Crate piscina 

A simple generic pool that supports both sync and async.

Two types of pools are provided:

• Pool: A simple pool that supports both sync and async.
• PriorityPool: A pool of items with priorities and supports both sync and async.

This crate internally utilizes futures_channel::oneshot and is thus lock-free.

Features

default = []

The features below are related to logging errors, which should be unreachable.

• log: Enables logging using the log crate.
• tracing: Enables logging using the tracing crate.

Examples

Non-async Pool example:

use piscina::Pool;

let mut pool = Pool::new();
pool.put(1);
pool.put(2);

let item1 = pool.try_get();
assert!(item1.is_some());

let item2 = pool.blocking_get();

let none = pool.try_get();
assert!(none.is_none());

drop(item1); // Return the item to the pool by dropping it
let item3 = pool.try_get();
assert!(item3.is_some());

Async Pool example:

use piscina::Pool;

futures::executor::block_on(async {
    let mut pool = Pool::new();
    pool.put(1);
    pool.put(2);

    let item1 = pool.get().await;
    let item2 = pool.get().await;

    let none = pool.try_get();
    assert!(none.is_none());

    drop(item1); // Return the item to the pool by dropping it
    let item3 = pool.get().await;
});

Non-async PriorityPool example:

use piscina::PriorityPool;
 
let mut pool = PriorityPool::new();
pool.put("hello", 1);
pool.put("world", 2); // Larger value means higher priority.
 
// Get the highest priority item.
let item = pool.try_get();
assert!(item.is_some());
let item = item.unwrap();
assert_eq!(item.item(), &"world");
 
let another_item = pool.try_get();
assert!(another_item.is_some());
let another_item = another_item.unwrap();
assert_eq!(another_item.item(), &"hello");
 
// The pool is now empty.
let empty_item = pool.try_get();
assert!(empty_item.is_none());
 
drop(another_item); // Return the item back to the pool by dropping it.
let hello = pool.try_get();
assert!(hello.is_some());
assert_eq!(hello.unwrap().item(), &"hello");

Async PriorityPool example:

use piscina::PriorityPool;
 
let mut pool = PriorityPool::new();
pool.put("hello", 1);
pool.put("world", 2); // Larger value means higher priority.
 
futures::executor::block_on(async {
    // Get the highest priority item.
    let world = pool.get().await;
    assert_eq!(world.item(), &"world"); 

    let hello = pool.get().await;
    assert_eq!(hello.item(), &"hello");
 
    // The pool is now empty.
    drop(hello); // Return the item back to the pool by dropping it.
    let item = pool.get().await;
    assert_eq!(item.item(), &"hello"); 
});

Safety

Instead of using an Option, this crate uses unsafe code ManuallyDrop in PooledItem. And the only use of unsafe code ManuallyDrop::take() occurs when PooledItem is dropped.

Re-exports

pub use pool::Pool;

pub use priority::PriorityPool;

Modules

pool

Regular pool

priority

Priority pool.