Improved healtcheck, which checks if the app is running and also if t…

…he connections to databases are established

app/controllers/health_controller.rb

@@ -1,5 +1,44 @@
 class HealthController < ApplicationController
+
   def index
-    head :ok
+    database_check_results = check_db_connections
+    if all_database_healthy?(database_check_results)
+      render json: {status: "ok", databases: database_check_results}, status: :ok
+    else
+      render json: {status: "error", databases: database_check_results}, status: :internal_server_error
+    end
+  end
+
+  private
+  def all_database_healthy?(database_check_results)
+    database_check_results.values.all? { |status| status[:status] == "ok" }
+  end
+
+  def check_db_connections
+    db_status = {}
+    databases.each do |role, connection|
+      db_status[role] = perform_health_check(connection)
+    ensure
+      ActiveRecord::Base.clear_active_connections!
+    end
+    db_status
+  end
+
+  def databases
+    {
+      primary: ActiveRecord::Base.connected_to(role: :writing) { ApplicationRecord.connection },
+      datahub: ActiveRecord::Base.connected_to(role: :reading) { DatahubRecord.connection }
+    }
+  end
+
+  def perform_health_check(connection)
+    if connection
+      connection.execute('SELECT 1')
+      {status: 'ok'}
+    else
+      {status: 'error', message: 'Connection not established'}
+    end
+  rescue => e
+    {status: 'error', message: e.message}
   end
 end