Read bookable slots from the replica

app/controllers/api/v1/bookable_slots_controller.rb

@@ -8,11 +8,13 @@ class InvalidScheduleType < StandardError; end
       end
 
       def index
-        @slots = BookableSlot.grouped(filtered_provider_ids, schedule_type, day)
+        ActiveRecord::Base.connected_to(role: :bookable_slots) do
+          @slots = BookableSlot.grouped(filtered_provider_ids, schedule_type, day)
 
-        Rails.logger.info("Empty times returned for #{day}") if day.present? && @slots.empty?
+          Rails.logger.info("Empty times returned for #{day}") if day.present? && @slots.empty?
 
-        render json: @slots
+          render json: @slots
+        end
       end
 
       private

app/controllers/bookable_slots_controller.rb

@@ -1,4 +1,6 @@
 class BookableSlotsController < ApplicationController
+  around_action :read_from_replica
+
   def index
     @bookable_slots = bookable_slots
 
@@ -51,6 +53,10 @@ def scoped_to_me?
 
   private
 
+  def read_from_replica(&block)
+    ActiveRecord::Base.connected_to(role: :bookable_slots, &block)
+  end
+
   def schedule_type
     params[:schedule_type]
   end

app/models/application_record.rb

@@ -1,3 +1,5 @@
 class ApplicationRecord < ActiveRecord::Base
   self.abstract_class = true
+
+  connects_to database: { writing: :primary, reading: :primary, bookable_slots: :secondary }
 end

config/database.yml

@@ -22,8 +22,13 @@ default: &default
   pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
 
 development:
-  <<: *default
-  database: telephone_appointment_planner_development
+  primary:
+    <<: *default
+    database: telephone_appointment_planner_development
+  secondary:
+    <<: *default
+    database: telephone_appointment_planner_development # just use the primary as a stand in here
+    replica: true
 
   # The specified database role being used to connect to postgres.
   # To create additional roles in postgres see `$ createuser --help`.
@@ -56,8 +61,22 @@ development:
 # re-generated from your development database when you run "rake".
 # Do not set this db to the same as development or production.
 test:
-  <<: *default
-  database: telephone_appointment_planner_test<%= ENV['TEST_ENV_NUMBER'] %>
+  primary:
+    <<: *default
+    database: telephone_appointment_planner_test
+  secondary:
+    <<: *default
+    database: telephone_appointment_planner_test
+    replica: true
+
+staging:
+  primary:
+    <<: *default
+    url: <%= ENV['DATABASE_URL'] %>
+  secondary:
+    <<: *default
+    url: <%= ENV['DATABASE_URL'] %> # use this as a stand-in for now
+    replica: true
 
 # As with config/secrets.yml, you never want to store sensitive information,
 # like your database password, in your source code. If your source code is
@@ -79,5 +98,10 @@ test:
 #     url: <%= ENV['DATABASE_URL'] %>
 #
 production:
-  <<: *default
-  url: <%= ENV['DATABASE_URL'] %>
+  primary:
+    <<: *default
+    url: <%= ENV['DATABASE_URL'] %>
+  secondary:
+    <<: *default
+    url: <%= Rails.env.production? ? ENV['SECONDARY_DATABASE_URL'] : ENV['DATABASE_URL'] %>
+    replica: true