Introduce hashicorp/go-metrics compatibility

[mkeeler]

This PR migrates the library to using github.com/hashicorp/go-metrics/compat instead of github.com/armon/go-metrics.

Applications consuming the library can control whether metrics get emitted to either armon/go-metrics or hashicorp/go-metrics by specifying either the armonmetrics or hashicorpmetrics build tags. The default behavior is currently to prefer armon/go-metrics for maximum backwards compatibility.

Future PRs will:

• Bump the hashicorp/go-metrics and hashicorp/memberlist versions to one where the default behavior is to emit metrics using hashicorp/go-metrics (Timeline: mid-2025)
• Remove compat package usage with direct usage of hashicorp/go-metrics (Timeline: end-2025)

TODO:

• Pull in a tagged version of hashicorp/go-metrics once upstream PR is merged
• Pull in a tagged version of hashicorp/memberlist once upstreamPR is merged

[mukeshjc]

LGTM

[RSWilli]

How is it that armon/go-metrics is only deprecated, when you can't even install it from a fresh go mod cache? If you click on the URL: https://github.com/armon/go-metrics then you're redirected to https://github.com/hashicorp/go-metrics, which the go compiler doesn't like.

[mkeeler]

Maybe I should clarify the wording in the readme.

This library (and all others within the hashicorp namespace) emitting metrics to the armon/go-metrics global handler is deprecated. Right now the compatibility shim in place allows metrics to flow to either of the modules but that isn't a state we want to maintain indefinitely. Mid 2025 my plan is to flip the default behavior to prefer emitting metrics towards hashicorp/go-metrics (build tags can still opt-out). Then at the end of the year my plan is to remove the compatibility layer all together and only emit metrics to hashicorp/go-metrics.

As for using armon/go-metrics, you can still go get github.com/armon/[email protected]. When Go finds this tag, the module declared in the downloaded go.mod will be armon/go-metrics and the compiler wont complain. Using, latest or any of the later versions is broken due to the module renaming.