apalis-postgres

Background task processing in rust using apalis and postgres

Features

• Reliable job queue using Postgres as the backend.
• Multiple storage types: standard polling and trigger based storages.
• Custom codecs for serializing/deserializing job arguments as bytes.
• Heartbeat and orphaned job re-enqueueing for robust task processing.
• Integration with apalis workers and middleware.

Storage Types

• [PostgresStorage]: Standard polling-based storage.
• [PostgresStorageWithListener]: Event-driven storage using Postgres NOTIFY for low-latency job fetching.
• [SharedPostgresStorage]: Shared storage for multiple job types, uses Postgres NOTIFY.

The naming is designed to clearly indicate the storage mechanism and its capabilities, but under the hood the result is the PostgresStorage struct with different configurations.

Examples

Basic Worker Example

#[tokio::main]
async fn main() {
    let pool = PgPool::connect(env!("DATABASE_URL").unwrap()).await.unwrap();
    PostgresStorage::setup(&pool).await.unwrap();
    let mut backend = PostgresStorage::new(&pool);

    let mut start = 0;
    let mut items = stream::repeat_with(move || {
        start += 1;
        let task = Task::builder(start)
            .run_after(Duration::from_secs(1))
            .with_ctx(SqlContext::new().with_priority(1))
            .build();
        Ok(task)
    })
    .take(10);
    backend.send_all(&mut items).await.unwrap();

    async fn send_reminder(item: usize, wrk: WorkerContext) -> Result<(), BoxDynError> {
        Ok(())
    }

    let worker = WorkerBuilder::new("worker-1")
        .backend(backend)
        .build(send_reminder);
    worker.run().await.unwrap();
}

NOTIFY listener example

#[tokio::main]
async fn main() {
    let pool = PostgresPool::connect(env!("DATABASE_URL").unwrap()).await.unwrap();
    PostgresStorage::setup(&pool).await.unwrap();

    let lazy_strategy = StrategyBuilder::new()
        .apply(IntervalStrategy::new(Duration::from_secs(5)))
        .build();
    let config = Config::new("queue")
        .with_poll_interval(lazy_strategy)
        .set_buffer_size(5);
    let backend = PostgresStorage::new_with_notify(&pool, &config).await;

    tokio::spawn({
        let pool = pool.clone();
        let config = config.clone();
        async move {
            tokio::time::sleep(Duration::from_secs(2)).await;
            let mut start = 0;
            let items = stream::repeat_with(move || {
                start += 1;
                Task::builder(serde_json::to_vec(&start).unwrap())
                    .run_after(Duration::from_secs(1))
                    .with_ctx(SqlContext::new().with_priority(start))
                    .build()
            })
            .take(20)
            .collect::<Vec<_>>()
            .await;
            apalis_postgres::sink::push_tasks(pool, config, items).await.unwrap();
        }
    });

    async fn send_reminder(item: usize, wrk: WorkerContext) -> Result<(), BoxDynError> {
        Ok(())
    }

    let worker = WorkerBuilder::new("worker-2")
        .backend(backend)
        .build(send_reminder);
    worker.run().await.unwrap();
}

Workflow Example

#[tokio::main]
async fn main() {
    let workflow = WorkFlow::new("odd-numbers-workflow")
        .then(|a: usize| async move {
            Ok::<_, WorkflowError>((0..=a).collect::<Vec<_>>())
        })
        .filter_map(|x| async move {
            if x % 2 != 0 { Some(x) } else { None }
        })
        .filter_map(|x| async move {
            if x % 3 != 0 { Some(x) } else { None }
        })
        .filter_map(|x| async move {
            if x % 5 != 0 { Some(x) } else { None }
        })
        .delay_for(Duration::from_millis(1000))
        .then(|a: Vec<usize>| async move {
            println!("Sum: {}", a.iter().sum::<usize>());
            Ok::<(), WorkflowError>(())
        });

    let pool = PostgresPool::connect(env!("DATABASE_URL")).await.unwrap();
    PostgresStorage::setup(&pool).await.unwrap();
    let mut backend = PostgresStorage::new_in_queue(&pool, "test-workflow");

    backend.push(100usize).await.unwrap();

    let worker = WorkerBuilder::new("rango-tango")
        .backend(backend)
        .on_event(|ctx, ev| {
            println!("On Event = {:?}", ev);
            if matches!(ev, Event::Error(_)) {
                ctx.stop().unwrap();
            }
        })
        .build(workflow);

    worker.run().await.unwrap();
}

Shared Example

This shows an example of multiple backends using the same connection. This can improve performance if you have many types of jobs.

#[tokio::main]
async fn main() {
    let pool = PgPool::connect(env!("DATABASE_URL"))
        .await
        .unwrap();
    let mut store = SharedPostgresStorage::new(pool);

    let mut map_store = store.make_shared().unwrap();

    let mut int_store = store.make_shared().unwrap();

    map_store
        .push_stream(&mut stream::iter(vec![HashMap::<String, String>::new()]))
        .await
        .unwrap();
    int_store.push(99).await.unwrap();

    async fn send_reminder<T, I>(
        _: T,
        task_id: TaskId<I>,
        wrk: WorkerContext,
    ) -> Result<(), BoxDynError> {
        tokio::time::sleep(Duration::from_secs(2)).await;
        wrk.stop().unwrap();
        Ok(())
    }

    let int_worker = WorkerBuilder::new("rango-tango-2")
        .backend(int_store)
        .build(send_reminder);
    let map_worker = WorkerBuilder::new("rango-tango-1")
        .backend(map_store)
        .build(send_reminder);
    tokio::try_join!(int_worker.run(), map_worker.run()).unwrap();
}

Observability

You can track your jobs using apalis-board.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.