feat(registry): add with_prefix_and_labels constructor

[popadi]

Added new constructor per discussion in #146.

[mxinden]

Put simply there are two ways to create a registry:

1. From scratch e.g. via Registry::with_prefix or <Registry as Default>::default.
2. From a parent registry e.g. via Registry::sub_registry_with_prefix.

What do you think of changing this patch to follow (2) and not (1). It would be a convenience method for folks wanting a sub registry with a prefix and one or more labels. It would still be possible for folks that want (1) via Registry::default().sub_registry_with_prefix_and_labels(..).

[popadi]

What do you think of changing this patch to follow (2) and not (1). It would be a convenience method for folks wanting a sub registry with a prefix and one or more labels.

Is there any reason there is a separate Registry::with_prefix if Registry::sub_registry_with_prefix already exist then? The root registry with default labels might be not used that much, but it's definitely a usecase people might have.

It would still be possible for folks that want (1) via Registry::default().sub_registry_with_prefix_and_labels(..).

I think we might still want something similar to (1), at least that's my usecase (and that's why I made this pull request in the first place). If I really want ALL my metrics to have a prefix AND a bunch of labels, it seems a bit weird to simulate the root registry using a sub-registry.

[popadi]

@mxinden any update/feedback on this?

[mxinden]

Sorry for the delay here. Thank you for expanding on your use-case. Agreed that we should support it.

For the sake of consistency, what do you think about also adding Registry::with_labels?

Also can you bump the crate version in Cargo.toml to v0.21.2 and add a changelog entry in CHANGELOG.md?

[popadi]

Sorry for the delay here. Thank you for expanding on your use-case. Agreed that we should support it.

For the sake of consistency, what do you think about also adding Registry::with_labels?

Also can you bump the crate version in Cargo.toml to v0.21.2 and add a changelog entry in CHANGELOG.md?

Done, added the extra method + updated changelog and bumped version.
Thanks for the feedback

[mxinden]

Thank you for the continued work!

[mxinden]

Published and tagged prometheus-client v0.21.2.