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Plain tower

[dependencies]
dynamic-config-tower = "<version>"

For every tower stack that is not axum: tonic, plain hyper, a framework of your own. SnapshotLayer wraps any Service<http::Request<B>>; the snapshot goes into the request's extensions, and reading it back out is yours:

use dynamic_config_tower::{sections, Snapshot, SnapshotLayer};
use tower::{service_fn, Layer, Service, ServiceExt};

let service = service_fn(|request: http::Request<Body>| async move {
    let snapshot = request.extensions().get::<Snapshot>().expect("the layer ran");
    let server = snapshot.require::<ServerConfig>()?;   // errors name the fix
    // …
});

let mut wired = SnapshotLayer::new(sections![ServerConfig]).layer(service);

Snapshot::require is the read that distinguishes the two mistakes: NotListed (add it to sections![...]) and NotLoaded (call init() before serving). get is the Option form for code with its own opinion about absence.

With tonic, attach the layer through Server::builder().layer(...); a gRPC method reads the snapshot from the request extensions exactly as above. The Long-lived Connections page applies to streaming RPCs verbatim.