class ActiveRecord::ConnectionAdapters::ConnectionPool

def initialize(spec)

The default ConnectionPool maximum size is 5.

this ConnectionPool.
host name, username, password, etc), as well as the maximum size for
object which describes database connection information (e.g. adapter,
Creates a new ConnectionPool object. +spec+ is a ConnectionSpecification 
def initialize(spec)
  super()
  @spec = spec
  @checkout_timeout = spec.config[:checkout_timeout] || 5
  @dead_connection_timeout = spec.config[:dead_connection_timeout] || 5
  @reaper  = Reaper.new self, spec.config[:reaping_frequency]
  @reaper.run
  # default max pool size to 5
  @size = (spec.config[:pool] && spec.config[:pool].to_i) || 5
  # The cache of reserved connections mapped to threads
  @reserved_connections = ThreadSafe::Cache.new(:initial_capacity => @size)
  @connections         = []
  @automatic_reconnect = true
  @available = Queue.new self
end