Add capistrano task to remove application from the load balancer. (#716)

Closes #715

Gemfile

@@ -15,7 +15,7 @@ gem 'bootstrap', '~> 4.0'
 gem 'devise'
 gem 'devise-guests', '~> 0.6'
 gem 'faraday_middleware'
-gem 'health-monitor-rails'
+gem 'health-monitor-rails', '12.4.0'
 gem 'honeybadger'
 gem 'httparty'
 gem 'jbuilder', '~> 2.7'

Gemfile.lock

@@ -240,7 +240,7 @@ GEM
       activesupport (>= 6.1)
     hashdiff (1.1.1)
     hashie (5.0.0)
-    health-monitor-rails (12.3.0)
+    health-monitor-rails (12.4.0)
       railties (>= 6.1)
     honeybadger (5.16.0)
       logger
@@ -636,7 +636,7 @@ DEPENDENCIES
   ed25519
   faraday_middleware
   foreman
-  health-monitor-rails
+  health-monitor-rails (= 12.4.0)
   honeybadger
   httparty
   jbuilder (~> 2.7)

config/deploy.rb

@@ -30,6 +30,36 @@
 # Uncomment to re-index on every deploy. Only needed when we're actively
 # updating how indexing happens.
 # after "deploy:published", "pdc_discovery:reindex"
+namespace :application do
+  # You can/ should apply this command to a single host
+  # cap --hosts=pdc-discovery-staging1.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=pdc-discovery-staging1.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
 
 namespace :mailcatcher do
   desc "Opens Mailcatcher Consoles"
@@ -47,4 +77,4 @@
       end
     end
   end
-end
+end

config/initializers/health_monitor.rb

@@ -3,6 +3,9 @@
   HealthMonitor.configure do |config|
     config.cache
 
+    config.file_absence.configure do |file_config|
+      file_config.filename = "public/remove-from-nginx"
+    end
     config.solr.configure do |c|
       c.url = Blacklight.default_index.connection.uri.to_s
       c.collection = Blacklight.default_index.connection.uri.path.split("/").last
@@ -12,8 +15,10 @@
     config.path = :health
 
     config.error_callback = proc do |e|
-      Rails.logger.error "Health check failed with: #{e.message}"
-      Honeybadger.notify(e)
+      unless e.is_a?(HealthMonitor::Providers::FileAbsenceException)
+        Rails.logger.error "Health check failed with: #{e.message}"
+        Honeybadger.notify(e)
+      end
     end
   end
 end