Add healthcheck endpoint for web (mastodon#11770)

Gemfile

@@ -50,6 +50,7 @@ gem 'fastimage'
 gem 'goldfinger', '~> 2.1'
 gem 'hiredis', '~> 0.6'
 gem 'redis-namespace', '~> 1.5'
+gem 'health_check', '~> 3.0'
 gem 'htmlentities', '~> 4.3'
 gem 'http', '~> 3.3'
 gem 'http_accept_language', '~> 2.1'

Gemfile.lock

@@ -278,6 +278,8 @@ GEM
  concurrent-ruby (~> 1.0)
  hashdiff (1.0.0)
  hashie (3.6.0)
+ health_check (3.0.0)
+ railties (>= 5.0)
  heapy (0.1.4)
  highline (2.0.1)
  hiredis (0.6.3)
@@ -706,6 +708,7 @@ DEPENDENCIES
  fuubar (~> 2.4)
  goldfinger (~> 2.1)
  hamlit-rails (~> 0.2)
+ health_check (~> 3.0)
  hiredis (~> 0.6)
  htmlentities (~> 4.3)
  http (~> 3.3)

app/controllers/application_controller.rb

@@ -41,7 +41,7 @@ def raise_not_found
  private
 
  def https_enabled?
- Rails.env.production?
+ Rails.env.production? && !request.path.start_with?('/health')
  end
 
  def authorized_fetch_mode?

config/initializers/health_check.rb

@@ -0,0 +1,6 @@
+HealthCheck.setup do |config|
+ config.uri = 'health'
+
+ config.standard_checks = %w(database migrations cache)
+ config.full_checks = %w(database migrations cache)
+end

config/routes.rb

@@ -10,6 +10,8 @@
 
  mount LetterOpenerWeb::Engine, at: 'letter_opener' if Rails.env.development?
 
+ health_check_routes
+
  authenticate :user, lambda { |u| u.admin? } do
  mount Sidekiq::Web, at: 'sidekiq', as: :sidekiq
  mount PgHero::Engine, at: 'pghero', as: :pghero

docker-compose.yml

@@ -43,7 +43,7 @@ services:
  - external_network
  - internal_network
  healthcheck:
- test: ["CMD-SHELL", "wget -q --spider --header 'x-forwarded-proto: https' --proxy=off localhost:3000/api/v1/instance || exit 1"]
+ test: ["CMD-SHELL", "wget -q --spider --proxy=off localhost:3000/health || exit 1"]
  ports:
  - "127.0.0.1:3000:3000"
  depends_on:
@@ -63,7 +63,7 @@ services:
  - external_network
  - internal_network
  healthcheck:
- test: ["CMD-SHELL", "wget -q --spider --header 'x-forwarded-proto: https' --proxy=off localhost:4000/api/v1/streaming/health || exit 1"]
+ test: ["CMD-SHELL", "wget -q --spider --proxy=off localhost:4000/api/v1/streaming/health || exit 1"]
  ports:
  - "127.0.0.1:4000:4000"
  depends_on: