`.await` in a #[query] function

Developers Rust
1

I’m integrating Turso database in my canister and it requires database calls to be async

#[query]
async fn query_something() -> Vec<String> {
    with_connection(async |c| {
        Something::query_all(&c).await
    })
    .await
    .expect("failed to read all")
}

This fails with:

Canister called `ic0.trap` with message: 'Panicked at 'protected task outlived its canister method (did you mean to use spawn_weak or spawn_migratory?)'

If I change query to update then all is good. Is there a way to call async functions from query functions? In this case, the async is just how the API works and under the hood, it’s just calling stable storage

2

If (and only if) there is no true asynchrony occurring, you can call futures::executor::block_on.

3

What are consequences of getting my assumption of no no true asynchrony happening wrong?

4

The only source of true asynchrony on the IC is inter-canister calls. If you aren’t making one internally, it isn’t truly async; and if you make one and try to block on it, you will get a trap saying that you exceeded the instruction limit (or that you failed to reply).

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