Feature #17470: Introduce non-blocking `Timeout.timeout`

• Status: Closed
• Assignee: ioquatix (Samuel Williams)
• Target version: -

[ioquatix (Samuel Williams)]

In this bug report, user complained that Timeout.timeout does not work correctly with scheduler: https://github.com/socketry/async-io/issues/43

We should introduce non-blocking timeout.

I propose the following:

rb_fiber_scheduler_with_timeout(VALUE scheduler, VALUE timeout, VALUE block)

We can directly modify Timeout.timeout to invoke this hook.

[Eregon (Benoit Daloze)]

How would that work, what would be a sample implementation of the hook?
Timeout.timeout must be able to interrupt non-IO operations as well.

[ioquatix (Samuel Williams)]

Timeout.timeout must be able to interrupt non-IO operations as well.

Actually, that's not necessarily true, even for the current implementation, see getaddrinfo for example.

[jsc (Justin Collins)]

It appears that Timeout.timeout does not work when a Fiber scheduler is set, regardless of the implementation, even when Fibers are not explicitly in use.

Simple example using the sample scheduler:

require 'timeout'
require 'fiber'
require_relative 'scheduler'

scheduler = Scheduler.new
Fiber.set_scheduler scheduler

Timeout.timeout 1 do
  puts "hello"
end

This code will print "hello" then hang.

[Eregon (Benoit Daloze)]

ioquatix (Samuel Williams) wrote in #note-2:

Actually, that's not necessarily true, even for the current implementation, see getaddrinfo for example.

You're completely evading my question :p
Could you answer it please?

That's one of the very rare cases, maybe even the only case in core methods that cannot be interrupted by Thread#raise.

Is the idea to simply give up on interrupting anything that's not handled by the scheduler if there is a Fiber.scheduler, or something better?
That seems too incompatible to me.
I think a new API to interrupt only scheduler things might make more sense (related to #17363).

[Eregon (Benoit Daloze)]

• Related to Feature #17363: Timeouts added

[jeremyevans0 (Jeremy Evans)]

• Tracker changed from Bug to Feature
• Backport deleted (2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN)

[ioquatix (Samuel Williams)]

@Eregon (Benoit Daloze) without preemptive scheduling it won't be possible. There are other cases where the GVL is not released, e.g. the sqlite3 gem. In the case of the scheduler, Timeout.timeout is completely broken, so this is an improvement any way you cut it.

[ioquatix (Samuel Williams)]

@jsc (Justin Collins) I tried your example but it seems to work fine?

  MESSAGE = "Hello World"

  def test_timeout_on_main_fiber
    message = nil

    thread = Thread.new do
      scheduler = Scheduler.new
      Fiber.set_scheduler scheduler

      Timeout.timeout(1) do
        message = MESSAGE
      end
    end

    thread.join

    assert_equal MESSAGE, message
  end

[ioquatix (Samuel Williams)]

• Status changed from Open to Closed
• Assignee set to ioquatix (Samuel Williams)

Implemented in https://github.com/ruby/ruby/pull/4173.