Feature #17528: Make Addrinfo.getaddrinfo fall back to Timeout.timeout for :resolv_timeout

• Status: Open
• Assignee: -
• Target version: -

[mohamedhafez (Mohamed Hafez)]

Currently, Addrinfo.getaddrinfo ignores the :resolv_timeout option if we are on a system without getaddrinfo_a. It would be great if instead it would fall back to using Timeout.timeout.

That way, we could get rid of a lot of the usage of Timeout.timeout for systems that do have getaddrinfo_a. For example, for Net::HTTP#connect we could easily then do something like this: https://github.com/ruby/ruby/compare/master...mohamedhafez:patch-3?diff=split.

The motivation for this is that the usage of Timeout.timeout is inherently unsafe, and it would be great to stop using it where we can (see https://www.mikeperham.com/2015/05/08/timeout-rubys-most-dangerous-api/ and http://blog.headius.com/2008/02/ruby-threadraise-threadkill-timeoutrb.html)

[akr (Akira Tanaka)]

I think Timeout.timeout doesn't work for Addrinfo.getaddrinfo
because Timeout.timeout cannot interrupt getaddrinfo function in C.

[mohamedhafez (Mohamed Hafez)]

According to https://bugs.ruby-lang.org/issues/12435, the only reason we are using Timeout.timeout in Net::HTTP#connect instead of using nonblocking io and IO.select is so that we can place a timeout on the getaddrinfo function, @normalperson (Eric Wong) can you clarify here?

[akr (Akira Tanaka)]

How to test:

% vi /etc/resolv.conf      # specify non-existing nameserver
% time ./ruby -rtimeout -rsocket -e 'Timeout.timeout(2) { Addrinfo.getaddrinfo("www.ruby-lang.org",nil) }'
-e:1:in `getaddrinfo': execution expired (Timeout::Error)
	from -e:1:in `block in <main>'
	from /home/akr/o0/lib/ruby/3.1.0/timeout.rb:112:in `timeout'
	from -e:1:in `<main>'
./ruby -rtimeout -rsocket -e   0.14s user 0.00s system 0% cpu 20.136 total

This needs 20 second instead of 2 second.

[mohamedhafez (Mohamed Hafez)]

I was just doing a similar test actually, I think you're correct! I'll close this issue and re-submit a patch to Net::HTTP to replace Timeout::timeout there, since it's not doing anything for DNS lookups anyway. Thank you!

[hsbt (Hiroshi SHIBATA)]

• Related to Feature #17525: Implement Happy Eyeballs Version 2 (RFC8305) in Socket.tcp added