Initial commit: declare and collect web request metrics

.gitignore

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+/.bundle/
+/.yardoc
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/
+Gemfile.lock
+
+# rspec failure tracking
+.rspec_status

.rspec

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+--format documentation
+--color
+--require spec_helper

.rubocop.yml

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+---
+require:
+- rubocop-rspec
+
+AllCops:
+  TargetRubyVersion: 2.3
+
+Metrics/BlockLength:
+  Exclude:
+  - "Gemfile"
+  - "spec/**/*"
+
+Style/BracesAroundHashParameters:
+  EnforcedStyle: context_dependent
+
+Style/StringLiterals:
+  EnforcedStyle: double_quotes
+
+# Allow to use let!
+RSpec/LetSetup:
+  Enabled: false
+
+RSpec/MultipleExpectations:
+  Enabled: false
+
+Bundler/OrderedGems:
+  Enabled: false
+
+Style/TrailingCommaInArguments:
+  Description: 'Checks for trailing comma in argument lists.'
+  StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#no-trailing-params-comma'
+  Enabled: true
+  EnforcedStyleForMultiline: consistent_comma
+
+Style/TrailingCommaInArrayLiteral:
+  Description: 'Checks for trailing comma in array literals.'
+  StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#no-trailing-array-commas'
+  Enabled: true
+  EnforcedStyleForMultiline: consistent_comma
+
+Style/TrailingCommaInHashLiteral:
+  Description: 'Checks for trailing comma in hash literals.'
+  StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#no-trailing-array-commas'
+  Enabled: true
+  EnforcedStyleForMultiline: consistent_comma
+

.travis.yml

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+sudo: false
+language: ruby
+rvm:
+  - 2.5.1
+before_install: gem install bundler -v 1.16.1

Gemfile

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+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
+
+# Specify your gem's dependencies in evil-metrics-rails.gemspec
+gemspec
+
+group :development, :test do
+  gem "pry"
+  gem "pry-byebug", platform: :mri
+
+  gem "rubocop"
+  gem "rubocop-rspec"
+end

LICENSE.txt

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+The MIT License (MIT)
+
+Copyright (c) 2018 Andrey Novikov
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# Evil::Metrics::[Rails]
+
+Built-in metrics for out-of-the box [Rails] applications monitoring 
+
+if your monitoring system already collects Rails metrics (e.g. NewRelic) then you don't need this gem.
+
+## Installation
+
+Add this line to your application's Gemfile:
+
+```ruby
+gem 'evil-metrics-rails'
+# Then add monitoring system adapter, e.g.:
+# gem 'evil-metrics-prometheus'
+```
+
+And then execute:
+
+    $ bundle
+
+## Metrics
+
+ - Total web requests received: `rails_requests_total`
+ - Web request duration: `rails_request_duration` (in seconds)
+ - Views rendering duration: `rails_view_runtime` (in seconds)
+ - DB request duration: `rails_db_runtime` (in seconds)
+
+
+## Hooks
+
+ - `on_controller_action`: Allows to collect
+
+    ```ruby
+    Evil::Metrics::Rails.on_controller_action do |event, labels|
+      next unless event.payload[:ext_service_runtime]
+      time_in_seconds = event.payload[:ext_service_runtime] / 1000.0
+      rails_ext_service_runtime.measure(labels, time_in_seconds)
+    end
+    ```
+
+## Development
+
+After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
+
+To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
+
+## Contributing
+
+Bug reports and pull requests are welcome on GitHub at https://github.com/evil-metrics/evil-metrics-rails.
+
+## License
+
+The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).
+
+[Rails]: https://rubyonrails.org "Ruby on Rails MVC web-application framework optimized for programmer happiness"

Rakefile

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+# frozen_string_literal: true
+
+require "bundler/gem_tasks"
+require "rspec/core/rake_task"
+
+RSpec::Core::RakeTask.new(:spec)
+
+task default: :spec

bin/console

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+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "bundler/setup"
+require "evil/metrics/rails"
+
+# You can add fixtures and/or initialization code here to make experimenting
+# with your gem easier. You can also use a different console, if you like.
+
+require "pry"
+Pry.start

bin/setup

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+#!/usr/bin/env bash
+set -euo pipefail
+IFS=$'\n\t'
+set -vx
+
+bundle install
+
+# Do any other automated setup that you need to do here

