I have just finished following RoR Multiple Databases with Active Record however, my Rails app still seems to be completely ignoring my read replica configuration. In fact, I specifically made a typo in the hostname and have never been able to trigger an error yet on reading from the read replica.

Here's my config/initializers/multi_db.rb file:

Rails.application.configure do
  config.active_record.database_selector = { delay: 2.seconds }
  config.active_record.database_resolver = ActiveRecord::Middleware::DatabaseSelector::Resolver
  config.active_record.database_resolver_context = ActiveRecord::Middleware::DatabaseSelector::Resolver::Session
end

My config/database.yml file:

development:
  primary:
    <<: *default
    host: <%= Rails.application.credentials.development[:host] %>
    username: <%= Rails.application.credentials.development[:username] %>
    password: <%= Rails.application.credentials.development[:password] %>
    database: <%= Rails.application.credentials.development[:database] %>
  primary_replica:
    <<: *default
    host: aurora-prod-test.cluster-rox-.us-west-2.rds.amazonaws.com
    username: <%= Rails.application.credentials.development[:username] %>
    password: <%= Rails.application.credentials.development[:password] %>
    database: <%= Rails.application.credentials.development[:database] %>
    replica: true

And in my app/models/application_record.rb file, I have specified:

connects_to database: { writing: :primary, reading: :primary_replica }

According to the article, that seems to be it. However, when I try a basic GET request, it doesn't seem to use the read replica. I have a typo in the name where it shows 'rox' instead of 'ro' and I'm not experiencing any errors, indicating that the read replica is not working properly.

CodePudding user response：

Turns out this is a bug in Rails: https://github.com/rails/rails/issues/45162

Was able to get it fixed by adding the code that belonged in config/initializers/multi_db.rb into my config/application.rb file instead.