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AV00 Transport

Inter-Service communication for AV00

Built on top of NetMQ

Info

Details can be found here in the project plan readme AV00 Primary Repo

Message Types

  • Event
    • Any event we want to share with other services.
  • EventReceipt
    • Allows tracking of event progress.

Services

  • Relay ** The Relay is a service that receives events and distributes them as necessary.

Prebuilt Client Examples

  • EventLogger
    • A special purpose client that is capable of sending a log event as well as writing it to the console.
  • TransportClient
    • A barebones client that can push (and push async) events to the relay. This client can also receive events on various topics.

Future Clients

  • TBD but I'm sure something will come up. Especially when we start working with sensor data.

Usage

Setting Up A Client

In order to send and receive events, we need to configure a basic transport client. You can extend the basic transport client to add more functionality such as a socket for receiving event receipts. Currently the constructor for the basic transport client is going to need three arguments: PushEventSocket, SubscribeEventSocket, TransportMessageFrameCount.

These arguments can be passed from ConfigurationManager.

TransportClient myTransportClient = new(ConfigurationManager.ConnectionStrings, ConfigurationManager.AppSettings);

We can pass these arguments using our IConfigurationService.

TransportClient myTransportClient = new(Configuration)

Or we can manually pass the arguments.

TransportClient myTransportClient = new(SubscriberEventSocket, PushEventSocket, TransportMessageFrameCount)

Using Events For Sharing Data With Other Services

The base object sent between services over ZeroMQ is an Event<T> (IEvent). Event is a simple carrier object capable of serializing and deserializing itself and an EventModel (IEventModel) it's carrying. You can see the documentation for EventModel here: AV00 Shared Repo

In order to create an Event<T> for transport we must first create some data in the form of an EventModel. Once we have some data, we simply pass it to the Event<T> constructor to get an Event.

MotorCommandEventModel myData = new("DriveService",  EnumMotorCommands.Move, MotorDirection.Forwards, 1024)

Event<MotorCommandEventModel> @event = new(myData)

Assuming we have a transport client, we can send this event.

myTransportClient.PushEvent(@event);

We can then receive the event.

myTransportClient.RegisterServiceEventCallback("DriveService", MyCallbackFunction);
myTransportClient.ProcessPendingEvents()