The client would receive the result of a computation by receiving a message. On the other hand, if there is a request-reply message exchange in an Actor system, both the request and the reply will be separate messages. In contrast, in an Actor system all communication is via asynchronous messages and there is no inherent requirement for multiple concurrent threads of execution.Īctive Objects use a mechanism such as futures to return results. So there may be a mixture of synchronous and asynchronous execution. In an OO system, not all objects are required to be Active Objects. Internally, the Active Object converts client requests into asynchronous operations, enqueues the operations, and executes them on a private worker thread using object-specific dispatcher logic. It provides clients with a synchronous call interface where all results are resolved asynchronously (e.g.
![actix stop actor actix stop actor](https://i.ytimg.com/vi/XjkB_O_rRgc/maxresdefault.jpg)
Here's how I see it:Īn Active Object is essentially an OO encapsulation of a worker thread. These allow us to design and implement distributed algorithms which would be hard to implement using traditional OOP methods.īased on the description in your Wikipedia link there is a relationship for sure - but I don't see a strong connection. It is fundamentally decentralized, locality is enforced and at-most-once message delivery is assumed. The Actor model is a good blueprint for our designs. With our modern systems design constraints, especially given distributed systems, we need to revisit those early decisions. This also explains the mismatch between remote systems calls (SOAP, REST, etc.) and the internal language. Method dispatch systems were later added, but could be considered a kludge. Locality was dropped (due to singletons) and the distributed model was not maintained.
![actix stop actor actix stop actor](https://user-images.githubusercontent.com/27893/58935105-fd8d7700-879e-11e9-8e09-2334eef8aee1.png)
#Actix stop actor full#
However, on the object oriented model track, due to practical reasons, its definition descended into a single-thread dispatch system with full message delivery guarantees. Both the actor model as defined by Carl Hewitt and the early object computational models as they are defined by Alan Kay (Smalltalk) originated during the same period and are based on similar philosophies of computation. Your question is interesting from the perspective that the actor model could be seen as the precursor to modern object oriented programming. You can test this in the playground by returning the if-expr directly instead of binding it to `result`. This happens when the if-expr is being returned directly and thus must have the same type as the function's return type, or it's being assigned to the binding and the binding has been previously inferred to have (or explicitly has) Box type. You don't need to coerce if the compiler can infer that the whole if-expr must be of Box type. (This auto-coercion also applies to other situations where the type of an expression must match the previous one's, such as with a slice literal where the first element dictates the types of the rest.) The compiler will auto-coerce the other one. You'll need to coerce the first expression to Box. Then by default, the type of the first Box will be concrete Box rather than Box, which is why you'll get a type error that Box != Box Or I just don't know what I'm doing, which is very possible.Īsync/await would be a huge improvement, but can't be used at the moment, even though the current version of Actix uses std::future's. Is a big pain requiring two layers of future::Either. Even if you box the returned Future, you end up having to use futures::Either a bunch and when you mess it up you get tons of confusing errors filled with the huge inferred types. Right now it's a huge pain to have more than one return value in an Actor Handler, the functions that handle actor messages.
![actix stop actor actix stop actor](https://gill.net.in/images/rust-lang-ar21.png)
My main pain point with it is the use of futures. I like it a lot and think the actor model is good fit for applications that don't fit well into a request lifecycle. I'm using both Actix and Actix web for a personal project. And I think websockets still require actors? Originally "Actix web" depended on Actix the actor library, but no longer. This is Actix the actor model library, not "Actix web" the web framework that's usually discussed.