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.

Stefan Kaes <skaes@railexpress.de>

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”

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

Place it in vendor/plugins, as usual.

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

• I think this code should be a gem.

• move railsbench analyze_heap_dump command into the gem.