From 81c95c419249a626fa72c735997cc7b1d0ea09a8 Mon Sep 17 00:00:00 2001
From: Trey Pendragon <tpendragon@princeton.edu>
Date: Thu, 14 Nov 2024 09:43:11 -0800
Subject: [PATCH] Add Capistrano task to remove application from the load
 balancer. (#1048)

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

Closes #1041

* Still log.
---
 Gemfile                               |  2 +-
 Gemfile.lock                          |  4 ++--
 config/deploy.rb                      | 31 +++++++++++++++++++++++++++
 config/initializers/health_monitor.rb |  7 +++++-
 4 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/Gemfile b/Gemfile
index 5e31c8359..1f92ec2d5 100644
--- a/Gemfile
+++ b/Gemfile
@@ -61,7 +61,7 @@ gem "datacite", github: "sul-dlss/datacite-ruby", branch: "main"
 gem "dogstatsd-ruby"
 gem "flipflop"
 gem "google-protobuf", "~> 3.25"
-gem "health-monitor-rails"
+gem "health-monitor-rails", "12.4.0"
 gem "honeybadger"
 gem "mailcatcher"
 gem "net-http-persistent"
diff --git a/Gemfile.lock b/Gemfile.lock
index ac31cd51c..e03627534 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -217,7 +217,7 @@ GEM
     google-protobuf (3.25.5-x86_64-linux)
     hashdiff (1.1.0)
     hashie (5.0.0)
-    health-monitor-rails (12.1.0)
+    health-monitor-rails (12.4.0)
       railties (>= 6.1)
     honeybadger (5.10.2)
     i18n (1.14.6)
@@ -557,7 +557,7 @@ DEPENDENCIES
   ffaker
   flipflop
   google-protobuf (~> 3.25)
-  health-monitor-rails
+  health-monitor-rails (= 12.4.0)
   honeybadger
   importmap-rails
   jbuilder
diff --git a/config/deploy.rb b/config/deploy.rb
index a725033ce..29386a3fd 100644
--- a/config/deploy.rb
+++ b/config/deploy.rb
@@ -21,6 +21,37 @@
 end
 after "deploy:log_revision", "write_version"
 
+namespace :application do
+  # You can/ should apply this command to a single host
+  # cap --hosts=tigerdata-staging1.lib.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=tigerdata-staging1.lib.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
+
 # rubocop:disable Rails/Output
 namespace :mailcatcher do
   desc "Opens Mailcatcher Consoles"
diff --git a/config/initializers/health_monitor.rb b/config/initializers/health_monitor.rb
index 1a2f81edc..c9cfbc51a 100644
--- a/config/initializers/health_monitor.rb
+++ b/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
     # Mediaflux check
     config.add_custom_provider(MediafluxStatus)
 
@@ -11,7 +14,9 @@
 
     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)
+        Honeybadger.notify(e)
+      end
     end
   end
 end