Class: Pgtk::Pool::IterableQueue

Inherits:
Object
  • Object
show all
Defined in:
lib/pgtk/pool/iterable_queue.rb

Overview

Thread-safe queue implementation that supports iteration. Unlike Ruby’s Queue class, this implementation allows safe iteration over all elements while maintaining thread safety for concurrent access.

This class is used internally by Pool to store database connections and provide the ability to iterate over them for inspection purposes.

The queue is bounded by size. When an item is taken out, it remains in the internal array but is marked as “taken”. When returned, it’s placed back in its original slot and marked as available.

Author

Yegor Bugayenko (yegor256@gmail.com)

Copyright

Copyright © 2019-2026 Yegor Bugayenko

License

MIT

Instance Method Summary collapse

Constructor Details

#initialize(size, timeout) ⇒ IterableQueue

Returns a new instance of IterableQueue.



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# File 'lib/pgtk/pool/iterable_queue.rb', line 26

def initialize(size, timeout)
  @size = size
  @timeout = timeout
  @items = []
  @taken = []
  @free = []
  @mutex = Mutex.new
  @condition = ConditionVariable.new
end

Instance Method Details

#map ⇒ Object 



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# File 'lib/pgtk/pool/iterable_queue.rb', line 78

def map(&)
  @mutex.synchronize do
    @items.map(&)
  end
end

#pop ⇒ Object 



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# File 'lib/pgtk/pool/iterable_queue.rb', line 56

def pop
  @mutex.synchronize do
    deadline = Process.clock_gettime(Process::CLOCK_MONOTONIC) + @timeout
    while @free.empty?
      remaining = deadline - Process.clock_gettime(Process::CLOCK_MONOTONIC)
      if remaining <= 0
        raise(Pgtk::Pool::Busy, "No free connection appeared in the pool after #{@timeout}s of waiting")
      end
      @condition.wait(@mutex, remaining)
    end
    index = @free.shift
    @taken[index] = true
    @items[index]
  end
end

#push(item) ⇒ Object 



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# File 'lib/pgtk/pool/iterable_queue.rb', line 36

def push(item)
  @mutex.synchronize do
    if @items.size < @size
      @items << item
      @taken << false
      @free << (@items.size - 1)
    else
      index = @items.index(item)
      if index.nil?
        index = @taken.index(true)
        raise(StandardError, 'No taken slot found') if index.nil?
        @items[index] = item
      end
      @taken[index] = false
      @free << index
    end
    @condition.signal
  end
end

#size ⇒ Object 



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# File 'lib/pgtk/pool/iterable_queue.rb', line 72

def size
  @mutex.synchronize do
    @items.size
  end
end