NAME

dike

SYNOPSIS

a simple memory leak detector for ruby with preconfigured rails hooks.

INSTALL

gem install dike

URIS

http://www.codeforpeople.com/lib/ruby/
http://rubyforge.org/projects/codeforpeople/

DESCRIPTION

the concept behind dike.rb is simple: class Object is extended in order that
the location of each object's creation is tracked.  a summarizer command is
given to walk ObjectSpace using each object's class and the location if it's
creation to detect memory leaks.  not all leaks can be detected and some that
are may not really be leaks, but dike provided a simple way to see the
hotspots in your code that may potentially be leaking.

EXAMPLES

### PURE RUBY

 ## just dumping sequential snapshots to stderr

  # cfp:~ > cat sample/a.rb
      require 'dike'

      Leaks = Array.new

      loop do
        Leaks << String.new('leak' * 1024)
        Dike.finger
        sleep 1
      end

  # cfp:~ > ruby sample/a.rb | less
      ...

      - class: String
        count: 2 
        trace:
        - sample/a.rb:6
        - sample/a.rb:5:in `loop'
        - sample/a.rb:5

      ...

      - class: String
        count: 10 
        trace:
        - sample/a.rb:6
        - sample/a.rb:5:in `loop'
        - sample/a.rb:5

      ...

      - class: String
        count: 42 
        trace:
        - sample/a.rb:6
        - sample/a.rb:5:in `loop'
        - sample/a.rb:5

 ## dumping sequential snapshots using Dike.logfactory and then using the 'dike'
    command line tool to do comparisons of the dumped snapshots

  # cfp:~ > cat sample/b.rb
      require 'dike'

      Leaks = Array.new

      class Leak
        def initialize
          @leak = 42.chr * (2 ** 20)
        end
      end

      Dike.logfactory './log/'

      Dike.finger

      3.times{ Leaks << Leak.new  }

      Dike.finger

      2.times{ Leaks << Leak.new  }

      Dike.finger

  # cfp:~ > ruby sample/b.rb

  # cfp:~ > ls log/
      0       1       2

  # cfp:~ > dike log/
      --- 
      - class: Leak
        count: 3
        trace: 
        - sample/b.rb:15
        - sample/b.rb:15:in `times'
        - sample/b.rb:15
      - class: Leak
        count: 2
        trace: 
        - sample/b.rb:19
        - sample/b.rb:19:in `times'
        - sample/b.rb:19

  # cfp:~ > dike log/0 log/1
      --- 
      - class: Leak
        count: 3
        trace: 
        - sample/b.rb:15
        - sample/b.rb:15:in `times'
        - sample/b.rb:15

  # cfp:~ > dike log/1 log/2
      --- 
      - class: Leak
        count: 2
        trace: 
        - sample/b.rb:19
        - sample/b.rb:19:in `times'
        - sample/b.rb:19

### RAILS

  # cfp:~ > cat ./config/environment.rb
    ...
    require 'dike'
    Dike.on :rails

  # cfp:~ > ./script/server

  # cfp:~ > curl --silent http://localhost:3000 >/dev/null

  # cfp:~ > cat ./log/dike/0
    ---
    - class: String
      count: 90769
      trace: []
    - class: Array
      count: 18931
      trace: []
    - class: Class
      count: 2
      trace:
      - votelink.com/public/../config/../lib/widgets.rb:222:in `class_factory'
      - votelink.com/public/../config/../lib/widgets.rb:220:in `each'
      - votelink.com/public/../config/../lib/widgets.rb:220:in `class_factory'
      - votelink.com/public/../config/../lib/widgets.rb:248:in `Widget'
      - votelink.com/public/../config/../lib/widgets/page/base.rb:1
      - votelink.com/public/../config/../lib/widgets.rb:31:in `require'
      - votelink.com/public/../config/../lib/widgets.rb:31:in `load'
      - votelink.com/public/../config/../lib/widgets.rb:16:in `for_controller'
      - votelink.com/public/../config/../lib/widgets.rb:243:in `widget'
      - votelink.com/public/../config/../app/controllers/application.rb:150
    ...

