tests-integration/tests/pool_behavior_test.rs

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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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use std::convert::Infallible;
use std::panic::AssertUnwindSafe;
use std::panic::catch_unwind;
use std::sync::Arc;
use std::sync::atomic::AtomicUsize;
use std::sync::atomic::Ordering;
use std::time::Instant;

use asyncband::pool::ManageObject;
use asyncband::pool::ObjectStatus;
use asyncband::pool::QueueStrategy;
use asyncband::pool::bounded;
use asyncband::pool::unbounded;

struct CountingManager {
    next: Arc<AtomicUsize>,
    detached: Arc<AtomicUsize>,
}

impl ManageObject for CountingManager {
    type Object = usize;
    type Error = Infallible;

    async fn create(&self) -> Result<Self::Object, Self::Error> {
        Ok(self.next.fetch_add(1, Ordering::Relaxed))
    }

    async fn is_recyclable(
        &self,
        _object: &mut Self::Object,
        _status: &ObjectStatus,
    ) -> Result<(), Self::Error> {
        Ok(())
    }

    fn on_detached(&self, object: &mut Self::Object) {
        self.detached.fetch_add(1, Ordering::Relaxed);
        *object += 1000;
    }
}

#[test]
#[should_panic(expected = "bounded pool max_size must be greater than zero")]
fn bounded_pool_rejects_zero_capacity() {
    bounded::Pool::new(
        bounded::PoolConfig::new(0),
        CountingManager {
            next: Arc::new(AtomicUsize::new(0)),
            detached: Arc::new(AtomicUsize::new(0)),
        },
    );
}

#[test]
fn bounded_construction_allocates_idle_storage_lazily() {
    let pool = bounded::Pool::new(
        bounded::PoolConfig::new(usize::MAX),
        CountingManager {
            next: Arc::new(AtomicUsize::new(0)),
            detached: Arc::new(AtomicUsize::new(0)),
        },
    );

    assert_eq!(pool.status().max_size, usize::MAX);
    assert_eq!(pool.status().current_size, 0);
    assert_eq!(pool.status().idle_count, 0);
}

#[tokio::test]
async fn bounded_last_used_tracks_the_end_of_a_checkout() {
    let pool = bounded::Pool::new(
        bounded::PoolConfig::new(1),
        CountingManager {
            next: Arc::new(AtomicUsize::new(0)),
            detached: Arc::new(AtomicUsize::new(0)),
        },
    );

    let object = pool.get().await.unwrap();
    let before_return = Instant::now();
    drop(object);

    let object = pool.get().await.unwrap();
    assert!(object.status().last_used() >= before_return);
    assert_eq!(object.status().recycle_count(), 1);
}

#[tokio::test]
async fn retain_invokes_detachment_hook_once_per_removed_object() {
    let detached = Arc::new(AtomicUsize::new(0));
    let pool = bounded::Pool::new(
        bounded::PoolConfig::new(4),
        CountingManager {
            next: Arc::new(AtomicUsize::new(0)),
            detached: detached.clone(),
        },
    );

    let mut objects = vec![];
    for _ in 0..4 {
        objects.push(pool.get().await.unwrap());
    }
    drop(objects);

    let mut result = pool.retain(|object, _status| *object % 2 == 0);
    result.removed.sort_unstable();

    assert_eq!(result.retained, 2);
    assert_eq!(result.removed, [1001, 1003]);
    assert_eq!(detached.load(Ordering::Relaxed), 2);
    assert_eq!(pool.status().current_size, 2);
    assert_eq!(pool.status().idle_count, 2);
}

#[test]
fn manual_pool_try_get_tracks_return_time() {
    let pool = unbounded::Pool::<usize>::never_manage(unbounded::PoolConfig::default());
    assert!(pool.try_get().is_none());

    pool.extend_one(42);
    let object = pool.try_get().unwrap();
    assert_eq!(object.status().recycle_count(), 1);

    let before_return = Instant::now();
    drop(object);

    let object = pool.try_get().unwrap();
    assert!(object.status().last_used() >= before_return);
    assert_eq!(object.status().recycle_count(), 2);
}

#[test]
fn manual_pool_honors_fifo_and_lifo_order() {
    fn drain(strategy: QueueStrategy) -> Vec<usize> {
        let config = unbounded::PoolConfig::new().with_queue_strategy(strategy);
        let pool = unbounded::Pool::<usize>::never_manage(config);
        pool.extend([1, 2, 3]);

        (0..3).map(|_| pool.try_get().unwrap().detach()).collect()
    }

    assert_eq!(drain(QueueStrategy::Fifo), [1, 2, 3]);
    assert_eq!(drain(QueueStrategy::Lifo), [3, 2, 1]);
}

#[test]
fn retain_predicate_panic_preserves_pool_ownership() {
    let pool = unbounded::Pool::<usize>::never_manage(unbounded::PoolConfig::default());
    pool.extend([1, 2, 3, 4]);

    let result = catch_unwind(AssertUnwindSafe(|| {
        pool.retain(|object, _status| {
            assert_ne!(*object, 3, "predicate panic");
            *object % 2 == 0
        });
    }));
    assert!(result.is_err());
    assert_eq!(pool.status().current_size, 4);
    assert_eq!(pool.status().idle_count, 4);

    let mut objects = (0..4)
        .map(|_| pool.try_get().unwrap().detach())
        .collect::<Vec<_>>();
    objects.sort_unstable();
    assert_eq!(objects, [1, 2, 3, 4]);
}