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interrupt_handler.rb
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91 lines (81 loc) · 2.38 KB
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# frozen_string_literal: true
require 'singleton'
# Provides a handler for interrupt signals (SIGINT), allowing the application to
# finish what it's currently working on.
class InterruptHandler
include Singleton
attr_accessor :isolate_signals, :signal_received, :reenable_on_interrupt
# Initialize safe interrupt signal handling.
def initialize
self.isolate_signals = false
self.signal_received = false
self.reenable_on_interrupt = false
Signal.trap('INT') do
if isolate_signals
self.signal_received = true
else
if reenable_on_interrupt
self.reenable_on_interrupt = false
self.isolate_signals = true
end
raise Interrupt # Allow interrupt to propagate to code
end
end
end
class << self
# Provide a way to allow a single Ctrl-C interrupt to happen and atomically
# re-enable interrupt protections once that interrupt is propagated.
#
# This prevents a race condition where code like the following:
#
# begin
# InterruptHandler.disable!
# ... do stuff ...
# rescue Interrupt
# ... handle it ...
# ensure
# InterruptHandler.enable!
# end
#
# ...could have the `enable!` call to the interrupt handler not called in
# the event another interrupt was received in between the interrupt being
# handled and the `ensure` block being entered.
#
# Thus you should always write:
#
# begin
# InterruptHandler.disable_until_finished_or_interrupted do
# ... do stuff ...
# end
# rescue Interrupt
# ... handle it ...
# rescue
# ... handle any other exceptions ...
# end
def disable_until_finished_or_interrupted
instance.reenable_on_interrupt = true
instance.isolate_signals = false
yield
ensure
instance.isolate_signals = true
end
# Disable interrupt isolation.
def disable!
instance.isolate_signals = false
end
# Enable interrupt isolation.
def enable!
instance.isolate_signals = true
end
# Enable interrupt isolation while executing the provided block.
#
# @yield block to execute with interrupt isolation
def isolate_from_interrupts
instance.signal_received = false
instance.isolate_signals = true
result = yield
instance.isolate_signals = false
result
end
end
end