[ANN] dike-0.0.4.rb

ara.t.howard · January 9, 2008, 11:02pm

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.

HISTORY

0.0.4:

- under rare circumstances dike itself interacted strangely with

certain
classes and caused them to leak, HTTPOK was one such example.
this
release fixes that bug. thanks to Jan Kubr for providing a
great test
case that helped me fix this.

EXAMPLES

PURE RUBY

just dumping sequential snapshots to stderr, looking at a

specific class

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

    class Leak < ::String
    end

    Leaks = Array.new

    Dike.filter Leak

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


# cfp:~ > ruby sample/a.rb | less
    ---
    - class: Leak
      count: 2
      trace:
      - sample/a.rb:11
      - sample/a.rb:10:in `loop'
      - sample/a.rb:10
    ---
    - class: Leak
      count: 3
      trace:
      - sample/a.rb:11
      - sample/a.rb:10:in `loop'
      - sample/a.rb:10
    ---
    - class: Leak
      count: 4
      trace:
      - sample/a.rb:11
      - sample/a.rb:10:in `loop'
      - sample/a.rb:10
    ---
    - class: Leak
      count: 5
      trace:
      - sample/a.rb:11
      - sample/a.rb:10:in `loop'
      - sample/a.rb:10
    ---
    - class: Leak
      count: 6
      trace:
      - sample/a.rb:11
      - sample/a.rb:10:in `loop'
      - sample/a.rb:10

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 yet is not a leak.

AUTHOR

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

enjoy!