Seed Providers

Cloacina ships a small library of canonical providers — one per primitive kind. They are real, runnable building blocks and double as the reference implementations for authoring each kind.

Two providers have been promoted to the providers/ directory and are published to crates.io as part of the provider release waves: cloacina-provider-fs (WASM task suite) and cloacina-provider-kafka (native stream-accumulator suite; not listed below — see Author a Provider for its native tier). The remaining seed reference implementations (sensor, extract, quorum) still live under examples/constructor-contract/ and are not yet published.

Provider	Location	Kind	Member(s)	Config	What it does
`cloacina-provider-fs`	`providers/` (crates.io)	task	`read_file`, `write_file`	`path`	Reads/writes a file through the sandbox. `write_file` takes its `contents` as a required runtime param from the upstream context.
`cloacina-provider-sensor`	`examples/constructor-contract/`	trigger	`file_present`	`path`	The classic file sensor: fires when the path exists inside the sandbox, skips otherwise. Without an `fs` grant the path is invisible — the sensor fails closed by never firing.
`cloacina-provider-extract`	`examples/constructor-contract/`	accumulator	`extract`	`field`	Projects the configured field out of each event into the boundary; events without it buffer. The everyday map/filter from an event stream into boundaries.
`cloacina-provider-quorum`	`examples/constructor-contract/`	reactor	`quorum`	`required`	Fires the graph when at least `required` boundaries are held — N-of-M firing criteria. `required = 1` is “fire on anything”.

Example — the fs task member in a workflow:

constructor!(
    id = "reader",
    from = "cloacina-provider-fs@0.1.0",
    constructor = "read_file",
    config = { path = "/etc/hostname" },
    grants = { fs = ["ro:/etc"] },
);

Consumption surface per kind

task — constructor!(...) in a #[workflow] (Rust) or cloaca.constructor(...) (Python).
reactor — #[reactor(from = "...", constructor = "...", config(...))] replaces the reactor’s firing criteria with the WASM member’s evaluate.
trigger / accumulator — loaded through the embedded runtime registration API (load_constructor lands the member in the matching Runtime registry); declarative macro surfaces for these kinds are a follow-on.

A note on state

The authoring model rebuilds the member instance from its bound config per call, so seed accumulators are stateless transforms. Cross-event state (count/time windows) needs runtime-held state and is a planned follow-on — if you need windowing today, author an ordinary Rust accumulator (e.g. #[state_accumulator] for a bounded rolling window, or #[batch_accumulator] for buffered flushes).