v3.0.0 / 2022-02-05

This new major version includes some breaking changes. They should be reasonably easy to
adapt to, but please read the details below:

Breaking changes

Please refer to UPGRADING.md for details on upgrading from versions
< 3.0.0.

• #206 Include SCRIPT_NAME when
  determining path in Collector:
  When determining the path for a request, Rack::Request prefixes the
  SCRIPT_NAME. This was a problem with our code when using mountable engines,
  where the engine part of the path gets lost. This patch fixes that to include SCRIPT_NAME as part of the path.

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

• #245 Use framework-specific route
  info and handle consecutive path segments containing IDs in Collector:
  When generating the path label, we now use framework-specific information from the
  request environment to produce better labels for apps written in the Sinatra and Grape
  frameworks. Rails doesn't provide the information we need to do the same there, but we
  hope to get such functionality added in a future release.

  Our framework-agnostic fallback (which Rails apps will use) has also been improved. It
  now supports stripping IDs/UUIDs from consecutive path segments, where previously only
  alternating segments would be correctly stripped.

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

• #209 Automatically initialize metrics
  without labels.
  Following the Prometheus Best Practices,
  client libraries are expected to automatically export a 0 value when declaring a metric
  that has no labels.
  We missed this recommendation in the past, and this wasn't happening. Starting from this
  version, all metrics without labels will be immediately exported with 0 value, without
  need for an increment / observation.

  This may be a breaking change. Depending on your particular metrics, this may
  result in a significant increase to the number of time series being exported. We
  recommend you test this and make sure it doesn't cause problems.

• #220 and #234
  Improvements to Pushgateway client:

  • The job parameter is now mandatory when instantiating Prometheus::Client::Push
    and will raise ArgumentError if not specified, or if nil or an empty string/object
    are passed.
  • The Prometheus::Client::Push initializer now takes keyword arguments.
  • You can now pass a set of arbitrary key-value pairs (grouping_key) to uniquely
    identify a job instance, rather than just an instance label.
  • Fixed URI escaping of spaces in the path when pushing to to Pushgateway. In the
    past, spaces were being encoded as + instead of %20, which resulted in
    incorrect label values in the grouping key.
  • We now correctly encode special values in job and grouping_key that can't
    ordinarily be represented in the URL. This mean you can have a forward slash (/)
    in a grouping key label value, or set one to the empty string.
  • We validate that labels in your grouping_key don't clash with labels in the
    metrics being submitted, and raise an error if they do.
  • We raise an error on a non-2xx HTTP response from the Pushgateway.

  This is a breaking change if you use Pushgateway. You will need to update your
  code to pass keyword arguments to the Prometheus::Client::Push initializer.

• #242 Move HTTP Basic
  Authentication credentials in Prometheus::Client::Push to separate method call:
  In earlier versions, these were provided as part of the gateway URL, which had some
  significant downsides when it came to special characters in usernames/passwords.

  These credentials must now be passed via an explicit call to basic_auth on an
  instance of Prometheus::Client::Push.

  This is a breaking change if you use Pushgateway with HTTP Basic Authentication.
  You will need to update your code to call this method instead of including the
  credentials in the URL.

• #236 Validate label names:
  Previously, we didn't validate that label names match the character set required by
  Prometheus ([a-zA-Z_][a-zA-Z0-9_]*). As of this release, we raise an error if a
  metric is initialized with label names that don't match that regex.

  This is a breaking change. While it's likely that Prometheus server would have
  been failing to scrape metrics with such labels anyway, declaring them will now cause
  an error to be raised in your code.

• #237 Drop support for old Ruby versions:
  Ruby versions below 2.6 are no longer supported upstream, and client_ruby is no
  longer tested against them.

  This may be a breaking change. We no longer make efforts to ensure that
  client_ruby works on older versions, and any issues filed specific to them will be
  considered invalid.

New Features

• #199 Add port filtering option
  to Exporter middleware.
  You can now specify a port when adding Prometheus::Middleware::Exporter to your
  middleware chain, and metrics will only be exported if the /metrics request comes
  through that port.

• #222 Enable configuring Net::HTTP
  timeouts for Pushgateway calls.
  You can now specify open_timeout and read_timeout when instantiating
  Prometheus::Client::Push, to control these timeouts.

Code improvements and bug fixes

• #201 Make all registry methods
  thread safe.

• #227 Fix with_labels bug that
  made it completely non-functional, and occasionally resulted in DirectFileStore file
  corruption.