Crashes!? We don't need no steenkin crashes
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README.md

Bandicoot

"I get knocked down, but I get up again. You're never gonna keep me down" -- Chumbawumba

Wouldn't video games suck without levels and save points? I can't even tell you the number of times I've been playing Pokemon, forgetting to save regularly, only to get in a trainer battle right when my mom calls me down to dinner. I was angry for the rest of the day thinking about how all that effort getting the Magikarp enough XP to evolve was wasted in that one flick of the power switch.

I feel similarly about my long running, data intensive tasks in Ruby. If I'm loading in a file with 200,000 records, some jackass has probably put a Windows-1252 character in record 195,095 or so. Restarting this process from the beginning would throw me into a rage.

Bandicoot lets you set save points from which future computation can resume. Have a boss battle with some complicated data 5 hours into a process? No problem! Bandicoot will let you try and fix the bugs and start again.

Warning

Bandicoot is a work in progress. Bandicoot is not currently thread (or Fiber) safe. I'm working on a way to make it work while maintaining decent semantics, but it is not there yet. It may destroy your computer and force you to lightly blow on your cartridges.

Usage

Basic usage involves setting Bandicoot up and defining save_points

Bandicoot.start do
  5.times do |i|
    the_meaning_of_life = 0
    the_meaning_of_life += Bandicoot.save_point(["outer", i]) do
      result = 0
      10.times do |j|
        result += Bandicoot.save_point(["inner", j]) do
          expensive_computation(j)
        end
      end
      result
    end
    the_meaning_of_life
  end
end

Save points have a key and take a block. The return value of Bandicoot.save_point is the return of the block. Save points can be nested arbitrarily and proper scoping will be maintained.

This example will always run all of the code, writing its progress out to a save file. If the program crashes, you can continue from where it left off by changing the first line to

Bandicoot.start(:continue => "path_to_save_file.save") do

It will then load in that file and whenever a save_point is encountered, it will check whether that save_point was completed. If it has been, the return value it gave last time will be returned and the block will not be run. If it has not been, it will be run and upon successful completion that save point will be recorded as well. In this manner, you can keep trying until you get it right.

Caveats and Considerations

  1. Bandicoot uses msgpack for serialization of keys and return values; therefore, keys and return values must be primitives where item == deserialize(serialize(item)). Practically, this means primitives and NO SYMBOLS. Arbitrarily nested arrays/hashes, numbers, and strings will work fine.

  2. The whole point of Bandicoot is to skip over already run blocks, so obviously any side effects in that block are not guaranteed to occur. Oftentimes this is fine and desired (e.g. inserting a row into a database), but if later code depends on side effects from earlier code, you may have a bad day.

  3. Your code could fail at any point in the save point block. Bandicoot will rerun the entire failing block, a bit of idempotence would probably be a good idea.

License

(MIT License)

Copyright (C) 2012 Ben Hughes, NabeWise Media

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.