* Introduction of Happy Eyeballs Version 2 (RFC8305) in TCPSocket.new This is an implementation of Happy Eyeballs version 2 (RFC 8305) in `TCPSocket.new`. See https://.com/ruby/ruby/pull/11653 1. Background Prior to this implementation, I implemented Happy Eyeballs Version 2 (HEv2) for `Socket.tcp` in https://.com/ruby/ruby/pull/9374. HEv2 is an algorithm defined in [RFC 8305](https://datatracker.ietf.org/doc/html/rfc8305), aimed at improving network connectivity. For more details on the specific cases that HEv2 helps, please refer to https://bugs.ruby-lang.org/issues/20108. 2. Proposal & Outcome This proposal implements the same HEv2 algorithm in `TCPSocket.new`. Since `TCPSocket.new` is used more widely than `Socket.tcp`, this change is expected to broaden the impact of HEv2's benefits. Like `Socket.tcp`, I have also added `fast_fallback` keyword argument to `TCPSocket.new`. This option is set to true by default, enabling the HEv2 functionality. However, users can explicitly set it to false to disable HEv2 and use the previous behavior of `TCPSocket.new`. It should be noted that HEv2 is enabled only in environments where pthreads are available. This specification follows the approach taken in https://bugs.ruby-lang.org/issues/19965 , where name resolution can be interrupted. (In environments where pthreads are not available, the `fast_fallback` option is ignored.) 3. Performance Below is the benchmark of 100 requests to `www.ruby-lang.org` with the fast_fallback option set to true and false, respectively. While there is a slight performance degradation when HEv2 is enabled, the degradation is smaller compared to that seen in `Socket.tcp`. ``` ~/s/build ❯❯❯ ../install/bin/ruby ../ruby/test.rb Rehearsal -------------------------------------------------------- fast_fallback: true 0.017588 0.097045 0.114633 ( 1.460664) fast_fallback: false 0.014033 0.078984 0.093017 ( 1.413951) ----------------------------------------------- total: 0.207650sec user system total real fast_fallback: true 0.020891 0.124054 0.144945 ( 1.473816) fast_fallback: false 0.018392 0.110852 0.129244 ( 1.466014) ``` * Update debug prints Co-authored-by: Nobuyoshi Nakada <[email protected]> * Remove debug prints * misc * Disable HEv2 in Win * Raise resolution error with hostname resolution * Fix to handle errors * Remove warnings * Errors that do not need to be handled * misc * Improve doc * Fix bug on cancellation * Avoid EAI_ADDRFAMILY for resolving IPv6 * Follow upstream * misc * Refactor connection_attempt_fds management - Introduced allocate_connection_attempt_fds and reallocate_connection_attempt_fds for improved memory allocation of connection_attempt_fds - Added remove_connection_attempt_fd to resize connection_attempt_fds dynamically. - Simplified the in_progress_fds function to only check the size of connection_attempt_fds. * Rename do_pthread_create to raddrinfo_pthread_create to avoid conflicting --------- Co-authored-by: Nobuyoshi Nakada <[email protected]>