Struct InstancePool 

pub struct InstancePool<T, E>
where
    T: Send + 'static,
    E: PoolResourceLimit + Send + Sync + 'static,
{ /* private fields */ }

A per-plugin instance cache with a concurrency cap.

Generic over the per-invoke instance type T and the loader’s error type E. Production use: InstancePool<extism::Plugin, ExtismError> or InstancePool<ScalarPluginInstance, WasmError>.

Does not reuse instances — every Self::acquire builds a fresh one and every release drops it. See the module docs for why.

Implementations

impl<T, E> InstancePool<T, E>

where T: Send + 'static, E: PoolResourceLimit + Send + Sync + 'static,

pub fn new( cfg: PoolConfig, factory: impl Fn() -> Result<T, E> + Send + Sync + 'static, ) -> Result<Self, E>

Construct a pool that builds fresh instances via factory.

cfg.warm_count is accepted for API compatibility but ignored: nothing is pre-warmed, because instances are never reused.

Errors

This constructor is infallible in practice; the E in the return type is retained so the signature is stable across the refactor.

pub fn acquire(&self) -> Result<T, E>

Acquire a fresh instance, honoring the concurrency cap.

Reserves a live slot (CAS against max_instances), then builds a brand-new instance via the factory. No warm reuse — the returned instance has clean state. Releasing it (via PooledInstance’s drop) frees the slot.

Errors

• E::resource_limit(...) when max_instances is reached.
• Whatever the factory returns on construction failure.

pub fn release(&self, inst: T)

Release an instance, freeing its concurrency slot.

The instance is dropped here (never recycled), so its Drop impl runs any cleanup. A trapped instance is therefore discarded, not handed back out.

pub fn metrics(&self) -> Arc<PoolMetrics>

Snapshot the current metrics.

pub fn config(&self) -> &PoolConfig

Pool configuration, for diagnostics.

Trait Implementations

impl<T, E> Debug for InstancePool<T, E>

where T: Send + 'static, E: PoolResourceLimit + Send + Sync + 'static,

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

Formats the value using the given formatter.