How to use Monitor & Backend?

[Frankkkkk]

Hi,

First of all thank you for this nice work!
I was trying to run two workers at the same time, but can't make the example work the way it's show on the readme.

What I have:

#[tokio::main]
async fn main() {
    let pool = get_pg_pool().await;
    let mut email_backend = PostgresStorage::new(&pool);
    let mut reminder_backend = PostgresStorage::new(&pool);

    let monitor = Monitor::new()
        .on_event(|ctx, event| println!("{}: {:?}", ctx.name(), event))
        .register(move |_| {
            let a = WorkerBuilder::new("email-worker")
                .backend(email_backend)
                .build(send_email_job);
            a
        })
        .register(move |_| {
            let b = WorkerBuilder::new("reminder-worker")
                .backend(reminder_backend)
                .build(send_reminder);
            b
        });

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

But it says:

error[E0507]: cannot move out of `reminder_backend`, a captured variable in an `Fn` closure
   --> src/bin/worker.rs:22:26
    |
 10 |     let mut reminder_backend = PostgresStorage::new(&pool);
    |         --------------------   --------------------------- move occurs because `reminder_backend` has type `apalis_postgres::PostgresStorage<Remind>`, which does not implement the `Copy` trait
    |         |
    |         captured outer variable
...
 20 |         .register(move |_| {
    |                   -------- captured by this `Fn` closure
 21 |             let b = WorkerBuilder::new("reminder-worker")
 22 |                 .backend(reminder_backend)
    |                          ^^^^^^^^^^^^^^^^ `reminder_backend` is moved here

What works:

async fn main() {
    let pool = get_pg_pool().await;
    let pool_b = get_pg_pool().await;

    let monitor = Monitor::new()
        .on_event(|ctx, event| println!("{}: {:?}", ctx.name(), event))
        .register(move |_| {
            let mut email_backend = PostgresStorage::new(&pool);
            let a = WorkerBuilder::new("email-worker")
                .backend(email_backend)
                .build(send_email_job);
            a
        })
        .register(move |_| {
            let mut reminder_backend = PostgresStorage::new(&pool_b);
            let b = WorkerBuilder::new("reminder-worker")
                .backend(reminder_backend)
                .build(send_reminder);
            b
        });

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

But it's rather ugly to duplicate the pool for each backend?

I'm sure I'm doing something wrong, but I don't see it right now

Thanks and cheers!
Frank

[geofmureithi]

Have you looked at this example?

You have a move problem where the register callback needs Clone since Monitor may need to restart a Worker.

[Frankkkkk]

It looks like the PostgresStorage doesn't implement clone:

the trait bound `PgFetcher<_, Vec<u8>, apalis_codec::json::JsonCodec<Vec<u8>>>: Clone` is not satisfied
required for `PgFetcher<SendEmail, Vec<u8>, apalis_codec::json::JsonCodec<Vec<u8>>>` to implement `Clone`
1 redundant requirement hidden
required for `apalis_postgres::PostgresStorage<SendEmail>` to implement `Clone`

[geofmureithi]

That is a bug, It should be a straight forward fix. Will do a fix ASAP

[geofmureithi]

https://docs.rs/apalis-postgres/latest/apalis_postgres/struct.PgFetcher.html#impl-Clone-for-PgFetcher%3CArgs,+Compact,+Decode%3E

The problem is that it expects Args to be clone and I guess SendEmail is not.

Making your SendEmail clone might fix this for now

[Frankkkkk]

Hey, you're right, that fixes it. Sorry for the hassle, and thanks!

[geofmureithi]

Reopening this to allow Clone without Args being Clone