Mower-akka
A simple implementation of the mower scenario using akka and scala
I need help!
The solution branch could be useful.
Track
TODO 1
Complete MowerActor. Once done, MowerActorSpecs should pass.
TODO 1.1
Complete MowerActor's companion object props() method. The goal is to create a Propos instance with the arguments of the actor class's constructor.
See doc on props
What are props ?
Props instance is a memoization of the your business actor class constructor arguments.
What is the use of props ?
Once a Props instance is created, the actor system remembers the arguments needed to build your business actor class.
Thus, it is able to trash it an restart it as many times as the actor's lifecycle need it: the same original arguments are passed to your actor constructor each time it is called.
You will see when thereafter that you never create yourself an instance of your actor class; instead, you tell the actor system its props, and then the actor system create it.
TODO 1.2
You need to have this code compiling. See comments from 1.2.* todos in MowerActor.ready method.
Goal: pattern match the received message to choose what to do.
TODO 2
We want the SurfaceActor to listen for message using ready method; because this is the starting state.
See the "become" doc to see how to change the method that is receiving messages.
Why become ?
become word implies a state change. In he actor model, you can think of the state machine matrix as an UML's state/transition diagram:
- some message makes your actor to transition to a new state
- each state is able to receive a specific set of messages
Thus become will be useful elsewhere in the code...
TODO 3: SurfaceActor's ready state
Fill in the missing code to
- iterate through surface config keys. The keys are Mowers, values are the list of commands Mower as key must execute.
- for each Mower key, start a MowerActor and send an
ExecuteCommandsmessage with the list of commands - then switch to working state
TODO 4: SurfaceActor's working state
In working state, SurfaceActor will receive request from MowerActors. It goal is to answer to MowerActor if it can go forward (the requested position on surface is free) or not (the requested position is occupied by another Mower).
This is where collisions are managed.
Finding if next position is free or not is given. You just need to implement
- what to do if the result is "free"
- what do to if the result is "occupied"
- what to do if the result is occupied and we tried it to much time
See help in TODO 4.* comments
TODO 5: Let's try it
See the doc about creating an actor with props to create your actor system, your SurfaceActor and start it.
Ensure that log levels are properly configured to see the system live.