Class: ActiveRecord::ConnectionAdapters::ConnectionHandler
Relationships & Source Files | |
Namespace Children | |
Classes:
| |
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.
Class Method Summary
- .new ⇒ ConnectionHandler constructor
Instance Attribute Summary
- #connection_name_to_pool_manager readonly private
- #prevent_writes rw Internal use only
- #prevent_writes=(prevent_writes) rw Internal use only
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. -
#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, strict: false)
Retrieving the connection pool happens a lot, so we cache it in @connection_name_to_pool_manager.
- #determine_owner_name(owner_name, config) private
- #disconnect_pool_from_pool_manager(pool_manager, role, shard) private
-
#get_pool_manager(connection_name)
private
Returns the pool manager for a connection name / identifier.
- #pool_managers private
-
#resolve_pool_config(config, connection_name, role, shard)
private
Returns an instance of
PoolConfig
for a given adapter. -
#set_pool_manager(connection_name)
private
Get the existing pool manager or initialize and assign a new one.
- #connection_pool_names Internal use only
- #each_connection_pool(role = nil, &block) Internal use only
-
#retrieve_connection(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)
Internal use only
Locate the connection of the nearest super class.
Constructor Details
.new ⇒ ConnectionHandler
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 73
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) end
Instance Attribute Details
#connection_name_to_pool_manager (readonly, private)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 237
attr_reader :connection_name_to_pool_manager
#prevent_writes (rw)
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 78
def prevent_writes # :nodoc: ActiveSupport::IsolatedExecutionState[:active_record_prevent_writes] end
#prevent_writes=(prevent_writes) (rw)
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 82
def prevent_writes=(prevent_writes) # :nodoc: ActiveSupport::IsolatedExecutionState[:active_record_prevent_writes] = prevent_writes 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 154
def active_connections?(role = nil) each_connection_pool(role).any?(&:active_connection?) 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 161
def clear_active_connections!(role = nil) each_connection_pool(role).each do |pool| pool.release_connection pool.disable_query_cache! end end
#clear_all_connections!(role = nil)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 175
def clear_all_connections!(role = nil) 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 171
def clear_reloadable_connections!(role = nil) 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 197
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 92
def connection_pool_list(role = nil) if role.nil? || 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_pool_names
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 86
def connection_pool_names # :nodoc: connection_name_to_pool_manager.keys end
#connection_pools(role = nil)
Alias for #connection_pool_list.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 99
alias :connection_pools :connection_pool_list
#determine_owner_name(owner_name, config) (private)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 279
def determine_owner_name(owner_name, config) if owner_name.is_a?(String) || owner_name.is_a?(Symbol) StringConnectionName.new(owner_name.to_s) elsif config.is_a?(Symbol) StringConnectionName.new(config.to_s) else owner_name end end
#disconnect_pool_from_pool_manager(pool_manager, role, shard) (private)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 253
def disconnect_pool_from_pool_manager(pool_manager, role, shard) pool_config = pool_manager.remove_pool_config(role, shard) if pool_config pool_config.disconnect! pool_config.db_config end end
#each_connection_pool(role = nil, &block)
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 101
def each_connection_pool(role = nil, &block) # :nodoc: role = nil if role == :all return enum_for(__method__, role) unless block_given? connection_name_to_pool_manager.each_value do |manager| manager.each_pool_config(role) do |pool_config| yield pool_config.pool end end end
#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 112
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 182
def flush_idle_connections!(role = nil) each_connection_pool(role).each(&:flush!) end
#get_pool_manager(connection_name) (private)
Returns the pool manager for a connection name / identifier.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 240
def get_pool_manager(connection_name) connection_name_to_pool_manager[connection_name] end
#pool_managers (private)
[ GitHub ]# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 249
def pool_managers connection_name_to_pool_manager.values 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 202
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
#resolve_pool_config(config, connection_name, role, shard) (private)
Returns an instance of PoolConfig
for a given adapter. Accepts a hash one layer deep that contains all connection information.
Example
config = { "production" => { "host" => "localhost", "database" => "foo", "adapter" => "sqlite3" } }
pool_config = Base.configurations.resolve_pool_config(:production)
pool_config.db_config.configuration_hash
# => { host: "localhost", database: "foo", adapter: "sqlite3" }
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 272
def resolve_pool_config(config, connection_name, role, shard) db_config = Base.configurations.resolve(config) db_config.validate! raise(AdapterNotSpecified, "database configuration does not specify adapter") unless db_config.adapter ConnectionAdapters::PoolConfig.new(connection_name, db_config, role, shard) end
#retrieve_connection(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)
Locate the connection of the nearest super class. This can be an active or defined connection: if it is the latter, it will be opened and set as the active connection for the class it was defined for (not necessarily the current class).
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 190
def retrieve_connection(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard) # :nodoc: pool = retrieve_connection_pool(connection_name, role: role, shard: shard, strict: true) pool.lease_connection end
#retrieve_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard, strict: false)
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 211
def retrieve_connection_pool(connection_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard, strict: false) pool_manager = get_pool_manager(connection_name) pool = pool_manager&.get_pool_config(role, shard)&.pool if strict && !pool selector = [ ("'#{shard}' shard" unless shard == ActiveRecord::Base.default_shard), ("'#{role}' role" unless role == ActiveRecord::Base.default_role), ].compact.join(" and ") selector = [ (connection_name unless connection_name == "ActiveRecord::Base"), selector.presence, ].compact.join(" with ") selector = " for #{selector}" if selector.present? = "No database connection defined#{selector}." raise ConnectionNotDefined.new(, connection_name: connection_name, shard: shard, role: role) end pool end
#set_pool_manager(connection_name) (private)
Get the existing pool manager or initialize and assign a new one.
# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb', line 245
def set_pool_manager(connection_name) connection_name_to_pool_manager[connection_name] ||= PoolManager.new end