Articles Tagged: Akka

In previous articles we’ve talked about how we can implement a simple game using actors, and how we can use Akka’s remoting functions to build actor networks, so it’s time we put the pieces together and create a multiplayer game.

The game we’ll implement is called pişti or bastra, a card game that can be played with 2 to 4 people, and is pretty popular among people of all ages due to its simplicity.

At the start, each player is dealt 4 cards, and 4 other cards are placed in the middle of the table (also called the board), with one of them open. To ensure fairness, any jacks that are dealt on the board stack is randomly replaced with another from the deck so the players can get them later. On each turn, a player plays a card from their hand and places it on the board. If the card that is played is a jack, or if it matches the one on top of the board stack, the player collects the board (also called fishing) and earns points. If not, the card is left on the stack and the turn passes over to the next player. If the player runs out of cards they’re dealt 4 more, and the game lasts until all cards are played out. Once they are, whoever has the highest score wins the game.

In the previous article we’ve implemented a standalone guessing game, but actors are built for much more complex problems such as concurrent communication over a network. A turn-based multiplayer game such as a card or tile game is the perfect example for that use case, and that’s what we’d like to achieve eventually. But first, we need to figure out how to allow actors to communicate with each other over a networking layer, and possibly with a high enough level of abstraction so that we can model our business rules without having to think about any low-level stuff.

Thankfully, Akka does this abstraction so well that the whole process is almost entirely transparent. Let’s see how!

Now that the basics of the actor model is out of the way (thanks to the previous article), it’s time to make something with it! We’ll begin by creating an Akka project from scratch, and then move on to implementing a number guessing game based on actors, which will give us an easy start in modeling actor-based systems.

The rule of the game is quite simple; it’ll pick a random integer between 1 and 100, and user will try to guess it. Each time the user provides a guess, the game with reply with a message that tells the player whether or not they matched. All interaction will be through the console, so no unnecessary complication there.

Note: I won’t go into any details about the model nor Akka’s implementation of it, so if you’re ever in need of assistance, feel free to use the previous article as a reference.

By the time I took the Principles of Reactive Programming course on Coursera last spring, I was already a fan of Scala and concurrent programming, so it was no big surprise that I fell in love with the actor model the moment I heard about it during the course. I’ve been wanting to write about it ever since, but have only recently had the time to actually do it.

Let this be the first in a series of articles where I explore the actor model; what it is, how it works, where it can help, and how some of its use-cases may be implemented. I’ll first describe what the actor model is and how Akka implements it, then move on to simple examples like hot-or-cold games, and finally end up in client/server applications such as multiplayer card or tile games.

Disclaimer: This post assumes that you’re at least somewhat familiar with Scala.