Project Structure

Although the project structure can be arbitrary, it looks reasonable to provide some advices here:

• Use a separate crate for every actor group.
  • It speeds up a build time.
  • It helps to isolate code.
• Use separate crates for protocols, where messages are defined. Internal messages (timer ticks, inner group messages etc) are defined inside a group's crate.
• Actor crates shouldn't depend on each other. Instead, they should depend on protocol crates.
  • It helps to achieve loosely coupling.
• Prefer integration tests (tests/) over unit tests (mod tests). Unit tests are still fine for internal structures.
  • Integration tests use no implementation details and relies only on protocols.
• Store libraries (additional code potentially used by multiple actors) separately from actors' code. It's ok to depends on protocols in that code, but don't depend on actors. libs/ in the example below.
• Store different parts of a group in dedicated files, it siplifies navigation:
  • exec() and message handling in actor.rs.
  • An inner-group router in router.rs.
  • A group's config in config.rs.
• Store topology definitions separately from actors' code. Services can share actors. Also, it's a good place for additional files like systemd units and so on. services/ in the example below.

For instance:

actors/
    <actor_name_1>/
        src/
            mod.rs
            actor.rs
            config.rs
            router.rs
        tests/
            helpers.rs
            test_<name_1>.rs
            test_<name_2>.rs
        Cargo.toml
    <actor_name_2>/
protocol/
    src/
        lib.rs
    Cargo.toml
libs/
    <lib_name_1>/
    <lib_name_2>/
services/
    <service_name_1>/
    <service_name_2>/
Cargo.toml
Cargo.lock
rustfmt.toml