ConnectionHandler is a collection of ConnectionPool objects. It is used for keeping separate connection pools for ActiveRecord models that connect to different databases.

For example, suppose that you have 5 models, with the following hierarchy: 

 |
 +-- Book
 |    |
 |    +-- ScaryBook
 |    +-- GoodBook
 +-- Author
 +-- BankAccount

Suppose that Book is to connect to a separate database (i.e. one other than the default database). Then Book, ScaryBook and GoodBook will all use the same connection pool. Likewise, Author and BankAccount will use the same connection pool. However, the connection pool used by Author/BankAccount is not the same as the one used by Book/ScaryBook/GoodBook.

Normally there is only a single ConnectionHandler instance, accessible via ActiveRecord::Base.connection_handler. ActiveRecord models use this to determine that connection pool that they should use.

Methods
Public Class methods
new(pools = {})

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 287
287:       def initialize(pools = {})
288:         @connection_pools = pools
289:       end
Public Instance methods
clear_active_connections!()

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.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 302
302:       def clear_active_connections!
303:         @connection_pools.each_value {|pool| pool.release_connection }
304:       end
clear_all_connections!()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 311
311:       def clear_all_connections!
312:         @connection_pools.each_value {|pool| pool.disconnect! }
313:       end
clear_reloadable_connections!()

Clears the cache which maps classes

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 307
307:       def clear_reloadable_connections!
308:         @connection_pools.each_value {|pool| pool.clear_reloadable_connections! }
309:       end
connected?(klass)

Returns true if a connection that‘s accessible to this class has already been opened.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 331
331:       def connected?(klass)
332:         conn = retrieve_connection_pool(klass)
333:         conn ? conn.connected? : false
334:       end
connection_pools()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 291
291:       def connection_pools
292:         @connection_pools ||= {}
293:       end
establish_connection(name, spec)

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 295
295:       def establish_connection(name, spec)
296:         @connection_pools[name] = ConnectionAdapters::ConnectionPool.new(spec)
297:       end
remove_connection(klass)

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.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 340
340:       def remove_connection(klass)
341:         pool = @connection_pools[klass.name]
342:         @connection_pools.delete_if { |key, value| value == pool }
343:         pool.disconnect! if pool
344:         pool.spec.config if pool
345:       end
retrieve_connection_pool(klass)

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 347
347:       def retrieve_connection_pool(klass)
348:         pool = @connection_pools[klass.name]
349:         return pool if pool
350:         return nil if ActiveRecord::Base == klass
351:         retrieve_connection_pool klass.superclass
352:       end