Ruby Socket.gethostbyname random failures

output_alpine.txt

ruby:2.3.1-alpine

/ # ruby test.rb 
Failed after 10729 successes
SocketError
getaddrinfo: Try again
test.rb:8:in `gethostbyname'
test.rb:8:in `<main>'
/ # 
/ # ruby --version
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
/ # uname -a
Linux ruby-01 3.10.0-327.4.4.el7.x86_64 #1 SMP Tue Jan 5 16:07:00 UTC 2016 x86_64 Linux
/ # cat /etc/*release
3.4.4
NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.4.4
PRETTY_NAME="Alpine Linux v3.4"
HOME_URL="http://alpinelinux.org"
BUG_REPORT_URL="http://bugs.alpinelinux.org"
/ # 

output_slim.txt

ruby:2.3.1-slim

root@ruby-01:/# ruby test.rb 
^CExited after 34594 successes
root@ruby-01:/# 

root@ruby-01:/# ruby --version
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
root@ruby-01:/# uname -a
Linux ruby-01 3.10.0-327.4.4.el7.x86_64 #1 SMP Tue Jan 5 16:07:00 UTC 2016 x86_64 GNU/Linux
root@ruby-01:/# cat /etc/*release
PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"
ID=debian
HOME_URL="http://www.debian.org/"
SUPPORT_URL="http://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
root@ruby-01:/# 

test_dns.rb

#!/usr/bin/ruby
require 'resolv'

counter = 0

begin
  while true do
    begin
      Socket.gethostbyname('www.google.com')
      counter += 1
    rescue
      puts "Failed after #{counter} successes"
      puts $!.class
      puts $!.message
      puts $!.backtrace
      break
    end
  end
rescue SystemExit, Interrupt
  puts "Exited after #{counter} successes"
end

The crashing and slowness are two different issues. Based on the results so far

1. Alpine based images could cause getaddr crash in ruby, if we move away from alpine based image, we may be able to solve this issue.
2. Other type of ruby images have the same issue of slowness as python, or just simple curl. These facts point to the possible culprit of kubernetes issue.

Besides the ruby code, we can also use sh script

for i in $(seq 1 100); \
do \
curl -o /dev/null -s -w "DNS-Lookup [%{time_namelookup}] Time-Connect [%{time_connect}] Time-PreTransfer [%{time_pretransfer}] Time-StartTransfer [%{time_starttransfer}] Total-Time [%{time_total}]\n" https://www.google.com/ ; \
done
``` to test the name lookup time.