# Async WRR Queue

this is a wrapping of `weighted round-robin`
schedule algorithm, utilizing [atomic operation](https://doc.rust-lang.org/std/sync/atomic/struct.AtomicUsize.html)
and cache queue in order to avoid lock latency or the schedule latency. And we have
used an async [RwLock](https://docs.rs/tokio/latest/tokio/sync/struct.RwLock.html)
(feature `default` or `tokio`) to overcome the conflict of select instance and
recalculate queue.

[LinkToCratesIO](https://crates.io/crates/async_wrr_queue)

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[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)

- async interface for tokio
- Atomic operation aimed to provide the best run-time performance
- dynamic insert supported

more detailed documented [WrrQueue](https://docs.rs/async_wrr_queue/latest/async_wrr_queue/struct.WrrQueue.html) |
[Instance](https://docs.rs/async_wrr_queue/latest/async_wrr_queue/struct.Instance.html)

## Example

```rust
use async_wrr_queue::*;

#[tokio::main]
async fn main() {
    let mut queue = WrrQueue::new();

    // insert many
    queue.insert_many(vec![("a", 1usize), ("b", 2usize)]).await;

    // insert one
    queue.insert(("c", 3usize)).await;
    queue.insert_many(vec![("d", 5usize), ("e", 2usize)]).await;

    // schedule!
    let mut result = Vec::new();
    for _ in 0..30 {
      result.push(queue.select().await.unwrap().data().clone());
    }

    // expected to be this sequence:
    assert_eq!(result, Vec::from_iter( [ "d", "c", "b", "d", "e", "d", "c", "a", "d", "b", "e", "c", "d"].into_iter().cycle().take(30)));
}
```

## features

- `default` : `tokio`
- `tokio` : async interface, using `tokio::sync::RwLock` to guarantee best performance
- `blocking` : not compatible with `tokio`, using `std::sync::RwLock` for blocking acquire