app: Convert health checks to use OKComputer

* The Alma patron fetch has been converted to a custom check.

* ActionMailer is checked for connectivity.

Note that this won't pass until emmahsax/okcomputer#21 is merged, because
the `:test` delivery method isn't recognised for the ActionMailer check.
Once it is merged, we can update the Gemfile to use the new version and
then the tests will pass.

Ref: AP-508

Author: awilfox

Gemfile

@@ -27,6 +27,7 @@ gem 'lograge', '>=0.11.2'
 gem 'mutex_m'
 gem 'netaddr', '~> 1.5', '>= 1.5.1'
 gem 'net-ssh'
+gem 'okcomputer', '~> 1.19'
 gem 'omniauth', '~> 1.9', '>= 1.9.2'
 gem 'omniauth-cas', '~> 2.0'
 gem 'pg', '~> 1.2'

Gemfile.lock

@@ -74,6 +74,7 @@ GEM
       execjs (~> 2)
     awesome_print (1.9.2)
     base64 (0.3.0)
+    benchmark (0.5.0)
     berkeley_library-alma (0.1.1)
       berkeley_library-logging (~> 0.2)
       berkeley_library-marc (~> 0.3.1)
@@ -258,6 +259,8 @@ GEM
     oj (3.16.11)
       bigdecimal (>= 3.0)
       ostruct (>= 0.2)
+    okcomputer (1.19.1)
+      benchmark
     omniauth (1.9.2)
       hashie (>= 3.4.6)
       rack (>= 1.6.2, < 3)
@@ -500,6 +503,7 @@ DEPENDENCIES
   mutex_m
   net-ssh
   netaddr (~> 1.5, >= 1.5.1)
+  okcomputer (~> 1.19)
   omniauth (~> 1.9, >= 1.9.2)
   omniauth-cas (~> 2.0)
   pg (~> 1.2)

app/controllers/home_controller.rb

@@ -3,14 +3,6 @@
 # We'll likely be asked to remove this at some point, but for now it's useful
 # to have in development.
 class HomeController < ApplicationController
-
-  # TODO: Move this to a HealthController that extends ActionController::API
-  #       - note: may involve extracting some of ApplicationController into a mixin
-  def health
-    check = Health::Check.new
-    render json: check, status: check.http_status_code
-  end
-
   def admin
     render :admin if require_framework_admin!
   end

app/lib/health/check.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+# Health check configuration
+
+OkComputer.logger = Rails.logger
+OkComputer.check_in_parallel = true
+
+class AlmaPatronCheck < OkComputer::Check
+  TEST_PATRON_ID = '012158720'
+
+  def check
+    Alma::User.find(TEST_PATRON_ID)
+    mark_message 'Success'
+  rescue StandardError => e
+    mark_failure
+    mark_message "Failed: #{e}"
+  end
+end
+
+# Ensure Alma API is working.
+OkComputer::Registry.register 'alma-patron-lookup', AlmaPatronCheck.new
+
+# Ensure database migrations have been run.
+OkComputer::Registry.register 'database-migrations', OkComputer::ActiveRecordMigrationsCheck.new
+
+# Ensure connectivity to the mail system.
+OkComputer::Registry.register 'action-mailer', OkComputer::ActionMailerCheck.new

app/lib/health/result.rb

@@ -2,7 +2,7 @@
   root to: redirect('/forms/altmedia/new')
 
   get 'admin', to: 'home#admin'
-  get 'health', to: 'home#health'
+  get 'health', to: 'ok_computer/ok_computer#index', defaults: { format: :json }
   get 'home', to: 'home#index'
   get 'build_info', to: 'home#build_info'