rm "at_exit"

[ruseel]

at_exit seems to leak memory.

checked with below script
(copied from SamSaffron's
rubyjs/therubyracer#336)

require 'objspace'
require 'memory_profiler'
require 'fluent-logger'

def rss
 `ps -eo pid,rss | grep #{Process.pid} | awk '{print $2}'`.to_i
end

MemoryProfiler::Helpers.full_gc
puts "rss: #{rss} live objects #{GC.stat[:heap_live_slots]}"

20.times do
  500.times { |i|
    Fluent::Logger::FluentLogger.new.post("tag", {"a"=>1})
  }

  MemoryProfiler::Helpers.full_gc
  puts "rss: #{rss} live objects #{GC.stat[:heap_live_slots]}"
end

before this patch

rss: 19528 live objects 38181
rss: 20836 live objects 46999
rss: 21108 live objects 54998
rss: 21948 live objects 62998
rss: 22992 live objects 70998
rss: 24192 live objects 78998
rss: 25248 live objects 86998
rss: 26324 live objects 94998
rss: 27432 live objects 102998
rss: 28556 live objects 110998
...
...

after

rss: 19840 live objects 38181
rss: 20988 live objects 38998
rss: 21048 live objects 38997
rss: 21056 live objects 38997
rss: 21116 live objects 38997
rss: 21116 live objects 38997
rss: 21116 live objects 38997
rss: 21116 live objects 38997
rss: 21116 live objects 38997
rss: 21116 live objects 38997
rss: 21116 live objects 38997
rss: 21116 live objects 38997
...
...

[repeatedly]

It seems at_exit's slot isn't GCed in one process.
Does this become a problem?
From our experience, user doesn't create lots of FluentLogger instance in one process.

Anyway, if we merge this PR, we should announce the users because this change breaks existing FluentLogger behaviour.

[ruseel]

Does this become a problem?
From our experience, user doesn't create lots of FluentLogger instance in one process.

I did create a lots of FluentLogger instance. and now I see that is definitely not good as you said.