Class: ActiveRecord::ConnectionAdapters::ConnectionHandler
Relationships & Source Files | |
Inherits: | Object |
Defined in: | activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb |
Overview
Active Record Connection Handler
ConnectionHandler
is a collection of ConnectionPool
objects. It is used for keeping separate connection pools that connect to different databases.
For example, suppose that you have 5 models, with the following hierarchy:
class Author < ActiveRecord::Base
end
class BankAccount < ActiveRecord::Base
end
class Book < ActiveRecord::Base
establish_connection :library_db
end
class ScaryBook < Book
end
class GoodBook < Book
end
And a database.yml that looked like this:
development:
database: my_application
host: localhost
library_db:
database: library
host: some.library.org
Your primary database in the development environment is “my_application” but the Book model connects to a separate database called “library_db” (this can even be a database on a different machine).
Book, ScaryBook, and GoodBook will all use the same connection pool to “library_db” while Author, BankAccount, and any other models you create will use the default connection pool to “my_application”.
The various connection pools are managed by a single instance of ConnectionHandler
accessible via Base.connection_handler. All Active Record models use this handler to determine the connection pool that they should use.
The ConnectionHandler class is not coupled with the Active models, as it has no knowledge about the model. The model needs to pass a connection specification name to the handler, in order to look up the correct connection pool.
Constant Summary
-
FINALIZER =
private
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 58lambda { |_| ActiveSupport::ForkTracker.check! }
Class Method Summary
- .new ⇒ ConnectionHandler constructor
Instance Method Summary
-
#active_connections?(role = nil) ⇒ Boolean
Returns true if there are any active connections among the connection pools that the
ConnectionHandler
is managing. - #all_connection_pools
-
#clear_active_connections!(role = nil)
Returns any connections in use by the current thread back to the pool, and also returns connections to the pool cached by threads that are no longer alive.
- #clear_all_connections!(role = nil)
-
#clear_reloadable_connections!(role = nil)
Clears the cache which maps classes.
-
#connected?(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard) ⇒ Boolean
Returns true if a connection that’s accessible to this class has already been opened.
-
#connection_pool_list(role = nil)
(also: #connection_pools)
Returns the pools for a connection handler and given role.
-
#connection_pools(role = nil)
Alias for #connection_pool_list.
- #establish_connection(config, owner_name: Base, role: Base.current_role, shard: Base.current_shard, clobber: false)
-
#flush_idle_connections!(role = nil)
Disconnects all currently idle connections.
- #remove_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)
-
#retrieve_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)
Retrieving the connection pool happens a lot, so we cache it in @connection_name_to_pool_manager.
Constructor Details
.new ⇒ ConnectionHandler
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 77
def initialize # These caches are keyed by pool_config.connection_name (PoolConfig#connection_name). @connection_name_to_pool_manager = Concurrent::Map.new(initial_capacity: 2) # Backup finalizer: if the forked child skipped Kernel#fork the early discard has not occurred ObjectSpace.define_finalizer self, FINALIZER end
Instance Method Details
#active_connections?(role = nil) ⇒ Boolean
Returns true if there are any active connections among the connection pools that the ConnectionHandler
is managing.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 173
def active_connections?(role = nil) if role.nil? deprecation_for_pool_handling(__method__) role = ActiveRecord::Base.current_role end each_connection_pool(role).any?(&:active_connection?) end
#all_connection_pools
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 97
def all_connection_pools ActiveRecord.deprecator.warn(<<-MSG.squish) The `all_connection_pools` method is deprecated in favor of `connection_pool_list`. Call `connection_pool_list(:all)` to get the same behavior as `all_connection_pools`. MSG connection_name_to_pool_manager.values.flat_map { |m| m.pool_configs.map(&:pool) } end
#clear_active_connections!(role = nil)
Returns any connections in use by the current thread back to the pool, and also returns connections to the pool cached by threads that are no longer alive.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 185
def clear_active_connections!(role = nil) if role.nil? deprecation_for_pool_handling(__method__) role = ActiveRecord::Base.current_role end each_connection_pool(role).each(&:release_connection) end
#clear_all_connections!(role = nil)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 206
def clear_all_connections!(role = nil) if role.nil? deprecation_for_pool_handling(__method__) role = ActiveRecord::Base.current_role end each_connection_pool(role).each(&:disconnect!) end
#clear_reloadable_connections!(role = nil)
Clears the cache which maps classes.
