如何在Rails应用中配置多数据库

在Rails应用中配置多数据库可以通过以下步骤实现：

1. 在config/database.yml文件中定义多个数据库连接信息，例如：

default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: postgres
  password: password
  host: localhost

development:
  <<: *default
  database: myapp_development

test:
  <<: *default
  database: myapp_test

production:
  <<: *default
  database: myapp_production

other_database:
  <<: *default
  database: other_database

2. 在config/database.rb文件中配置多个数据库连接，例如：

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
config.active_record.railtie_name = "myapp"

config.databases = YAML.load_file(Rails.root.join('config', 'database.yml'))

config.databases.each do |name, db_config|
  config.database_configuration = db_config.with_indifferent_access

  ActiveRecord::Base.configurations[name.to_s] = config.database_configuration
end

3. 在models中定义多个数据库连接的模型，例如：

class User < ActiveRecord::Base
  establish_connection :development
end

class OtherModel < ActiveRecord::Base
  establish_connection :other_database
end

通过以上步骤，就可以在Rails应用中配置多个数据库连接，并在不同的模型中使用不同的数据库连接。