,                                                                                                                                                                  
         unit_num: int = 0,
         containre_name: str,                                                                                                                                                          
     ) -> str:

Its usage would be something like:

import jubilant
...
assert jubilant.check_snap_status("otelcol", "otelcol", 1, "otelcol") == "active"

I'd be happy to contribute this if you think it'd make a valuable addition. My question is, since _juju.py is merely a wrapper around the Juju CLI, where should a helper like this go? In a dedicated _helpers.py file or should it be added to the existing _test_helpers.py file?

[tonyandrewmeyer]

Hi @sinapah ! Thanks for this suggestion, and offering to contribute it. I think we're very unlikely to add this to Jubilant itself. We've resisted adding helpers that go beyond wrapping the Juju CLI (other than temp_model, and I think that would even be unlikely to make it if the decision was made today).

However, Charm Tech gets requests for common helpers like this reasonably frequently, and we're pretty keen to solve that problem. We had a chat about this today, and feel they should be (a) in pytest-jubilant, especially ones like this that sit on top of Jubilant, or (b) in a new pytest-charming that Charm Tech would maintain, which could hold a broader range like getting resources as well, or (c) a set of small pytest-x packages, like pytest-pebble. We might be able to fit one of these in as a blue roadmap item this cycle, especially if there are contributions as you offered, or we might be able to make it a 27.04 item.

A bunch of the team are away at the moment, so confirming we want to go ahead, and deciding where the helpers should live and when we can do it will need to wait for a few weeks. We'll get back to you asap.

[sinapah]

Thanks for the explanation @tonyandrewmeyer! All the suggestions sound great to me. Whenever the team is ready to go ahead with any of these ideas, I'd be happy to offer my help 😊

[tromai]

Charm Tech are happy to add this in pytest-jubilant. Likely using juju exec and parse the snap/pebble output.

Something to consider to avoid parsing text output, and have an API instead:

• juju exec curl ? (curl might not always available)
• juju exec python -c "import urllib; ..."?

[james-garner-canonical]

Update based on further discussion: we're happy to consider this for pytest-jubilant, but aren't committed to adding it yet. What would help us decide is knowing how many charms are (or should) be using helpers like this. For example, if this is needed by only a handful of charms, then it seems reasonable for those charms to just define their own helpers.