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 89
def initialize(lock = Monitor.new)
  @lock = lock
  @cond = @lock.new_cond
  @num_waiting = 0
  @queue = []
end

Public Instance Methods

add(element) Show source

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 112
def add(element)
  synchronize do
    @queue.push element
    @cond.signal
  end
end

Add element to the queue. Never blocks.

any_waiting?() Show source

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 97
def any_waiting?
  synchronize do
    @num_waiting > 0
  end
end

Test if any threads are currently waiting on the queue.

clear() Show source

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 127
def clear
  synchronize do
    @queue.clear
  end
end

Remove all elements from the queue.

delete(element) Show source

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 120
def delete(element)
  synchronize do
    @queue.delete(element)
  end
end

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

num_waiting() Show source

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 105
def num_waiting
  synchronize do
    @num_waiting
  end
end

Returns the number of threads currently waiting on this queue.

poll(timeout = nil) Show source

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 147
def poll(timeout = nil)
  synchronize { internal_poll(timeout) }
end

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 there is no element available, waiting up to timeout seconds for an element to become available.

Raises:

ActiveRecord::ConnectionTimeoutError if timeout is given and no element

becomes available within timeout seconds,