How can I check whether current script in Ruby is being closed?
Particularly, in case program is closing, I want to set @reconnect to false, not to allow web-socket reconnect any more. I tried Signal.trap("TERM"), but it doesn't seem to work.
@reconnect is an instance variable inside WebsocketClient class, i can't directly change it in my script outside class.
class WebsocketClient
def ws_closed(event)
$logger.warn "WS CLOSED"
Signal.trap("TERM") {
@stop = true
@reconnect = false
}
unless $reauth
if @stop
EM.stop
elsif @reconnect
$logger.warn "Reconnecting..."
EM.add_timer(@reconnect_after){ connect! }
end
end
end
end
at_exit {
$logger.fatal "Application terminated. Shutting down gracefully..."
# ...
# Do some exit work...
# ...
exit!
}
Output on CTRL-C
01-02-2018 12:00:54.59 WARN > WS CLOSED
01-02-2018 12:00:54.595 WARN > Reconnecting...
01-02-2018 12:00:54.596 FATAL > Application terminated. Shutting down gracefully..
See Below taken from my answer Here but seems more pertinent to your question than the one it is currently attached to:
Your best bet is probably a bit easier than signal trapping. The Kernel Module actually offers you an #at_exit method that will be executed just prior to the program actually exiting.
Usage: (from Kernel#at_exit Docs)
def do_at_exit(str1)
at_exit { print str1 }
end
at_exit { puts "cruel world" }
do_at_exit("goodbye ")
exit
"produces:"
goodbye cruel world
as you can see you can define multiple handlers which will be executed in reverse order when the program exits.
Since Kernel is included in Object you can handle Object specifics as well like
class People
at_exit {puts "The #{self.name} have left"}
end
exit
# The People have left
or even on instances
p = People.new
p.send(:at_exit, &->{puts "We are leaving"})
# We are leaving
# The People have left
Additionally for more specific Object based implementations you can take a look at ObjectSpace.define_finalizer.
example of usage:
class Person
def self.finalize(name)
proc {puts "Goodbye Cruel World -#{name}"}
end
def initialize(name)
@name = name
ObjectSpace.define_finalizer(self, self.class.finalize(@name))
end
end
Usage:
p = Person.new("engineersmnky")
exit
# Goodbye Cruel World -engineersmnky
This may not be specifically what you want as this will fire when an Object is garbage collected as well (not great for ephemeral objects) but if you have objects that should exist throughout the entire application this could still be used similar to an at_exit . Example
# requiring WeakRef to allow garbage collection
# See: https://ruby-doc.org/stdlib-2.3.3/libdoc/weakref/rdoc/WeakRef.html
require 'weakref' #
p1 = Person.new("Engineer")
p2 = Person.new("Engineer's Monkey")
p2 = WeakRef.new(p2)
GC.start # just for this example
# Goodbye Cruel World -Engineer's Monkey
#=> nil
p2
#=> WeakRef::RefError: Invalid Reference - probably recycled
exit
# Goodbye Cruel World -Engineer
As you can see the defined finalizer for p2 fired because the Person was gc'd but the program has not exited yet. p1's finalizer waited until exit to fire because it retained its reference throughout the application.