Struct SharedConfig 

pub struct SharedConfig<T> { /* private fields */ }

Available on crate features config-reload and config only.

Thread-safe shared configuration with version tracking and change notification.

Designed for hot-reload: components subscribe to config changes via the watch channel and react accordingly. The version counter provides a cheap way to detect whether config has changed since last check.

T must be Clone (for get()), Send + Sync (for cross-thread access), and 'static (for use in async tasks).

Implementations

impl<T: Clone + Send + Sync + 'static> SharedConfig<T>

pub fn new(config: T) -> Self

Create a new shared config from an initial value.

Version starts at 0. First update() bumps to 1.

pub fn read(&self) -> RwLockReadGuard<'_, T>

Read the current configuration (zero-copy).

Returns a read guard that holds the lock. Multiple readers can hold the lock simultaneously. Prefer this over get() when you don’t need to hold the config across await points.

pub fn get(&self) -> T

Get a clone of the current configuration.

Use when you need to hold the config across await points or pass it to other functions. For read-only access in synchronous code, prefer read() or with().

pub fn with<F, R>(&self, f: F) -> R

where F: FnOnce(&T) -> R,

Access configuration via a closure (avoids cloning).

The closure receives a reference to the current config while holding the read lock. Useful for extracting a few fields without cloning the entire struct.

pub fn version(&self) -> u64

Get the current config version.

Version is 0 after creation, incremented by 1 on each update(). Monotonically increasing – never decreases.

pub fn update(&self, new_config: T)

Update the configuration atomically.

This will:

1. Acquire write lock and replace the config
2. Increment the version counter
3. Notify all subscribers via the watch channel

pub fn subscribe(&self) -> Receiver<u64>

Subscribe to configuration changes.

Returns a watch::Receiver<u64> that yields the new version number on each config update. Use rx.changed().await to wait for the next change.

let mut rx = shared.subscribe();
loop {
    rx.changed().await.unwrap();
    let version = *rx.borrow();
    let config = shared.get();
    // React to config change...
}

Trait Implementations

impl<T: Clone + Send + Sync + 'static> Clone for SharedConfig<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Clone + Send + Sync + 'static> Debug for SharedConfig<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Clone + Send + Sync + Default + 'static> Default for SharedConfig<T>

fn default() -> Self

Returns the “default value” for a type.