A few months ago, when I migrated BookJetty from Java to Ruby On Rails (RoR) platform, one obstacle I faced was I could not find any object pooling library that checks for idle objects on a fixed interval, and evicts invalid and expired objects in the pool.

While in Java I used Apache Commons Pool, in Ruby, I was scratching my head back then.

But, the beauty of Ruby-and-Rails world is the citizen love to hack, when they can’t find a way, well, they always hack a way out. So being a good citizen wannabe, I wrote the Ruby version of first-in-first-out (FIFO) object pool library inspired by Apache Commons Pool.

It currently supports the following configuration parameters:

• min_idle
• max_idle
• max_idle_time
• max_active
• timeout
• validation_timeout
• idle_check_no_per_run
• idle_check_interval

This morning I’ve just got the time to wrap it up as a gem. To get started:

$ gem install common-pool

And some code snippets:

require 'common_pool'    
  
# Extend data source object
class RandomNumberDataSource < CommonPool::PoolDataSource
  # Overwrite to return object to be stored in the pool.
  def create_object
    rand(1000)
  end
    
  # Overwrite to check if idle object in the pool is still valid.
  def valid?(object)
    true
  end
end
  
# Create a new object pool
object_pool = ObjectPool.new(RandomNumberDataSource.new)
  
# Borrow object from the pool
object = object_pool.borrow_object

# Return object to the pool
object_pool.return_object(object)
  
# Or invalidate object and remove it from the pool
object_pool.invalidate_object(object)
  
# Create object pool with idle objects eviction thread
object_pool = ObjectPool.new(RandomNumberDataSource.new) do |config|
  config.min_idle = 5
  config.max_idle = 10
  
  # max 10 idle objects checked per run
  config.idle_check_no_per_run = 10

  # check idle objects every 10 minutes
  config.idle_check_interval = 10 * 60
end

# Return a hash of pool instance status variables, i.e.
# active and idle lists size, and configuration options
object_pool.status_info

For more information, visit common-pool rdoc documentation.