-- -For some lightweight background tasks, it's cheaper to run them on the same thread using async instead of starting one thread per worker. That's why we implemented this kind of processing in fang. Its key features: - -- Each worker is started as a tokio task -- If any worker fails during task execution, it's restarted -- Tasks are saved to a Postgres database. Instead of diesel, [tokio-postgres](https://github.com/sfackler/rust-postgres) is used to interact with a db. The threaded processing uses the [diesel](https://github.com/diesel-rs/diesel) ORM which blocks the thread. -- The implementation is based on traits so it's easy to implement additional backends (redis, in-memory) to store tasks. - -## Usage - -The usage is straightforward: - -1. Define a serializable task by adding `serde` derives to a task struct. -2. Implement `AsyncRunnable` runnable trait for fang to be able to run it. -3. Start workers. -4. Enqueue tasks. - -Let's go over each step. - -### Define a job - -```rust -use fang::serde::{Deserialize, Serialize}; - -#[derive(Serialize, Deserialize)] -#[serde(crate = "fang::serde")] -pub struct MyTask { - pub number: u16, -} - -impl MyTask { - pub fn new(number: u16) -> Self { - Self { number } - } -} -``` - -Fang re-exports `serde` so it's not required to add it to the `Cargo.toml` file - - -### Implement the AsyncRunnable trait - -```rust -use fang::async_trait; -use fang::typetag; -use fang::AsyncRunnable; -use std::time::Duration; - -#[async_trait] -#[typetag::serde] -impl AsyncRunnable for MyTask { - async fn run(&self, queue: &mut dyn AsyncQueueable) -> Result<(), Error> { - let new_task = MyTask::new(self.number + 1); - queue - .insert_task(&new_task as &dyn AsyncRunnable) - .await - .unwrap(); - - log::info!("the current number is {}", self.number); - tokio::time::sleep(Duration::from_secs(3)).await; - - Ok(()) - } -} - -``` - -- Fang uses the [typetag library](https://github.com/dtolnay/typetag) to serialize trait objects and save them to the queue. -- The [async-trait](https://github.com/dtolnay/async-trait) is used for implementing async traits - -### Init queue - -```rust -use fang::asynk::async_queue::AsyncQueue; - -let max_pool_size: u32 = 2; -let mut queue = AsyncQueue::builder() - .uri("postgres://postgres:postgres@localhost/fang") - .max_pool_size(max_pool_size) - .duplicated_tasks(true) - .build(); -``` - - -### Start workers - -```rust -use fang::asynk::async_worker_pool::AsyncWorkerPool; -use fang::NoTls; - -let mut pool: AsyncWorkerPool-Async provides significantly reduced CPU and memory overhead, especially for workloads with a large amount of IO-bound tasks, such as servers and databases. All else equal, you can have orders of magnitude more tasks than OS threads, because an async runtime uses a small amount of (expensive) threads to handle a large amount of (cheap) tasks -
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