drbrain
commented
10 years ago Example of a multi-connection pool:
require 'connection_pool/timed_stack'
class ConnectionPool::TimedStackMulti < ConnectionPool::TimedStack
def initialize(size = 0, &block)
super
@enqueued = 0
@ques = Hash.new { |h, k| h[k] = [] }
@lru = {}
@key = :"connection_args-#{object_id}"
end
def empty?
(@created - @enqueued) >= @max
end
def length
@max - @created + @enqueued
end
def pop connection_args, timeout = 0.5
Thread.current[@key] = connection_args
super timeout
end
def push(connection_args, obj)
Thread.current[@key] = connection_args
super(obj)
end
private
def connection_stored? # :nodoc:
connection_args = Thread.current[@key]
!@ques[connection_args].empty?
end
def fetch_connection # :nodoc:
connection_args = Thread.current[@key]
@enqueued -= 1
lru_update connection_args
@ques[connection_args].pop
end
def lru_update(connection_args) # :nodoc:
@lru.delete connection_args
@lru[connection_args] = true
end
def shutdown_connections # :nodoc:
@ques.each_key do |key|
Thread.current[@key] = key
super
end
end
def store_connection(obj) # :nodoc:
connection_args = Thread.current[@key]
@ques[connection_args].push obj
@enqueued += 1
end
def try_create # :nodoc:
connection_args = Thread.current[@key]
if @created >= @max && @enqueued >= 1
oldest, = @lru.first
@lru.delete oldest
@ques[oldest].pop
@created -= 1
end
if @created < @max
@created += 1
lru_update connection_args
return @create_block.call(connection_args)
end
end
end
mperham
This makes TimedStack extendable for use by multiple connections. For multiple connections the resource managed is the number of file descriptors used instead of the number of connections to a particular service.
A subclass can use thread local variables to pass extra arguments down without altering the calls which, while clumsy, is functional.