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Class: ActiveRecord::ConnectionAdapters::ConnectionPool::Queue

Overview

Threadsafe, fair, FIFO queue. Meant to be used by ::ActiveRecord::ConnectionAdapters::ConnectionPool with which it shares a Monitor. But could be a generic Queue.

The Queue in stdlib's 'thread' could replace this class except stdlib's doesn't support waiting with a timeout.

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(lock = Monitor.new) ⇒ Queue

[ GitHub ] 

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb', line 74



def initialize(lock = Monitor.new)
  @lock = lock
  @cond = @lock.new_cond
  @num_waiting = 0
  @queue = []
end


  







Instance Attribute Details



  

    #any_waiting?  ⇒ Boolean  (readonly)
  



  

    

Test if any threads are currently waiting on the queue.


  





  


  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb', line 82



def any_waiting?
  synchronize do
    @num_waiting > 0
  end
end


  







Instance Method Details



  

    #add(element)  
  



  

    

Add element to the queue.  Never blocks.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb', line 97



def add(element)
  synchronize do
    @queue.push element
    @cond.signal
  end
end


  








  

    #clear  
  



  

    

Remove all elements from the queue.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb', line 112



def clear
  synchronize do
    @queue.clear
  end
end


  








  

    #delete(element)  
  



  

    

If element is in the queue, remove and return it, or nil.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb', line 105



def delete(element)
  synchronize do
    @queue.delete(element)
  end
end


  








  

    #num_waiting  
  



  

    

Returns the number of threads currently waiting on this queue.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb', line 90



def num_waiting
  synchronize do
    @num_waiting
  end
end


  








  

    #poll(timeout = nil)  
  



  

    

Remove the head of the queue.



If timeout is not given, remove and return the head the queue if the number of available elements is strictly greater than the number of threads currently waiting (that is, don't jump ahead in line).  Otherwise, return nil.



If timeout is given, block if it there is no element available, waiting up to timeout seconds for an element to become available.



Raises:




becomes available after timeout seconds,


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb', line 132



def poll(timeout = nil)
  synchronize do
    if timeout
      no_wait_poll || wait_poll(timeout)
    else
      no_wait_poll
    end
  end
end