Elevator Project for TTK4145 Real Time Programming at NTNU

• Random Unique IDs for every order:
  • Makes it possible to differentiate a new order from the one that was completed a minute ago
• Peer-to-peer:
  • Every node may assign an order to any node
  • Every node stores all orders for all nodes
  • Every node regularly broadcasts all the orders for all nodes it believes are active
    • If a node receives an active order it knows is completed, it broadcasts the completed order so the other nodes may clear it
    • This ensures that the elevators quickly converge to a common belief state, even through restarts and disconnects/reconnects
  • Any node may clear a hall order if it has been finished, regardless of if it was the intended executor
• Order Delegation
  • The nodes regularly broadcast their states
  • The node that receives a button push delegates the order to the best recipent, given the stored states of the other nodes
• Redundancy
  • If an order is for any reason not completed within the deadline (40 seconds), every node redelegates the order to a new node
    • Remember that all the equivalent orders are cleared if one is completed

• OrderProcessor:
  • Keeps track of all orders in all nodes
  • Updates it's OrderRepository with incoming orders from other nodes
    • Sends all the active orders to the Controller if changes are made
  • Creates and broadcasts orders from button pushes if no equivalent orders exist
  • Clears all equivalent orders when arriving at a floor, broadcasts the completed orders to the other nodes
  • Regularly rebroadcasts all active orders
  • Regularly provides Watchdog with all the active orders, s.t. it may redelegate the ones not completed within the deadline
• Controller:
  • Interfaces with ElevatorServer, executes the active orders that belong to the node. Heavily based on elev_algo from the ProjectResources repository
  • Controls the motor, lights, door, and receives updates of new floors
  • Informs OrderProcessor when a button is pushed or a floor is stopped at, does not make decisions to create/complete orders itself
  • Informs Delegator when the state has changed
• Delegator:
  • Delegates new orders provided by OrderProcessor
  • Orders are delegated to the node with the lowest Cost
  • Redelegates orders to a new recipent if provided by Watchdog
• Watchdog:
  • Checks that active orders provided by OrderProcessor are completed within the deadline
    • Sends orders to Delegator to be redelegated if they are too old

• elevator:
  • Definitions of orders, elevator state, as well as types for buttons, motor directions etc.

• Network-go
  • Used for broadcasting and receiving elevator state and orders between nodes.
• driver-go
  • Used for interfacing with the ElevatorServer or Simulator