evil-metrics-rails.gemspec

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+# frozen_string_literal: true
+
+Gem::Specification.new do |spec|
+  spec.name          = "evil-metrics-rails"
+  spec.version       = "0.1.0"
+  spec.authors       = ["Andrey Novikov"]
+  spec.email         = ["[email protected]"]
+
+  spec.summary       = "Extensible metrics for monitoring Ruby on Rails application"
+  spec.description   = "Easy collecting your Rails apps metrics"
+  spec.homepage      = "https://github.com/evil-metrics/evil-metrics-rails"
+  spec.license       = "MIT"
+
+  spec.files         = `git ls-files -z`.split("\x0").reject do |f|
+    f.match(%r{^(test|spec|features)/})
+  end
+  spec.bindir        = "exe"
+  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.require_paths = ["lib"]
+
+  spec.add_dependency "evil-metrics"
+  spec.add_dependency "rails"
+
+  spec.add_development_dependency "bundler", "~> 1.16"
+  spec.add_development_dependency "rake", "~> 10.0"
+  spec.add_development_dependency "rspec", "~> 3.0"
+end

lib/evil/metrics/rails.rb

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+# frozen_string_literal: true
+
+require "evil/metrics"
+require "evil/metrics/rails/railtie"
+
+module Evil
+  module Metrics
+    module Rails
+      LONG_RUNNING_REQUEST_BUCKETS = [
+        0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10, # standard
+        30, 60, 120, 300, 600, # Sometimes requests may be really long-running
+      ].freeze
+
+      class << self
+        def controller_handlers
+          @controller_handlers ||= []
+        end
+
+        def on_controller_action(&block)
+          controller_handlers << block
+        end
+
+        def install!
+          Evil::Metrics.configure do
+            group :rails
+
+            counter   :requests_total, comment: "A counter of the total number of HTTP requests rails processed."
+            histogram :request_duration, unit: :seconds, buckets: LONG_RUNNING_REQUEST_BUCKETS,
+                                         comment: "A histogram of the response latency."
+            histogram :view_runtime, unit: :seconds, buckets: LONG_RUNNING_REQUEST_BUCKETS,
+                                     comment: "A histogram of the view rendering time."
+            histogram :db_runtime, unit: :seconds, buckets: LONG_RUNNING_REQUEST_BUCKETS,
+                                   comment: "A histogram of the activerecord execution time."
+
+            ActiveSupport::Notifications.subscribe "process_action.action_controller" do |*args|
+              event = ActiveSupport::Notifications::Event.new(*args)
+              labels = {
+                controller: event.payload[:params]["controller"],
+                action: event.payload[:params]["action"],
+                status: event.payload[:status],
+                format: event.payload[:format],
+                method: event.payload[:method].downcase,
+              }
+
+              rails_requests_total.increment(labels)
+              rails_request_duration.measure(labels, Evil::Metrics::Rails.ms2s(event.duration))
+              rails_view_runtime.measure(labels, Evil::Metrics::Rails.ms2s(event.payload[:view_runtime]))
+              rails_db_runtime.measure(labels, Evil::Metrics::Rails.ms2s(event.payload[:db_runtime]))
+
+              Evil::Metrics::Rails.controller_handlers.each do |handler|
+                handler.call(event, labels)
+              end
+            end
+          end
+        end
+
+        def ms2s(ms)
+          (ms.to_f / 1000).round(3)
+        end
+      end
+    end
+  end
+end

lib/evil/metrics/rails/railtie.rb

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+# frozen_string_literal: true
+
+module Evil
+  module Metrics
+    module Rails
+      class Railtie < ::Rails::Railtie # :nodoc:
+        config.after_initialize do
+          next unless ::Rails.const_defined?(:Server)
+
+          ::Evil::Metrics::Rails.install!
+        end
+      end
+    end
+  end
+end

spec/evil/prome/rails_spec.rb

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+# frozen_string_literal: true
+
+RSpec.describe Evil::Metrics::Rails do
+  it "has a version number" do
+    expect(Evil::Metrics::Rails::VERSION).not_to be nil
+  end
+
+  it "does something useful" do
+    expect(false).to eq(true)
+  end
+end

spec/spec_helper.rb

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+# frozen_string_literal: true
+
+require "bundler/setup"
+require "evil/metrics/rails"
+
+RSpec.configure do |config|
+  # Enable flags like --only-failures and --next-failure
+  config.example_status_persistence_file_path = ".rspec_status"
+
+  # Disable RSpec exposing methods globally on `Module` and `main`
+  config.disable_monkey_patching!
+
+  config.expect_with :rspec do |c|
+    c.syntax = :expect
+  end
+end