Announcements for API changes

[kanpov]

Thread with announcement of major API breaking changes, to warn users before updating.

[kanpov]

Runtime abstraction and removal of FsBackend trait now allow interoperability between fctools and different async runtimes. Currently, both Tokio and the async-*/Smol stack are supported with the corresponding features. The community can add their own runtimes such as monoio or glommio if needed.

Available in: fctools 0.6.0-alpha.2

[kanpov]

The entire path-related system of all layers from VMM arguments up to the extensions has been reworked. Instead of inner paths, outer paths and such, a resource system has been introduced that divides resources associated with a VMM into three types:

• Moved, like a kernel image that is moved to be used by the VMM
• Created, like a log file that is created by fctools to be used by the VMM
• Produced, like a snapshot created by the VMM to be used by fctools

Even though this may seem more complicated, the introduction of this system has led to a major reduction of confusion and magic when it comes to paths in fctools, and has also reduced the footprint of the VM layer significantly by around 300-400 LOC that were dedicated to the complex inner-outer path former solution.

The builders for VM models were also removed in favor of standard pub structs.

Available (API not finalized) in: fctools 0.6.0-alpha.3, major breaking changes

[kanpov]

Note: while the improvements in the 0.6 alphas are major, it is recommended for current users of the library to continue using the stable 0.5 release to avoid much of the fallout of these transformative changes.

[kanpov]

Runtime-related traits now accept &self instead of being referred to without an instance of themselves to simplify inner-runtime state (like an async_executor::Executor<'static> for a smol-based runtime to get rid of static variable usage and related hacks in previous 0.6 alphas).

The order of components (i.e. Vm and VmmProcess prepare and new definitions) has been changed (omitting generics for the sake of brevity):

1. VmmExecutor
2. Arc<ProcessSpawner>
3. Runtime
4. VmmOwnershipModel
5. Arc<VmmInstallation>
6. VmConfiguration (only for Vms, of course)

The VmmExecutor trait has been simplified and modified in a breaking way, with a VmmExecutorContext<S: ProcessSpawner, R: Runtime> now encapsulating shared data for prepare + invoke + cleanup implementations. Concrete executors have been adjusted accordingly.

Various other small breaking changes have been made to lots of other places to accommodate for the fact that passing a <R: Runtime> generic is no longer enough, so a runtime: R or a runtime: &R argument has been added to dozens of functions.

Neat feature bonus: smol-hyper dependency has been removed in smol runtime, and support for async_executor::StaticExecutor has been added (according to the docs of async_executor, it has better performance than Arc<async_executor::Executor<'static>>).

Available in: fctools 0.6.0-alpha.6

[kanpov]

The resource system has been reworked, with everything no longer being piled up in the fctools::vmm::resource module. Instead of VmmResourceReferences, a VmmResourceManager trait is used that allows any type of iterators, and not just three Vecs (although a three-vec impl is provided in SimpleVmmResourceManager).

As a result of this:

• VmConfiguration implements VmmResourceManager
• VmmProcess is now parametrized additionally by a VmmResourceManager, resulting in a VmmProcess<E, S, R, RM> definition
• Vm doesn't have the RM generic as it always uses VmConfiguration

Available in: fctools 0.6.0-beta.1

[kanpov]

For anyone looking forward to a stable fctools 0.6, the release is greatly complicated by the third iteration of the VMM resource system and the associated rewrites/refactors (ETA: end of February or March). To anyone relying on fctools for stable projects, I suggest staying at 0.5 for the time being.