From: ben@...
Date: 2020-07-31T18:46:27+00:00
Subject: [ruby-core:99423] [Ruby master Bug#15773] Net::HTTP doesn't try next IP address in case of timeout
Issue #15773 has been updated by benlangfeld (Ben Langfeld).
naruse (Yui NARUSE) wrote in #note-1:
> In general resolving DNS is done by libc (getaddrinfo) and Ruby just uses their result.
> Therefore it is not a bug and won't be a small feature.
RFC3484 (https://www.ietf.org/rfc/rfc3484.txt) very clearly states:
```
Well-behaved applications SHOULD iterate through the list of
addresses returned from getaddrinfo() until they find a working
address.
```
That Ruby does not do this should be considered a bug, and I would ask that you please re-open this ticket on that basis. Ruby is in contravention of the RFC and the documentation of `getaddrinfo(3)`. This is not a missing feature; Ruby is broken. Note that I am not asking that anyone fix this; I will prepare a fix. All I ask is that this ticket be acknowledged as valid and not rejected based on misunderstanding it.
----------------------------------------
Bug #15773: Net::HTTP doesn't try next IP address in case of timeout
https://bugs.ruby-lang.org/issues/15773#change-86876
* Author: nicolasnoble (Nicolas Noble)
* Status: Rejected
* Priority: Normal
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
This example requires to have a working IPv6 address. Since IPv6 is used in first priority, I am using it to demonstrate the problem, but it exists with plain IPv4, which will be more round-robin-style, so less deterministic to show a reproduction case. I have made two URLs that have both IPv4 and IPv6 addresses: http://ipv6.grumpycoder.net/ and http://bad-ipv6.grumpycoder.net/ - both URLs should work in an IPv6-enabled web browser, as well as curl or wget for instance. The difference is that the bad-ipv6 subdomain doesn't have an IPv6 that will actually connect. Therefore, browsers, curl and wget will fallback to using the IPv4 when the initial IPv6 connection attempt failed:
```
$ wget -T1 http://bad-ipv6.grumpycoder.net -O - # demonstrating using wget because its output is more clear than curl's verbose
--2019-04-16 15:56:52-- http://bad-ipv6.grumpycoder.net/
Resolving bad-ipv6.grumpycoder.net (bad-ipv6.grumpycoder.net)... 2001:bc8:3690:200::2, 62.210.214.144
Connecting to bad-ipv6.grumpycoder.net (bad-ipv6.grumpycoder.net)|2001:bc8:3690:200::2|:80... failed: Connection timed out.
Connecting to bad-ipv6.grumpycoder.net (bad-ipv6.grumpycoder.net)|62.210.214.144|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 45 [text/html]
Saving to: ���STDOUT���
- 0%[ ] 0 --.-KB/s It works!
- 100%[=====================================================================>] 45 --.-KB/s in 0s
2019-04-16 15:56:53 (6.55 MB/s) - written to stdout [45/45]
```
However, in Ruby, using Net::HTTP (or OpenURI), that's not going to be the case:
```
$ ruby bad-ipv6.rb
http://ipv6.grumpycoder.net
It works!
http://bad-ipv6.grumpycoder.net
Net::OpenTimeout: execution expired
```
Contents of my test file:
```ruby
require 'open-uri'
['ipv6', 'bad-ipv6'].each do |s|
url = 'http://%s.grumpycoder.net' %[s]
puts url
begin
puts open(url).read
rescue StandardError => e
puts "#{e.class}: #{e.message}"
next
end
end
```
The proper behavior should be to retry the next IP address and exhaust all of the IPs in the DNS resolution results before throwing out an error.
--
https://bugs.ruby-lang.org/
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