Add capistrano task to remove application from the load balancer. (#74)

* Add capistrano task to remove application from the load balancer.

Closes #73

Gemfile

@@ -3,7 +3,7 @@
 source 'https://rubygems.org'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-gem 'health-monitor-rails'
+gem 'health-monitor-rails', '12.4.0'
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 7.1.0'

Gemfile.lock

@@ -129,7 +129,7 @@ GEM
     ffi (1.17.0-x86_64-linux-gnu)
     globalid (1.2.1)
       activesupport (>= 6.1)
-    health-monitor-rails (12.3.0)
+    health-monitor-rails (12.4.0)
       railties (>= 6.1)
     i18n (1.14.6)
       concurrent-ruby (~> 1.0)
@@ -339,7 +339,7 @@ DEPENDENCIES
   capistrano-rails
   capybara
   coffee-rails (~> 4.2)
-  health-monitor-rails
+  health-monitor-rails (= 12.4.0)
   jbuilder
   listen
   pagy (~> 3.5)

config/deploy.rb

@@ -12,6 +12,38 @@
 # Default deploy_to directory is /var/www/my_app_name
 set :deploy_to, '/opt/geaccirc'
 
+namespace :application do
+  # You can/ should apply this command to a single host
+  # cap --hosts=geaccirc-staging2.princeton.edu staging application:remove_from_nginx
+  desc 'Marks the server(s) to be removed from the loadbalancer'
+  task :remove_from_nginx do
+    count = 0
+    on roles(:app) do
+      count += 1
+    end
+    if count > (roles(:app).length / 2)
+      raise 'You must run this command on no more than half the servers utilizing the --hosts= switch'
+    end
+
+    on roles(:app) do
+      within release_path do
+        execute :touch, 'public/remove-from-nginx'
+      end
+    end
+  end
+
+  # You can/ should apply this command to a single host
+  # cap --hosts=geaccirc-staging2.princeton.edu staging application:serve_from_nginx
+  desc 'Marks the server(s) to be added back to the loadbalancer'
+  task :serve_from_nginx do
+    on roles(:app) do
+      within release_path do
+        execute :rm, '-f public/remove-from-nginx'
+      end
+    end
+  end
+end
+
 # Default value for :format is :airbrussh.
 # set :format, :airbrussh
 

config/initializers/health_monitor.rb

@@ -2,6 +2,9 @@
 
 Rails.application.config.after_initialize do
   HealthMonitor.configure do |config|
+    config.file_absence.configure do |file_config|
+      file_config.filename = 'public/remove-from-nginx'
+    end
     # Make this health check available at /health
     config.path = :health