See ConnectionPool#clear_reloadable_connections! for details.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 197
def clear_reloadable_connections!(role = nil) if role.nil? deprecation_for_pool_handling(__method__) role = ActiveRecord::Base.current_role end each_connection_pool(role).each(&:clear_reloadable_connections!) end
#connected?(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard) ⇒ Boolean
Returns true if a connection that’s accessible to this class has already been opened.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 251
def connected?(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard) pool = retrieve_connection_pool(connection_name, role: role, shard: shard) pool && pool.connected? end
#connection_pool_list(role = nil) Also known as: #connection_pools
Returns the pools for a connection handler and given role. If :all
is passed, all pools belonging to the connection handler will be returned.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 107
def connection_pool_list(role = nil) if role.nil? deprecation_for_pool_handling(__method__) role = ActiveRecord::Base.current_role connection_name_to_pool_manager.values.flat_map { |m| m.pool_configs(role).map(&:pool) } elsif role == :all connection_name_to_pool_manager.values.flat_map { |m| m.pool_configs.map(&:pool) } else connection_name_to_pool_manager.values.flat_map { |m| m.pool_configs(role).map(&:pool) } end end
#connection_pools(role = nil)
Alias for #connection_pool_list.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 118
alias :connection_pools :connection_pool_list
#establish_connection(config, owner_name: Base, role: Base.current_role, shard: Base.current_shard, clobber: false)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 131
def establish_connection(config, owner_name: Base, role: Base.current_role, shard: Base.current_shard, clobber: false) owner_name = determine_owner_name(owner_name, config) pool_config = resolve_pool_config(config, owner_name, role, shard) db_config = pool_config.db_config pool_manager = set_pool_manager(pool_config.connection_name) # If there is an existing pool with the same values as the pool_config # don't remove the connection. Connections should only be removed if we are # establishing a connection on a class that is already connected to a different # configuration. existing_pool_config = pool_manager.get_pool_config(role, shard) if !clobber && existing_pool_config && existing_pool_config.db_config == db_config # Update the pool_config's connection class if it differs. This is used # for ensuring that ActiveRecord::Base and the primary_abstract_class use # the same pool. Without this granular swapping will not work correctly. if owner_name.primary_class? && (existing_pool_config.connection_class != owner_name) existing_pool_config.connection_class = owner_name end existing_pool_config.pool else disconnect_pool_from_pool_manager(pool_manager, role, shard) pool_manager.set_pool_config(role, shard, pool_config) payload = { connection_name: pool_config.connection_name, role: role, shard: shard, config: db_config.configuration_hash } ActiveSupport::Notifications.instrumenter.instrument("!connection.active_record", payload) do pool_config.pool end end end
#flush_idle_connections!(role = nil)
Disconnects all currently idle connections.
See ConnectionPool#flush! for details.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 218
def flush_idle_connections!(role = nil) if role.nil? deprecation_for_pool_handling(__method__) role = ActiveRecord::Base.current_role end each_connection_pool(role).each(&:flush!) end
#remove_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 256
def remove_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard) if pool_manager = get_pool_manager(connection_name) disconnect_pool_from_pool_manager(pool_manager, role, shard) end end
#retrieve_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)
Retrieving the connection pool happens a lot, so we cache it in @connection_name_to_pool_manager. This makes retrieving the connection pool O(1) once the process is warm. When a connection is established or removed, we invalidate the cache.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 265
def retrieve_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard) pool_config = get_pool_manager(connection_name)&.get_pool_config(role, shard) pool_config&.pool end