Upgrade to using hashicorp/[email protected]

[mkeeler]

Description

On the surface this is a fairly mechanical change in deps and imports. Instead of consuming armon/go-metrics, Nomad will now use the latest version of hashicorp/go-metrics. Previous attempts to upgrade resulted in missing metrics and were reverted. This time is different because all libraries within the hashicorp namespace have been instrumented to use a special compat package within hashicorp/go-metrics to allow for a compile time build tag to control the metrics module used by all libraries.

This PR does 3 things:

• Updates dependencies of the relevant libraries (memberlist, serf, raft, raft-boltdb) to ensure they can support the build tag.
• Changes all imports of armon/go-metrics to hashicorp/go-metrics
• Modifies the GO_TAGS variable handling within the makefile to use the hashicorpmetrics build tag (global library opt-in to metrics emission via the hashicorp/go-metrics module)

Testing & Reproduction steps

• make dev
• mkdir data
• nomad agent -server -data-dir $(pwd)/data
• curl localhost:4646/v1/metrics

Now ensure that metrics from all the libraries are still seen. I checked that there was at least one from serf, memberlist, raft and raft-boltdb.

Contributor Checklist

• Changelog Entry If this PR changes user-facing behavior, please generate and add a
  • No user facing behavioral changes.
    changelog entry using the make cl command.
• Testing Please add tests to cover any new functionality or to demonstrate bug fixes and ensure regressions will be caught.
  • No functional changes to test.
• Documentation If the change impacts user-facing functionality such as the CLI, API, UI,
  and job configuration, please update the Nomad website documentation to reflect this. Refer to
  the website README for docs guidelines. Please also consider whether the
  change requires notes within the upgrade guide.
  • No user facing changes to document.

Reviewer Checklist

• Backport Labels Please add the correct backport labels as described by the internal
  backporting document.
• Commit Type Ensure the correct merge method is selected which should be "squash and merge"
  in the majority of situations. The main exceptions are long-lived feature branches or merges where
  history should be preserved.
• Enterprise PRs If this is an enterprise only PR, please add any required changelog entry
  within the public repository.

[schmichael]

LGTM, just want to check a couple points before approving.

[schmichael]

Just noting that our reason for pinning a specific version of armon/go-metrics appears to have been resolved years ago: hashicorp/go-metrics#146

So dropping this pinning is not only ok, but a great side effect.

[mkeeler]

@schmichael I think this is ready for a final look. I migrated the Nomad root module to utilizing the compat package to ensure all those importing that module can control which metric module is used.

[mkeeler]

Also while Consul's API package has a memberlist/serf dependency, I have not updated that module in this PR because the equivalent Consul PRs haven't landed yet. This should be perfectly fine because Consul's API package doesn't emit metrics and only uses those dependencies for Coordinate structures types (which Nomad doesn't consume anyways).

[schmichael]

LGTM! Thanks so much for taking this on @mkeeler !