Initial implementation of actors

[danielgerlag]

Actor Runtime

To author an actor,

1. Create a struct with your custom actor methods and annotate your input and output types as serializable. The SDK will automatically deserialize the incoming parameters from JSON and then serialize your result back to JSON.

   #[derive(Serialize, Deserialize)]
   pub struct MyRequest {
       pub name: String,
   }
   
   #[derive(Serialize, Deserialize)]
   pub struct MyResponse {
       pub available: bool,
   }   
   
   impl MyActor {
       fn do_stuff(&mut self, data: MyRequest) -> Result<MyResponse, actor::ActorError> {        
           println!("doing stuff with {}", data.name);        
           Ok(MyResponse { 
               available: true 
           })
       }    
   }

2. Implement the Actor trait. This trait exposes the following methods:

   • on_activate - Called when an actor is activated on a host
   • on_deactivate - Called when an actor is deactivated on a host
   • on_reminder - Called when a reminder is recieved from the Dapr sidecar
   • on_timer - Called when a timer is recieved from the Dapr sidecar

   impl Actor for MyActor {
       
       async fn on_activate(&mut self) -> Result<(), ActorError> {
           println!("on_activate {}", self.id);
           Ok(())
       }
   
       fn on_deactivate(&mut self) -> Result<(), ActorError> {
           println!("on_deactivate");
           Ok(())
       }
   }

3. An actor host requires an Http server to recieve callbacks from the Dapr sidecar. The DaprHttpServer object implements this functionality and also encapsulates the actor runtime to service any hosted actors. Use the register_actor method to register an actor type to be serviced, this method takes an ActorTypeRegistration which specifies

   • The actor type name
   • A factory to construct a new instance of that actor type when one is required to be activated by the runtime. The parameters passed to the factory will be the actor type, actor ID, and a Dapr client for managing state, timers and reminders for the actor.
   • The methods that you would like to expose to external clients.

   let mut dapr_server = dapr::server::DaprHttpServer::new();
   
   dapr_server.register_actor(ActorTypeRegistration::new("MyActor", 
       |actor_type, id, client| Box::new(MyActor{
           actor_type, 
           id, 
           client
       }))
       .register_method("do_stuff", MyActor::do_stuff)
       .register_method("do_other_stuff", MyActor::do_other_stuff));
   
   dapr_server.start(None, None).await?;

[tqq1994516]

When will this PR be incorporated into the master, I am looking forward to the actor related functions

[danielgerlag]

Closing in favor of #99