v4.0.0 / 2022-03-27

Codename: The "barely a release" release

This version contains a single - sadly breaking - change.

• #251 Remove framework-specific
  route detection from collector middleware:
  In 3.0.0 we shipped a feature
  that attempted to use framework-specific information to determine the path of the
  request in Prometheus::Middleware::Collector.

  Sadly, we found out after shipping it that it was prone to multiple issues. We spent
  a decent amount of time looking into them in depth, and came to the conclusion that
  there wasn't any reasonable way to fix them - the issues are inherent to the feature.

  For a full, detailed write-up of our investigation, see this
  comment.

  Almost all users will be unaffected by this change, but it is breaking per the
  definition we've used for previous releases, so we've erred on the side of caution and
  bumped the major version to communicate that.

  If you use Sinatra or Grape with the Prometheus::Middleware::Collector, you will
  notice different path labels being generated. If not, this release will change
  nothing for you.

  If you want the behaviour from 3.0.0 - or any custom path label generation you'd
  prefer - we've updated our collector middleware
  documentation.

  This may be a breaking change. Labels may change in existing metrics.