class ActiveRecord::ConnectionAdapters::ConnectionPool::Queue

Parent:: Object

Threadsafe, fair, FIFO queue. Meant to be used by 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.

Public Class Methods

new(lock = Monitor.new) Show source

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 75
def initialize(lock = Monitor.new)
  @lock = lock
  @cond = @lock.new_cond
  @num_waiting = 0
  @queue = []
end

Public Instance Methods

add(element) Show source

Add element to the queue. Never blocks.

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 98
def add(element)
  synchronize do
    @queue.push element
    @cond.signal
  end
end

any_waiting?() Show source

Test if any threads are currently waiting on the queue.

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 83
def any_waiting?
  synchronize do
    @num_waiting > 0
  end
end

clear() Show source

Remove all elements from the queue.

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 113
def clear
  synchronize do
    @queue.clear
  end
end

delete(element) Show source

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

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 106
def delete(element)
  synchronize do
    @queue.delete(element)
  end
end

num_waiting() Show source

Returns the number of threads currently waiting on this queue.

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 91
def num_waiting
  synchronize do
    @num_waiting
  end
end

poll(timeout = nil) Show source

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:

ConnectionTimeoutError if timeout is given and no element

becomes available after timeout seconds,

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 133
def poll(timeout = nil)
  synchronize do
    if timeout
      no_wait_poll || wait_poll(timeout)
    else
      no_wait_poll
    end
  end
end