Class: ActiveRecord::ConnectionAdapters::ConnectionHandler
- Inherits:
-
Object
- Object
- ActiveRecord::ConnectionAdapters::ConnectionHandler
- Defined in:
- lib/active_record/connection_adapters/abstract/connection_pool.rb
Overview
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 ActiveRecord::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 knowlodge about the model. The model needs to pass a specification name to the handler, in order to lookup the correct connection pool.
Instance Method Summary collapse
-
#active_connections? ⇒ Boolean
Returns true if there are any active connections among the connection pools that the ConnectionHandler is managing.
-
#clear_active_connections! ⇒ Object
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! ⇒ Object
-
#clear_reloadable_connections! ⇒ Object
Clears the cache which maps classes.
-
#connected?(spec_name) ⇒ Boolean
Returns true if a connection that’s accessible to this class has already been opened.
- #connection_pool_list ⇒ Object (also: #connection_pools)
- #establish_connection(config) ⇒ Object
-
#initialize ⇒ ConnectionHandler
constructor
A new instance of ConnectionHandler.
-
#remove_connection(spec_name) ⇒ Object
Remove the connection for this class.
-
#retrieve_connection(spec_name) ⇒ Object
Locate the connection of the nearest super class.
-
#retrieve_connection_pool(spec_name) ⇒ Object
Retrieving the connection pool happens a lot, so we cache it in @owner_to_pool.
Constructor Details
#initialize ⇒ ConnectionHandler
Returns a new instance of ConnectionHandler.
868 869 870 871 872 873 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 868 def initialize # These caches are keyed by spec.name (ConnectionSpecification#name). @owner_to_pool = Concurrent::Map.new(initial_capacity: 2) do |h, k| h[k] = Concurrent::Map.new(initial_capacity: 2) end end |
Instance Method Details
#active_connections? ⇒ Boolean
Returns true if there are any active connections among the connection pools that the ConnectionHandler is managing.
904 905 906 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 904 def active_connections? connection_pool_list.any?(&:active_connection?) end |
#clear_active_connections! ⇒ Object
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.
911 912 913 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 911 def clear_active_connections! connection_pool_list.each(&:release_connection) end |
#clear_all_connections! ⇒ Object
922 923 924 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 922 def clear_all_connections! connection_pool_list.each(&:disconnect!) end |
#clear_reloadable_connections! ⇒ Object
Clears the cache which maps classes.
See ConnectionPool#clear_reloadable_connections! for details.
918 919 920 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 918 def clear_reloadable_connections! connection_pool_list.each(&:clear_reloadable_connections!) end |
#connected?(spec_name) ⇒ Boolean
Returns true if a connection that’s accessible to this class has already been opened.
940 941 942 943 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 940 def connected?(spec_name) conn = retrieve_connection_pool(spec_name) conn && conn.connected? end |
#connection_pool_list ⇒ Object Also known as: connection_pools
875 876 877 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 875 def connection_pool_list owner_to_pool.values.compact end |
#establish_connection(config) ⇒ Object
880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 880 def establish_connection(config) resolver = ConnectionSpecification::Resolver.new(Base.configurations) spec = resolver.spec(config) remove_connection(spec.name) = ActiveSupport::Notifications.instrumenter payload = { connection_id: object_id } if spec payload[:spec_name] = spec.name payload[:config] = spec.config end .instrument("!connection.active_record", payload) do owner_to_pool[spec.name] = ConnectionAdapters::ConnectionPool.new(spec) end owner_to_pool[spec.name] end |
#remove_connection(spec_name) ⇒ Object
Remove the connection for this class. This will close the active connection and the defined connection (if they exist). The result can be used as an argument for #establish_connection, for easily re-establishing the connection.
949 950 951 952 953 954 955 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 949 def remove_connection(spec_name) if pool = owner_to_pool.delete(spec_name) pool.automatic_reconnect = false pool.disconnect! pool.spec.config end end |
#retrieve_connection(spec_name) ⇒ Object
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).
930 931 932 933 934 935 936 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 930 def retrieve_connection(spec_name) #:nodoc: pool = retrieve_connection_pool(spec_name) raise ConnectionNotEstablished, "No connection pool with '#{spec_name}' found." unless pool conn = pool.connection raise ConnectionNotEstablished, "No connection for '#{spec_name}' in connection pool" unless conn conn end |
#retrieve_connection_pool(spec_name) ⇒ Object
Retrieving the connection pool happens a lot, so we cache it in @owner_to_pool. This makes retrieving the connection pool O(1) once the process is warm. When a connection is established or removed, we invalidate the cache.
960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 |
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 960 def retrieve_connection_pool(spec_name) owner_to_pool.fetch(spec_name) do # Check if a connection was previously established in an ancestor process, # which may have been forked. if ancestor_pool = pool_from_any_process_for(spec_name) # A connection was established in an ancestor process that must have # subsequently forked. We can't reuse the connection, but we can copy # the specification and establish a new connection with it. establish_connection(ancestor_pool.spec.to_hash).tap do |pool| pool.schema_cache = ancestor_pool.schema_cache if ancestor_pool.schema_cache end else owner_to_pool[spec_name] = nil end end end |