  # cfp:~ > curl --silent http://localhost:3000 >/dev/null

  # cfp:~ > cat ./log/dike/1
    ---
    - class: String
      count: 100769
      trace: []
    - class: Array
      count: 19931
      trace: []
    - class: Class
      count: 5
      trace:
      - votelink.com/public/../config/../lib/widgets.rb:222:in `class_factory'
      - votelink.com/public/../config/../lib/widgets.rb:220:in `each'
      - votelink.com/public/../config/../lib/widgets.rb:220:in `class_factory'
      - votelink.com/public/../config/../lib/widgets.rb:248:in `Widget'
      - votelink.com/public/../config/../lib/widgets/page/base.rb:1
      - votelink.com/public/../config/../lib/widgets.rb:31:in `require'
      - votelink.com/public/../config/../lib/widgets.rb:31:in `load'
      - votelink.com/public/../config/../lib/widgets.rb:16:in `for_controller'
      - votelink.com/public/../config/../lib/widgets.rb:243:in `widget'
      - votelink.com/public/../config/../app/controllers/application.rb:150
    ...

  # cfp:~ > dike ./log/dike
    ...
    - class: Class
      count: 3
      trace:
      - votelink.com/public/../config/../lib/widgets.rb:222:in `class_factory'
      - votelink.com/public/../config/../lib/widgets.rb:220:in `each'
      - votelink.com/public/../config/../lib/widgets.rb:220:in `class_factory'
      - votelink.com/public/../config/../lib/widgets.rb:248:in `Widget'
      - votelink.com/public/../config/../lib/widgets/page/base.rb:1
      - votelink.com/public/../config/../lib/widgets.rb:31:in `require'
      - votelink.com/public/../config/../lib/widgets.rb:31:in `load'
      - votelink.com/public/../config/../lib/widgets.rb:16:in `for_controller'
      - votelink.com/public/../config/../lib/widgets.rb:243:in `widget'
      - votelink.com/public/../config/../app/controllers/application.rb:150
    ...

NOTES

* the 'Dike.finger' method dumps it's log in a format showing

  class : the class of object being leaked/allocated
  count : the number instances leaked from the trace location
  trace : the trace location of object creation

* loading into a rails environment causes snapshots of the above format to
  be dumped into RAILS_ROOT/log/dike/ after each request.  each snapshot is
  incrementally numbered 0, 1, ...

* the 'dike' command line tool can be used in two ways

    dike directory/with/logs/dike/

    dike old_dump new_dump

  if given a directory 'old_dump' and 'new_dump' are auto-calculated by
  scanning the directory.  in either case the tool dups a delta running old
  -->> new.  the delta shows only changes from old to new, so a line like

    - class: Proc
      count: 3 
      ...

  means that 3 Proc objects were created between the two dumps.  note that,
  when given a directory, the default old and new dumps are the oldest and
  newest dumps respectively, to get fine grained information sumarizing the
  changes between two requests give the files manually, for example

    dike ./log/dike/41 ./log/dike/42

* options that affect logging

  - Dike.filter pattern

      pattern must respond to '===' and each object in ObjectSpace will be
      compared against it.  for example

        Dile.filter Array

      would cause logging to restrict itself to Array, or sublcasses of
      Array

  - Dike.log io

      set the dike logging object.  the object should respond to 'puts'.

  - Dike.logfactory directory

      cause logging to occur into a new log for each call the 'Dike.finger'.
      the logs will be auto numbered 0, 1, ...

LIMITATIONS

not all object creation can be tracked. not all leaks are reported. some
reported leaks are not. dike shows you where in the source objects are being
created that cannot be reclaimed - these are not always leaks as this line

  class C; end

shows.  the class 'C' cannot be reclaimed and is not a leak.

AUTHOR

ara [dot] t [dot] howard [at] gmail [dot] com