Class: ThreadLimiter

Inherits:
Object
  • Object
show all
Defined in:
lib/threadlimiter/threadlimiter.rb

Overview

Fork threads like Thread.fork, but limit the number of concurrently running threads.

ThreadLimiter isn’t a thread pool. Each fork really starts a new thread.

Instance Method Summary collapse

Constructor Details

#initialize(limit = -1)) ⇒ ThreadLimiter

Initialize the ThreadLimter. The optional parameter limit is the maximum number of concurrently running threads. Set limit to -1 or 0 to fork threads without limiting the number of concurrently running threads.



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# File 'lib/threadlimiter/threadlimiter.rb', line 11

def initialize(limit=-1)
  @limit	= limit	# The maximum number of concurrently running threads.
  @running	= 0	# The number of currently running threads.

  @mutex	= Mutex.new
  @cv		= ConditionVariable.new
end

Instance Method Details

#fork(*args, &block) ⇒ Object

Fork a thread. The given block is run within the thread. It behaves like Thread.fork(). In fact, it invokes Thread.fork() and returns its result. The list of arguments is passed to Thread.fork().



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# File 'lib/threadlimiter/threadlimiter.rb', line 25

def fork(*args, &block)
  if @limit <= 0
    Thread.fork(*args, &block)
  else
    @mutex.synchronize do
      while @running >= @limit
        @cv.wait(@mutex)
      end

      @running	+= 1
    end

    Thread.fork do
      begin
        res	= yield(*args)
      ensure
        @mutex.synchronize do
          @running	-= 1
        end

        @cv.signal	if @limit > 0
      end

      res
    end
  end
end