Class: Vli::Util::Busy

Inherits:
Object
  • Object
show all
Defined in:
lib/vli/util/busy.rb

Overview

Utility class which allows blocks of code to be marked as “busy” with a specified interrupt handler. During busy areas of code, it is often undesirable for SIGINTs to immediately kill the application. This class is a helper to cleanly register callbacks to handle this situation.

Constant Summary collapse

@@registered = 
[]
@@mutex = 
Mutex.new

Class Method Summary collapse

Class Method Details

.busy(sig_callback) ⇒ Object

Mark a given block of code as a “busy” block of code, which will register a SIGINT handler for the duration of the block. When a SIGINT occurs, the ‘sig_callback` proc will be called. It is up to the callback to behave properly and exit the application.



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# File 'lib/vli/util/busy.rb', line 17

def busy(sig_callback)
  register(sig_callback)
  yield
ensure
  unregister(sig_callback)
end

.fire_callbacks ⇒ Object

Fires all the registered callbacks.



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# File 'lib/vli/util/busy.rb', line 48

def fire_callbacks
  registered.reverse.each { |r| r.call }
end

.register(sig_callback) ⇒ Object

Registers a SIGINT handler. This typically is called from busy. Callbacks are only registered once, so calling this multiple times with the same callback has no consequence.



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# File 'lib/vli/util/busy.rb', line 27

def register(sig_callback)
  @@mutex.synchronize do
    registered << sig_callback
    registered.uniq!

    # Register the handler if this is our first callback.
    Signal.trap("INT") { fire_callbacks } if registered.length == 1
  end
end

.registered ⇒ Object

Helper method to get access to the class variable. This is mostly exposed for tests. This shouldn’t be mucked with directly, since it’s structure may change at any time.



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# File 'lib/vli/util/busy.rb', line 55

def registered; @@registered; end

.unregister(sig_callback) ⇒ Object

Unregisters a SIGINT handler.



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# File 'lib/vli/util/busy.rb', line 38

def unregister(sig_callback)
  @@mutex.synchronize do
    registered.delete(sig_callback)

    # Remove the signal trap if no more registered callbacks exist
    Signal.trap("INT", "DEFAULT") if registered.empty?
  end
end