GC Hacks for Ruby

A plugin for Rails which allows one to obtain heap dumps from a running rails app for example. It should work for mongrel and passenger hosted apps.

Author

Stefan Kaes <[email protected]>

Usage

Obtain the processid of a rails process, then invoke one of the following commands:

  • start_gc_trace pid # turns on gc tracing in the given process

  • stop_gc_trace pid # stop gc tracing

  • dump_heap pid # dump current heap to “#tmp_dir/heap.#Process.pid.#@heap_dump_count.dump”

Prerequisites

You won't have much fun with this code unless you use a patched ruby which supports dumping heap information, compiled with GC_DEBUG enabled.

I recommend my patched version of ruby 1.8.7, which you can get as follows:

git clone git://github.com/skaes/matzruby.git
cd matzruby
git checkout ruby187pl202patched
autoconf
./configure --enable-gcdebug --prefix=/usr/local/ruby187pl202
make
sudo make install
sudo make install-doc

Installation

Place it in vendor/plugins, as usual.

Acknowledgments

Development of this plugin was sponsored by Xing (www.xing.com)

TODO

  • I think this code should be a gem.

  • move railsbench analyze_heap_dump command into the gem.