PgHero gem error "No connection pool for 'PgHero::Connection::Database337600' found."

Question

I'm using RubyOnRails 6.1 with multiDB setup: primary and follower. CustomDatabaseResolver is configured to distribute load between databases.

class CustomDatabaseResolver < ActiveRecord::Middleware::DatabaseSelector::Resolver
  def read_from_primary?
    super || rand(2).zero?
  end
end

I think this configuration creates a problem for pgHero gem because its dashboard is randomly crashing with the error:

ActiveRecord::ConnectionNotEstablished
No connection pool for 'PgHero::Connection::Database337600' found.

I cannot find a way this can be fixed. I have tried to force pgHero controller to use primary, but no luck.

# config/initializers/pghero.rb
Rails.application.reloader.to_prepare do
  PgHero::HomeController.send :include, WriterDbRoleExecutor
end

# app/controllers/concerns/writer_db_role_executor.rb
module WriterDbRoleExecutor
  extend ActiveSupport::Concern

  included do
    around_action { |_controller, action| ApplicationRecord.force_writer_db_role(&action) }
  end
end

Btw, same approach did helped with another gem - blazer

Rails.application.reloader.to_prepare do
  Blazer::BaseController.send :include, WriterDbRoleExecutor
end

Answer 1

This actually got fixed by prepending around action:

prepend_around_action { |_controller, action| ApplicationRecord.force_writer_db_role(&action) }

There are some controller callbacks in PgHero::HomeController that make db connections, and we should ensure our callback got fired first.