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Ruby module for monitoring GC
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GcMonitor is Ruby library for monitoring GC.


Add this line to your application's Gemfile:

gem 'gc_monitor'

And then execute:

$ bundle

Or install it yourself as:

$ gem install gc_monitor


If you want to monitor the specific class, then include GcMonitor into the class.

require 'gc_monitor'

class Foo
  attr_accessor :dummy

class Foo
  include GcMonitor

Foo.release_hook('puts "i am released."')  # This is option hook, for debug.

15.times do
  o =
  o.dummy = 'x' * 100 * 1024 * 1024  # For GC.
  sleep 0.5

GcMonitor.list.each{|rec| p rec}  # Array of the remaining objects (not garbage collected).

# You can filter the objects by :time keyword.
GcMonitor.list(:time => 8).each{|rec| p rec}  # Only older than 8 sec.

Then "i am released." will be printed when some Foo instances are collected. At the last code, the remaining objects will be dumped.

i am released.
i am released.
["Foo__fdbef6946", {:time=>Sun Aug 09 00:11:49 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8f52", {:time=>Sun Aug 09 00:11:50 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8dfe", {:time=>Sun Aug 09 00:11:55 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8c28", {:time=>Sun Aug 09 00:11:57 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8912", {:time=>Sun Aug 09 00:11:59 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef87c8", {:time=>Sun Aug 09 00:12:00 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef84ee", {:time=>Sun Aug 09 00:12:02 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8386", {:time=>Sun Aug 09 00:12:04 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8110", {:time=>Sun Aug 09 00:12:05 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef7ea4", {:time=>Sun Aug 09 00:12:07 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8f3e", {:time=>Sun Aug 09 00:12:09 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8f34", {:time=>Sun Aug 09 00:12:10 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
["Foo__fdbef8e76", {:time=>Sun Aug 09 00:12:12 +0900 2009, :caller=>["gc_monitor.rb:136:in `new'", "gc_monitor.rb:136", "gc_monitor.rb:135:in `times'", "gc_monitor.rb:135"]}]
i am released.
i am released.

You can monitor almost all of classes. Instead of "include GcMonitor" in the class definition, call GcMonitor.include_in_subclasses. But some classes are not supported, Time (sorry...) and implemented classes in ruby such as String and so on.

GcMonitor.include_in_subclasses(Object)  # If you monitor IO and the sub classes, set the argument IO.

Finally, there is TCP/IP interface.

GcMonitor.tcp_server('', 4321)

And using TCP/IP client, you can monitor the realtime information by 'list' command.

$ telnet localhost 4321
Trying ::1...
Connected to localhost.
Escape character is '^]'.
now: Sun Aug 09 00:48:59 +0900 2009
["Rational__fdbe7752e", {:time=>Sun Aug 09 00:48:56 +0900 2009, :caller=>["/usr/lib/ruby/1.8/rational.rb:94:in `new'", "/usr/lib/ruby/1.8/rational.rb:94:in `new!'", "/usr/lib/ruby/1.8/rational.rb:337:in `coerce'", "/usr/lib/ruby/1.8/date.rb:503:in `-'", "/usr/lib/ruby/1.8/date.rb:503:in `jd_to_ajd'", "/usr/lib/ruby/1.8/date.rb:754:in `new'", "gc_monitor.rb:155", "gc_monitor.rb:154:in `times'", "gc_monitor.rb:154"]}]
list 8   <== Only the remaining objects older than 8 sec ago.
quit     <== Command for quit TCP/IP interface.


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
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