Combining the Strengths or Erlang and Ruby
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The document discusses the architecture and implementation of a game server combining Erlang and Ruby for a Wooga game, focusing on stateful processes for user sessions and effective state management. It outlines the benefits of using a functional approach in Erlang alongside an object-oriented modeling in Ruby, and describes communication between the two languages using technologies like ZeroMQ. The document emphasizes performance optimization and efficient game state access through a specialized serialization format.
![Example Game Ac4on in Ruby
URL
game_action '/:actor/fruit_tree/self/shake',
:affects => [:fruit_trees, :user] do |response|
x, y = params[:x], params[:y]
fruit_trees[x, y].shake affected parts of
end
the game state
• DSL-‐like defini4on of game ac4on
• skinny as controllers should be 8-‐)](https://image.slidesharecdn.com/2012-02-29-erloungeberlin-120301045211-phpapp01/85/Combining-the-Strengths-or-Erlang-and-Ruby-8-320.jpg)
![Looking back at the Game Ac4on
game_action '/:actor/fruit_tree/self/shake',
:affects => [:fruit_trees, :user] do |response|
x, y = params[:x], params[:y]
fruit_trees[x, y].shake affected parts of
end
the game state
• Ruby knows the mapping of game ac4ons to affected state parts
• pushes the mapping on startup & makes it available on request](https://image.slidesharecdn.com/2012-02-29-erloungeberlin-120301045211-phpapp01/85/Combining-the-Strengths-or-Erlang-and-Ruby-15-320.jpg)
Combining the Strengths or Erlang and Ruby
- 1. COMBINING THE STRENGTHS OF ERLANG AND RUBY erlounge Berlin February 2012 – Mar4n Rehfeld
- 2. Game Server for Upcoming Wooga Game What is a game server? • provide HTTP API to actual game („client“) • validate API calls against current state & game logic • API calls will modify the game state • make game state persistent
- 3. Game Server for Upcoming Wooga Game It will be a stateful game server • one process per ac4ve user gaming session • the process holds the current state and is the only one that can modify it (strong encapsula:on) • the process handles all API calls for the given user one a=er the other (concurrency control through actor model) • the process loads the game state from storage and writes it back periodically and on process termina:on (:meout = user stopped playing)
- 4. Game Server for Upcoming Wooga Game Details on the basic idea: Awesome presenta4on on the Magic Land game server by @knu4n & @hungryblank hZp://www.slideshare.net/wooga/from-‐0-‐to-‐1000000-‐daily-‐users-‐with-‐erlang
- 5. Our Goals • Get most of the benefits from wooga’s pure-‐erlang game server (Magic Land) • especially func:onal approach for game state encapsula:on and transforma:on + concurrency control • But: Keep Object-‐Oriented approach for modelling the game logic
- 6. Expected OO-‐Benefits • Rapid development • concise & expressive syntax • leverage exis4ng know how • but: keep the OO part stateless and side-‐effect free to avoid the usual traps & pidalls
- 7. Target Architecture Authority for: Load Balancer "What app server is responsible for current session?" App Server Node App Server Node App Server Node Erlang VM Erlang VM Erlang VM ... Ruby Ruby Ruby Ruby Ruby Ruby Ruby Ruby Ruby ... ... ... Worker Worker Worker Worker Worker Worker Worker Worker Worker Shared Storage for game state snapshots and for storing cold game sessions
- 8. Example Game Ac4on in Ruby URL game_action '/:actor/fruit_tree/self/shake', :affects => [:fruit_trees, :user] do |response| x, y = params[:x], params[:y] fruit_trees[x, y].shake affected parts of end the game state • DSL-‐like defini4on of game ac4on • skinny as controllers should be 8-‐)
- 9. Example Model in Ruby Inheritance class FruitTree < Tree property :last_shake_time, :type => Integer, :default => 0 DSL-‐like defini4on property :collectable_fruit_count, :type => Integer, :default => 0 of persistent state def shake raise Error::Validation, "FruitTree at (#{x}, #{y}) has no fruit" unless carries_fruit? session.user.xp += 1 session.user.energy -= 1 self.last_shake_time = game_time self.collectable_fruit_count = config.fruit_count end # ... end • easily unit testable • minimal amount of code
- 10. erlang talking to Ruby Some op4ons • erlectricity hZps://github.com/mojombo/erlectricity: Can talk erlang binary protocol to Ruby processes through erlang ports • ernie hZps://github.com/mojombo/ernie: Remote func4on call using the BERT-‐RPC protocol to either Ruby or na4ve erlang processes • ZeroMQ <hZp://www.zeromq.org/>: awesome brokerless queue transport layer, connects 30+ languages
- 11. ZeroMQ Pro Con • loose coupling of erlang and • yet another layer Ruby through queues • easily deploy new Ruby code without touching erlang • allows flexible transports, even accross machines
- 12. Connec4ng the Dots • use Mongrel2 hZp://mongrel2.org/ protocol & ZeroMQ setup • erlang: emongrel2 hZps://github.com/hungryblank/emongrel2 • Ruby • rack-‐mongrel2 fork hEps://github.com/khiltd/khi-‐rack-‐mongrel2 • rack protocol hEp://rack.rubyforge.org • Sinatra hEp://www.sinatrarb.com/ ➡ essen4ally we are speaking HTTP over ZeroMQ and can hook up any Rack-‐based Ruby web framework
- 13. Setup Overview server worker session worker sender Push/Pull Queue 1:n worker session worker ... receiver Pub/Sub Queue m:n ... session worker
- 14. How does the game state look like? • Has many parts, each part has a name (e.g. fruit_trees) and some content • this is a performance op:miza:on, so that we don't need to send the complete state back and forth for every call • erlang does not care about the content (binary data) • actually the content contains serialized objects (e.g. a MapObjectCollection containing FruitTree members) • erlang does need to know, what game ac4on needs what state parts
- 15. Looking back at the Game Ac4on game_action '/:actor/fruit_tree/self/shake', :affects => [:fruit_trees, :user] do |response| x, y = params[:x], params[:y] fruit_trees[x, y].shake affected parts of end the game state • Ruby knows the mapping of game ac4ons to affected state parts • pushes the mapping on startup & makes it available on request
- 16. Aside: Efficient Game State Access • considered different serializa4on formats (e.g. JSON, MessagePack) • especially for large collec4ons of objects we wanted to avoid parsing everything to extract a single object • chose TNetstrings hZp://tnetstrings.org/ as a serializa4on format (length prefix helps searching/lazy parsing) • built a lazy parser/encoder for it in C for speed :-‐) hZps://github.com/wooga/lazy_tnetstring
- 17. Q & A Mar4n Rehfeld @klickmich