Traffic Lights Control system

Real-time traffic lights control system modelled using Akka Actors.

Technologies

Scala
Akka Actors - 2.5.x
Akka HTTP - 10.x
WebSockets
React.js + Redux

Build

Uses SBT to build backend components and Webpack to pack front-end assets.

npm install
npm run build
sbt test:compile

Test

sbt test

Run

sbt run

Http server runs default at http://localhost:8080/demo

REST API

GET /api/layouts/{systemId}

returns system layout as JSON

GET /api/lights/{systemId}

returns system status as JSON

GET /api/lights/{systemId}/{lightId}

returns light state as JSON

WS API

GET /ws/lights

live stream of all light state events

GET /ws/lights/{systemId}

live stream of light state events for systemId

GET /ws/lights/{systemId}/{lightId}

live stream of light state events for systemId_lightId

Model

Each traffic control component receives commands: ChangeToRedCommand, ChangeToGreenCommand and signal events: ChangedToRedEvent, ChangedToGreenEvent.

Each component also consumes, produces or passes TickEvents.

TrafficSystem: outermost component, wraps other component and sends TickEvents at intervals
Light: the most primitive component of traffic system control taking one of four states sequentially: RedLight, ChangingToGreenLight, GreenLight, ChangingToRedLight
Group: set of components amongst which all are changing to the same state in the same time (all becomes Red or all becomes Green)
Sequence: set of components amongst which only one can become Green at the same time, the rest have to become Red.
TimeOffset: proxy component delaying commands
Pulse: proxy component consuming TickEvents and sends ChangeToGreenCommands
Switch: proxy component consuming TickEvents and sends alternately ChangeToGreenCommand and ChangeToRedCommand

All statefull components reports StateChangeEvent to the event listener.

Demo traffic system definition:

Sequence("s1", SequenceStrategy.RoundRobin,
      Sequence("s2", SequenceStrategy.RoundRobin,
        Group(
          "g1",
          Light("l1", RedLight),
          Offset(
            500.millis,
            Light("l2", GreenLight)
          )
        ),
        Group(
          "g2",
          Light("l3", GreenLight),
          Offset(
            1.second,
            Light("l4", RedLight)
          )
        ),
        Group(
          "g3",
          Light("l5", GreenLight),
          Offset(
            1.second,
            Light("l6", RedLight)
          ),
          Sequence("s3", SequenceStrategy.RoundRobin,
            Light("l7", RedLight),
            Light("l8", RedLight),
            Light("l9", RedLight))
        )),
      Sequence("s12", SequenceStrategy.RoundRobin,
        Group(
          "g11",
          Offset(
            500.millis,
            Light("l12", GreenLight)
          ),
          Light("l11", RedLight)
        ),
        Group(
          "g12",
          Offset(
            1.second,
            Sequence("s14", SequenceStrategy.RoundRobin,
              Light("l14a", RedLight),
              Light("l14b", RedLight))
          ),
          Light("l13", GreenLight)
        ),
        Group(
          "g13",
          Light("l15", GreenLight),
          Light("l16", RedLight),
          Offset(
            1.second,
            Sequence("s13", SequenceStrategy.RoundRobin,
              Light("l17", RedLight),
              Light("l19", RedLight))
          )
        )))

arturopala/traffic-lights-control