socrates-rs

Dynamic Modules and Services for Rust

About

For crates that known they know nothing... :)

An experimental framework for dynamic modules in Rust. It is a work-in-progress, everything is bound to change.

Inspired by Java/OSGi but trying to fix past mistakes. Using using Rust patterns (RAII, variable lifetimes) to make usage smooth, minimize stale references, etc.

Status

Very very early, but core ideas seem to work pretty well. Built on Rust nightly.

In a nutshell:

• Dynamic modules are called Dynamod. You install them in a Container instance. When you start them, their Activator is called and can interact with the framework.
• You register a service by moving it to the framework, and get a ServiceRegistration in exchange.
• Others can get your service wrapped as Svc<dyn YourService>. It is similar to an Arc, but the framework acts as a 3rd party and does magic so that your services can have cycles.
• RAII everywhere: drop your ServiceRegistration to unregister your service, drop a Svc to drop use count.
• A service or the shared library holding its code is never dropped if someone still holds a reference.
  • And we can detect stale references/modules (called zombies).
  • It's fundamentally a collaborative model: you get asked nicely to let go of things that are unregistered.
• The component framework will make dynamics much easier to handle.

Examples

There's a very small demo in examples/.

Roadmap

• Basic container
• Dynamic services
• Small demo
• More tests!
• More documentation!
• More refactoring
• Lifecycle state, etc
• Configuration management (using JSON + serde on custom structs?)
• More service properties
  • service ranking/ordering supported
• Lazy/Factories and Prototype services
• Manifests for shared objects
• Stop requiring #[no_mangle], define a real interface for instantiation (activators, service components)
• Compatibility resolution and inspection at install
• Lazy loading of shared objects (by get_service)
• programmable, extensible Service Component Framework
  • dependency injection
  • (a better replacement than ServiceTrackers)
  • plugin any kind of events (not only service events & configuration)
  • should work also for any Rust application without dynamic loading.
• Declarative bindings for the component framework (using macros or derive)
• APIs for everything
  • Use it to build hot reload + watcher?
• More non-blocking stuff (integrate with futures-rs)
  • e.g event dispatch, activate / deactivate methods
  • reusable base services, e.g a tokio core event loop running on futures provided by services
• A blog post/series?

License

Apache Software License 2.0

Credits

Built on top of the libloading and query_interface crates. Thanks! Thanks to everyone helping on IRC, and especially mbrubeck & talchas :-)

(c) 2018 Simon Chemouil, Lambdacube SARL