Utilize FileAbsenceCheck to force the loabalancer to remove a host

Gemfile

@@ -7,7 +7,7 @@ gem "amazing_print"
 gem "aws-sdk-s3"
 gem "datacite-mapping"
 gem "dogstatsd-ruby"
-gem "health-monitor-rails"
+gem "health-monitor-rails", github: "pulibrary/health-monitor-rails", branch: "add-file-absence-check"
 gem "honeybadger"
 gem "io-wait", "0.2.1"
 gem "net-ftp"

Gemfile.lock

@@ -7,6 +7,14 @@ GIT
       hashie (~> 3.4, >= 3.4.3)
       nokogiri
 
+GIT
+  remote: https://github.com/pulibrary/health-monitor-rails.git
+  revision: 69f1ded751c5fa2f0b6a0f1c2180cbd832a41365
+  branch: add-file-absence-check
+  specs:
+    health-monitor-rails (12.3.0)
+      railties (>= 6.1)
+
 GIT
   remote: https://github.com/sul-dlss/datacite-ruby.git
   revision: e17b5eb313aa8cfa7a345efb71c98bb51d660a9f
@@ -245,15 +253,13 @@ GEM
       activesupport (>= 6.1)
     hashdiff (1.1.1)
     hashie (3.6.0)
-    health-monitor-rails (12.3.0)
-      railties (>= 6.1)
     honeybadger (5.15.6)
     i18n (1.14.6)
       concurrent-ruby (~> 1.0)
     ice_nine (0.11.2)
     io-console (0.7.2)
     io-wait (0.2.1)
-    irb (1.14.0)
+    irb (1.14.1)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
     jbuilder (2.13.0)
@@ -276,7 +282,7 @@ GEM
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     logger (1.6.1)
-    loofah (2.22.0)
+    loofah (2.23.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
     mail (2.8.1)
@@ -373,7 +379,7 @@ GEM
       rack (< 3)
     rack-test (2.1.0)
       rack (>= 1.3)
-    rackup (1.0.0)
+    rackup (1.0.1)
       rack (< 3)
       webrick
     rails (7.2.1.1)
@@ -577,7 +583,7 @@ GEM
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
-    webrick (1.8.2)
+    webrick (1.9.0)
     websocket (1.2.11)
     websocket-driver (0.7.6)
       websocket-extensions (>= 0.1.0)
@@ -628,7 +634,7 @@ DEPENDENCIES
   ffaker
   foreman
   friendly_id (~> 5.4.0)
-  health-monitor-rails
+  health-monitor-rails!
   honeybadger
   io-wait (= 0.2.1)
   jbuilder (~> 2.7)

config/deploy.rb

@@ -79,6 +79,35 @@
       end
     end
   end
+
+  # You can/ should apply this command to a single host
+  # cap --hosts=pdc-describe-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 > 1
+      raise "You must run this command on individual 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-describe-staging1.princeton.edu staging application:serve_from_nginx
+  desc "Marks the server(s) to be removed from 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
 
 before "deploy:reverted", "deploy:assets:precompile"

config/initializers/health_monitor.rb

@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 HealthMonitor.configure do |config|
   config.cache
   config.redis
@@ -13,8 +14,12 @@
     sidekiq_config.critical = false
   end
 
+  config.file_absence.configure do |file_config|
+    file_config.filename = "public/remove-from-nginx"
+  end
+
   config.error_callback = proc do |e|
     Rails.logger.error "Health check failed with: #{e.message}"
-    Honeybadger.notify(e)
+    Honeybadger.notify(e) unless e.is_a?(HealthMonitor::Providers::FileAbsenceException)
   end
 end