Re: [PATCH proxmox 01/20] router: introduce shared state

["Lukas Wagner" <l.wagner@proxmox.com>]

On Mon Aug 17, 2026 at 2:57 PM CEST, Lukas Wagner wrote:
> API handlers often need access to long-lived application data such as
> configuration, caches or client handles. So far the only way to get
> there is a global static, which hides the actual dependencies of a
> handler and makes testing awkward.
>
> Add a type-keyed registry that a server fills once during startup,
> together with an accessor on RpcEnvironment so that handlers can reach
> it. The State<T> newtype wraps values that come from the registry,
> which allows telling them apart from regular API parameters.
>

Since the question came up off-list:

The reason why this is a type-keyed map is that we can inject multiple
types that can later be retrieved by using the State<T> macro. This
allows, for example, having API handlers in crates that require their
own context type to be set up. For instance, in proxmox-notify, one
requires proxmox_notify::Context to be implemented and set up.
For passing that along in API handlers, there could be a 

struct NotifyContext {
    inner: Box<dyn proxmox_notify::Context>
}

and then in the API handlers defined in proxmox_notify, the context
could then be retrieved as

fn add_sendmail_endpoint(context: State<NotifyContext>, ...) {}

This the outcome of a suggestion from Robert from the RFC of this
series:

https://lore.proxmox.com/pdm-devel/20260129134418.307552-1-l.wagner@proxmox.com/T/#t

In general, this is pretty much identical to how actix-web handles it:

https://actix.rs/docs/application/#state

Under the hood they also use a type-keyed map with `dyn Any` as a value
type.