Add Metrics::Config which includes prepare hook.

bake.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2020-2024, by Samuel Williams.
+
+# Update the project documentation with the new version number.
+#
+# @parameter version [String] The new version number.
+def after_gem_release_version_increment(version)
+	context["releases:update"].call(version)
+	context["utopia:project:readme:update"].call
+end

lib/metrics.rb

@@ -6,3 +6,7 @@
 require_relative "metrics/version"
 require_relative "metrics/provider"
 require_relative "metrics/tags"
+
+# @namespace
+module Metrics
+end

lib/metrics/backend.rb

@@ -3,27 +3,11 @@
 # Released under the MIT License.
 # Copyright, 2021-2024, by Samuel Williams.
 
-require "console/event/failure"
+require_relative 'config'
 
 module Metrics
 	module Backend
-		# Require a specific trace backend.
-		def self.require_backend(env = ENV)
-			if backend = env["METRICS_BACKEND"]
-				begin
-					require(backend)
-				rescue LoadError => error
-					::Console::Event::Failure.for(error).emit(self, "Unable to load metrics backend!", backend: backend, severity: :warn)
-
-					return false
-				end
-
-				Metrics.extend(Backend::Interface)
-
-				return true
-			end
-		end
 	end
+
+	Config::DEFAULT.require_backend
 end
-
-Metrics::Backend.require_backend

lib/metrics/backend/capture.rb

@@ -3,7 +3,6 @@
 # Released under the MIT License.
 # Copyright, 2023-2024, by Samuel Williams.
 
-require "console"
 require_relative "../metric"
 
 module Metrics

lib/metrics/backend/console.rb

@@ -3,9 +3,10 @@
 # Released under the MIT License.
 # Copyright, 2021-2024, by Samuel Williams.
 
-require "console"
 require_relative "../metric"
 
+require "console"
+
 module Metrics
 	module Backend
 		module Console

lib/metrics/backend/test.rb

@@ -3,7 +3,6 @@
 # Released under the MIT License.
 # Copyright, 2021-2024, by Samuel Williams.
 
-require "console"
 require_relative "../metric"
 
 module Metrics

lib/metrics/config.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2024, by Samuel Williams.
+
+module Metrics
+	# Represents a configuration for the metrics library.
+	class Config
+		DEFAULT_PATH = ENV.fetch("METRICS_CONFIG_DEFAULT_PATH", "config/metrics.rb")
+
+		# Load the configuration from the given path.
+		# @parameter path [String] The path to the configuration file.
+		# @returns [Config] The loaded configuration.
+		def self.load(path)
+			config = self.new
+
+			if File.exist?(path)
+				config.instance_eval(File.read(path), path)
+			end
+
+			return config
+		end
+
+		# Load the default configuration.
+		# @returns [Config] The default configuration.
+		def self.default
+			@default ||= self.load(DEFAULT_PATH)
+		end
+
+		# Prepare the backend, e.g. by loading additional libraries or instrumentation.
+		def prepare
+		end
+
+		# Require a specific metrics backend implementation.
+		def require_backend(env = ENV)
+			if backend = env['METRICS_BACKEND']
+				begin
+					if require(backend)
+						Metrics.extend(Backend::Interface)
+
+						self.prepare
+
+						return true
+					end
+				rescue LoadError => error
+					warn "Unable to load metrics backend: #{backend.inspect}!"
+				end
+			end
+
+			return false
+		end
+
+		# Load the default configuration.
+		DEFAULT = self.default
+	end
+end

readme.md

@@ -19,6 +19,14 @@ Please see the [project documentation](https://socketry.github.io/metrics/) for
 
   - [Testing](https://socketry.github.io/metrics/guides/testing/index) - This guide explains how to write assertions in your test suite to validate `metrics` are being emitted correctly.
 
+## Releases
+
+Please see the [project releases](https://socketry.github.io/metrics/releases/index) for all releases.
+
+### Unreleased
+
+  - [Introduce `Metrics::Config` to Expose `prepare` Hook](https://socketry.github.io/metrics/releases/index#introduce-metrics::config-to-expose-prepare-hook)
+
 ## Contributing
 
 We welcome contributions to this project.

releases.md

@@ -0,0 +1,18 @@
+# Releases
+
+## Unreleased
+
+### Introduce `Metrics::Config` to Expose `prepare` Hook
+
+The `metrics` gem uses aspect-oriented programming to wrap existing methods to emit metrics. However, while there are some reasonable defaults for emitting metrics, it can be useful to customize the behavior and level of detail. To that end, the `metrics` gem now optionally loads a `config/metrics.rb` which includes a `prepare` hook that can be used to load additional providers.
+
+``` ruby
+# config/metrics.rb
+
+def prepare
+	require 'metrics/provider/async'
+	require 'metrics/provider/async/http'
+end
+```
+
+The `prepare` method is called immediately after the metrics backend is loaded. You can require any provider you want in this file, or even add your own custom providers.

test/metrics/backend.rb → test/metrics/config.rb

@@ -3,18 +3,20 @@
 # Released under the MIT License.
 # Copyright, 2024, by Samuel Williams.
 
-require "metrics/backend"
+require "metrics/config"
 require "json"
 
 require "sus/fixtures/console"
 
-describe Metrics::Backend do
+describe Metrics::Config do
+	let(:config) {subject.default}
+
 	with ".require_backend" do
 		include_context Sus::Fixtures::Console::CapturedLogger
 
 		it "logs a warning if backend cannot be loaded" do
 			expect(
-				subject.require_backend({"METRICS_BACKEND" => "metrics/backend/missing"})
+				config.require_backend({"METRICS_BACKEND" => "metrics/backend/missing"})
 			).to be == false
 
 			expect_console.to have_logged(