Support Various Prometheus Client Versions

[kojiromike]

closes #128
closes #127

also see #125
also see #126

[coveralls]

Coverage decreased (-0.2%) to 84.718% when pulling 943731c on kojiromike:choose-your-own-adventure into 02b2ea3 on rycus86:master.

[rycus86]

Legend, thanks a lot! I'll bump the version (and restore older Python version support perhaps) and tag it for release.

[kojiromike]

@rycus86 do you have a way I can add both versions of the client to the test matrix?

[rycus86]

Do you mean test with both versions of prometheus_client? I could imagine adding some pinning to the requirements.txt file before starting unit/integration tests, but I don't think it's necessary to be honest.

[kojiromike]

Do you mean test with both versions of prometheus_client?

Right, it looks like you have a build matrix in Actions for testing different Python versions. I was just suggesting we could add a matrix for testing multiple versions of other dependencies, if you want.

[rycus86]

we could add a matrix for testing multiple versions of other dependencies

Yes, we could but I don't think it's necessary (do you know other packages that do similar things?), but can reconsider later if this becomes a regular problem.

PS: love the branch name 👍

[csmarchbanks]

I just wanted to chime in here, sorry about the hassle! The rename was not meant as a breaking change, and I plan to revert back to the old name in prometheus/client_python#796. It looks like with your fix will be fine. If you see breaking changes in prometheus_client in the future feel free to open an issue and I will try to resolve it as quickly as I can!

[Starkteetje]

Note that reverting the name change is a breaking change again for everyone pinning prometheus-flask-exporter 0.20 and not pinning prometheus-client at the same time.

[rycus86]

Which is resolved in 0.20.1 :/

[Starkteetje]

Maybe I'm misunderstanding you, but 0.20.1 still doesn't seem to pin the prometheus-client version either in https://github.com/rycus86/prometheus_flask_exporter/blob/0.20.1/requirements.txt or https://github.com/rycus86/prometheus_flask_exporter/blob/0.20.1/setup.py

Compare i.e. with https://github.com/pallets/flask/blob/main/setup.py where the accepted versions are declared

Running pip install prometheus-flask-exporter this leads to Requirement already satisfied: prometheus-client in ./lib/python3.8/site-packages (from prometheus-flask-exporter) (0.14.0) but Requirement already satisfied: Jinja2>=3.0 in ./lib/python3.8/site-packages (from flask->prometheus-flask-exporter) (3.1.1). So for prometheus-client any version is pulled, but for Jinja2 it needs to be >=3 due to the requirement in Flask's setup.py

Though to be fair >= wouldn't have prevented the incompatibility in this case as the breaking change was introduced without increasing the major version

[kojiromike]

@Starkteetje the fix in 0.20.1 does not require pinning. It is designed to work with either version-range of prometheus-client. If prometheus-client reverts the incompatibility, then 0.20.1 should still work.

[Starkteetje]

I see. That makes sense, especially in light of the change maybe being reverted.
However, the root cause is not tackled by this. A breaking change in Flask (less of an issue as its probably a direct dependency of whoever is using prometheus_flask_exporter) or a breaking change in prometheus-client are both likely to break existing setups. Pinning the version with ~= would mitigate this if both dependencies adhere to semver (and prometheus-client had major version 1), so I'd still see value in that.
Pinning with == would resolve the issue completely, but that might be too strong of a dependency 🤷‍♂️

[rycus86]

I don't think I want to start adding requirements on versions of dependencies here, I don't want this library to prescribe what versions it can work with. As long as we can reasonably make it work with different/multiple versions, we should be OK?

[rycus86]

I just wanted to chime in here, sorry about the hassle! The rename was not meant as a breaking change, and I plan to revert back to the old name in prometheus/client_python#796. It looks like with your fix will be fine. If you see breaking changes in prometheus_client in the future feel free to open an issue and I will try to resolve it as quickly as I can!

No worries, and thanks for looking into it! ❤️ I didn't even realize this library is on your radar. 😄