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

Inherits:
Object
  • Object
show all
Defined in:
lib/active_record/connection_adapters/abstract/connection_pool.rb

Overview

Threadsafe, fair, LIFO queue. Meant to be used by ConnectionPool with which it shares a Monitor.

Direct Known Subclasses

ConnectionLeasingQueue

Instance Method Summary collapse

Constructor Details

#initialize(lock = Monitor.new) ⇒ Queue

Returns a new instance of Queue.


86
87
88
89
90
91
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 86

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

Instance Method Details

#add(element) ⇒ Object

Add element to the queue. Never blocks.


109
110
111
112
113
114
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 109

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

#any_waiting?Boolean

Test if any threads are currently waiting on the queue.

Returns:

  • (Boolean)

94
95
96
97
98
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 94

def any_waiting?
  synchronize do
    @num_waiting > 0
  end
end

#clearObject

Remove all elements from the queue.


124
125
126
127
128
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 124

def clear
  synchronize do
    @queue.clear
  end
end

#delete(element) ⇒ Object

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


117
118
119
120
121
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 117

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

#num_waitingObject

Returns the number of threads currently waiting on this queue.


102
103
104
105
106
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 102

def num_waiting
  synchronize do
    @num_waiting
  end
end

#poll(timeout = nil) ⇒ Object

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,


144
145
146
# File 'lib/active_record/connection_adapters/abstract/connection_pool.rb', line 144

def poll(timeout = nil)
  synchronize { internal_poll(timeout) }
end