Using at_exit for graceful stop upon receiving a SIGINT in JRuby

[Adithya-copart]

This resolves #1675.
Sorry about the noise in that issue but you can find a sample app here demonstrating the problem.

The graceful_stop is not using the same thread as the at_exit blocks and is being run in the JVM signal handling thread in JRuby.

So, the thread.join here is joining @thread on the signal handler thread and I'm not sure if that is the intention.

This fix will execute graceful_stop within the at_exit block on the main thread.

Link: jruby/jruby#5437

[nateberkopec]

Needs a test. Probably just an adaptation/simplification of your reproduction app.

[Adithya-copart]

@nateberkopec I'm not sure how to come up with a working test.
I'm running into an issue after adding a test to test_integration.rb.

The problem is executing the following code in a irb session will block at Process.wait(server.pid) when running on master but not in this branch.

However, if I add the same code to a file and run it, the puma process is shutting down properly on both the branches. I'm not sure what to make out from this.

require 'open3'

server = IO.popen("rackup test/rackup/jruby-sigint.ru")

# Wait for bootup
true while server.gets !~ /Ctrl-C/

t1 = Time.now
Process.kill(:INT, server.pid)
Process.wait(server.pid)
p "Time elapsed: #{Time.now - t1}"

[Adithya-copart]

pid = spawn("rackup test/rackup/jruby-sigint.ru")

# Wait until bootup
sleep 6
t1 = Time.now
Process.kill(:INT, pid)
Process.wait(pid)
p "Time elapsed: #{Time.now - t1}"

This works inside a file, I'll see if I can integrate this into a test instead.
I might need to make sure the teardown works if the server fails to shutdown.

[Adithya-copart]

Faced jruby/jruby#1050 (comment) with an approach using Timeout.timeout and Process.wait.

So, I came-up with a test that fails on master and passes in this branch but it does use sleep.

[Adithya-copart]

@nateberkopec I opened jruby/jruby#5844 to understand #1868 (comment).

@headius investigated the issue and added jruby/jruby#5844 (comment).

This piece of code may not longer be needed in Puma. It was initially added in cli.rb via 1dbe28e a long time ago and was later moved to launcher.rb.

#1675 no longer happens when I remove this code. The puma server shutdown as expected.

puma/lib/puma/launcher.rb

Lines 408 to 413 in 9fb1228

	Signal.trap "SIGINT" do
	if Puma.jruby?
	@status = :exit
	graceful_stop
	exit
	end

[nateberkopec]

@Adithya-copart It looks like Evan added that code in response to this comment: #73 (comment)

What do you think? I guess Ctrl-C still shuts down the JVM right? Is that what you're seeing?

[Adithya-copart]

Yep, Ctrl+C is shutting down the JVM without that piece of code.

Tested on my Mac and a JRuby docker container.

[nateberkopec]

Does it remove the socket still, though? I guess it must if the tests are passing. Originally that's why this code was added, ctrl-c just blew up the JVM without properly removing the socket.

[nateberkopec]

@Adithya-copart maybe the test should check to make sure the socket is removed?

_{Sent with GitHawk}

[Adithya-copart]

Updated the test to check if the port is available after shutdown.
Let me know if this is not what you had in mind.

[nateberkopec]

Closing in favor of #1961