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# frozen_string_literal: true
module Gitlab
# DEPRECATED. Use Gitlab::BackgroundTask for new code instead.
class Daemon
# Options:
# - recreate: We usually only allow a single instance per process to exist;
# this can be overridden with this switch, so that existing
# instances are stopped and recreated.
def self.initialize_instance(*args, recreate: false, **options)
if @instance
if recreate
@instance.stop
else
raise "#{name} singleton instance already initialized"
end
end
@instance = new(*args, **options)
Kernel.at_exit(&@instance.method(:stop))
@instance
end
def self.instance(...)
@instance ||= initialize_instance(...)
end
attr_reader :thread
def thread?
!thread.nil?
end
# Possible options:
# - synchronous [Boolean] if true, turns `start` into a blocking call
def initialize(**options)
@synchronous = options[:synchronous]
@mutex = Mutex.new
end
def enabled?
true
end
def thread_name
self.class.name.demodulize.underscore
end
def start
return unless enabled?
@mutex.synchronize do
break thread if thread?
if start_working
@thread = Thread.new do
Thread.current.name = thread_name
run_thread
end
@thread.join if @synchronous
@thread
end
end
end
def stop
@mutex.synchronize do
break unless thread?
stop_working
if thread
thread.wakeup if thread.alive?
begin
thread.join unless Thread.current == thread
rescue Exception # rubocop:disable Lint/RescueException
end
@thread = nil
end
end
end
private
# Executed in lock context before starting thread
# Needs to return success
def start_working
true
end
# Executed in separate thread
def run_thread
raise NotImplementedError
end
# Executed in lock context
def stop_working
# no-ops
end
end
end
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