This is really awkward. The problem was found after moving some scripts that worked fine on one server to another server with rubygems recently updated. The script normally spawns several processes that are DRb Servers, but it failed silently. After some testing I found that with every other thing being equal (Ruby 1.8.6 patchlevel 111 and win32-process 0.5.3 on both machines) the script crashed with gem 1.2.0 and not with 0.9.4.
The script iterates calling Process.fork with a code block that creates the new DRb server. The DRb object is loaded via require at the begining of the script. I’m posting here a reduced example for clarity.
puts "iniciando"
require 'rubygems'
require 'drb'
puts 'loading pingpong'
require 'pingpong'
puts 'loaded pingpong'
puts 'loading process '
require 'win32/process'
puts 'loaded process'
def start_server(port)
uri="druby://0.0.0.0:#{port}"
trap("INT"){puts("Interrupted"); DRb.thread.exit}
DRb.start_service(uri,PingPong.new)
puts("Listening #{uri}")
DRb.thread.join
end
puts "here #{ARGV.inspect}"
2.times{|port| puts("Sending #{port}");Process.fork{start_server(5850+port)}}
puts "out"
The PingPong class is defined in the following script. Note the $KCODE declaration since it turned out to be the problem:
$KCODE = 'UTF-8'
class PingPong
def ping
"pong"
end
end
In the current implementation of win32_process, Process.fork works by creating a new Windows process calling Ruby with the same script and passing an argument indicating which child is creating. This is very important as indicated in the documentation since one would expect that each child’s execution started at the code block passed to the fork.
The process failed like this with gem 1.2.0 (but worked perfectly on gem 0.9.4:)
C:\>test_fork_simple.rb iniciando loading pingpong loaded pingpong loading process loaded process here [] Sending 0 Sending 1 out
After some hours debugging I found that the problem arised when the $KCODE assigment is done on the child processes; if the assigment is deleted the processes are created correctly:
C:\>test_fork_simple.rb iniciando loading pingpong loaded pingpong loading process loaded process here [] Sending 0 Sending 1 out iniciando iniciando loading pingpong loading pingpong loaded pingpong loading process loaded pingpong loading process loaded process here ["child#0"] Sending 0 loaded process here ["child#1"] Sending 0 Sending 1 Listening druby://0.0.0.0:5850 Listening druby://0.0.0.0:5851
But in the real programs the line can’t be left out since it’s critical. Oddly enough, the workaround consisted on switching the ‘require’ statments for the child class and win32/process:
#Crashes silently: require 'pingpong' require 'win32/process' #Works! require 'win32/process' require 'pingpong'
It’s also very strange that, when the script fails, the child processes are not even created (as you can see on the first output, the “iniciando” message is never sent). I’ll post an update if I found what’s happening here.