Introducing Kameo-persistence

[cwahn]

Hello, I am happy to introduce kameo-persistence, a persistence add-on for Kameo.

Motivation

For production-level application, it is necessary to remember some data and configuration on persistent storage, so that it could provide continuous user experience.

Of course this could be done in many other way, but I found it is quite repetitive and tedious task to do.

Solution

The solution I figured out is that make PersistentActor trait and assign unique "persistence key" (which is file URL at the moment) to instance, and let user could save "snapshot" at discretion.

The "Snapshot" type is something

• implements Serialize, Deserialize to be saved and restored.
• implements 'From<&Self: Actor> and Into<Self::Args> to capture snapshot from Actor and respawn Actor with Args.

By default it could be derivable with minimal manual implementation.
However for some manager-like actors holding dynamically created actor, I find useful to make Args type following the Actor type, but substituting ActorRef as URL so that sub actor could be spawned by on_start method.

Currently it suppose "persistence key" indicate directory-like path, not file-path, so that it could save it's intrinsic data, in "index file", while providing sub directory to conceptually owned sub actors so that they could save captures at their own phase. But this could be changed in future.

Todo

• Currently only URL pointing local file system works, but supporting HTTP(s), Ws(s), AWS S3 etc. like custom storage is in mind.
• Moreover, currently only supports URL as key, but custom key type works with custom storage could be implemented.

Note

Since this is very early draft, their would be plenty of issue.
Please feel free to leave comment so that it could serve your needs.