Struct ConnectionTracker 

pub struct ConnectionTracker { /* private fields */ }

Tracks the per-server NNTP connection budget. Each server has a tokio::sync::Semaphore whose initial permit count is the configured connections limit. Workers acquire a permit before connecting and hold it for their entire lifetime; the permit’s Drop releases the slot synchronously back to the pool. This makes over-allocation a type-level impossibility — once limit permits are out, the next acquire awaits.

Limit changes at runtime are handled differently for grow vs shrink:

• Grow (e.g. 5 → 10): the existing semaphore is given the additional permits via add_permits; existing slot holders are unaffected.
• Shrink (e.g. 10 → 5): the entire ServerSlot is replaced with a fresh one. Old permit holders continue to reference the orphaned semaphore via their Arc; their drops release back to it (a no-op since nothing else points at it). Workers detect the replacement via ConnectionTracker::slot_is_current and exit on the next iteration.

Implementations

impl ConnectionTracker

pub fn new() -> Self

pub fn set_limit(&self, server_id: &str, server_name: &str, limit: usize)

Set or update the per-server connection limit.

• First call for a server_id: creates a fresh semaphore with limit permits.
• Subsequent call with the same limit and server_name: no-op.
• Grow (limit > current): adds permits in place.
• Shrink or rename: replaces the slot. Old permit holders detach naturally via [slot_is_current].

pub fn remove_server(&self, server_id: &str)

Forget a server entirely (e.g. on update_servers removing it). Existing permit holders are unaffected; they will detect that their slot is no longer current and exit.

pub async fn acquire(&self, server_id: &str) -> Option<ConnectionSlot>

Acquire a connection slot for server_id. Awaits if the pool is at the limit. Returns None if the server isn’t registered or its limit is zero.

pub fn slot_is_current(&self, slot: &ConnectionSlot) -> bool

Returns true if slot was acquired from the current semaphore for its server. False if the limit was changed (semaphore replaced) or the server was removed — the worker should exit at its next safe checkpoint.

pub fn slot_status(&self, slot: &ConnectionSlot) -> SlotStatus

Like [slot_is_current] but distinguishes the reason a slot is no longer current — useful for diagnostics on the worker exit path.

pub fn snapshot(&self) -> Vec<(String, usize, usize)>

(server_id, active, limit) triples for the live pool. active is derived from the semaphore’s available permits and is always <= limit by construction.

pub fn total(&self) -> usize

Total currently-held permits across all servers in the live pool. Permits held against orphaned (replaced) semaphores are NOT counted — they’ll go away as the holding workers exit.

Trait Implementations

impl Default for ConnectionTracker

fn default() -> Self

Returns the “default value” for a type.