Does this mean that actix-web does not use actix (the actor system library) anymore? If so, is there any cause of concern regarding the maintenance and state of actix going forward? I think it's a very important library and would hate to see it abandoned. If anything, it needs more love, particularly regarding documentation.
I'm also interested in any alternatives for implementing an actor-based application in Rust, if any.
That is correct: the actor library is no longer used by default, although it can be imported and used in one's own server. The best part about using Rust is that it has shown to have a very good shelf life when a project reaches maintenance mode -- see the iron web framework as an example.
If the actix library suits your needs, why look elsewhere? Develop expertise and maintain it. If another actor project exists, the same risk of continuity applies.
The actix library is good, but as I mentioned the documentation is pretty lacking. Also it's changing very fast and the little info you can find on how to achieve certain things on e.g. reddit or StackOverflow is mostly obsolete now. Those are the only reasons why I'd be interested in seeing alternatives (if any exist, which is doubtful).
How can you be at the same time concerned by the fact “it's changing very fast” and having “concern regarding the maintenance and state of actix going forward” ?
Now that Actix isn't used in Actix-web anymore, I would expect two alternatives: it either continues to be developed at a fast pace (with frequent breaking changes) or it will settle it in current state, due to the lack of interest from its main author (with possible maintenance concerns, but with no more breaking changes). But I don't see how both could happen at the same time…
I don't have concerns regarding it changing very fast―it's often good for a novel library in a language (and an actors library for Rust qualifies as that) to iterate on the public APIs and experiment a bit to make the library better. I was just saying that to explain my grievances with the docs. Good experience for users is usually either a very well documented library which may then change quickly, or a not-that-well-documented library that has a stable interface so third-party info on how to use it does not get out of date quickly. Both of those together can create trouble. It did for me―Actix was so far the former, which is not ideal, but the latter would also be a pity if said stabilization happened because of abandonment, not out of convergence on a 1.0-worthy API.
I'm also interested in any alternatives for implementing an actor-based application in Rust, if any.