feat: handle if read_replica is not available

app/models/application_record.rb

@@ -2,7 +2,7 @@ class ApplicationRecord < ActiveRecord::Base
   include Events::Types
   self.abstract_class = true
 
-  connects_to database: { writing: :primary, reading: :primary_replica }
+  # connects_to database: { writing: :primary, reading: :primary_replica }
 
   before_validation :validates_column_content_length
 

config/initializers/database_fallback.rb

@@ -0,0 +1,15 @@
+require 'active_record'
+
+replica_available = ActiveRecord::Base.connection_pool.with_connection do |conn|
+  conn.execute('SELECT 1 FROM primary_replica LIMIT 1')
+  true
+rescue StandardError
+  false
+end
+
+Rails.application.config.to_prepare do
+  ApplicationRecord.connects_to database: {
+    writing: :primary,
+    reading: replica_available ? :primary_replica : :primary
+  }
+end