Async vs Sync handlers

[valkrypton]

I am implementing api endpoints for my web app, and I am not sure whether to make the handlers async or sync. The endpoints mostly consist of calls to other function that do basic CRUD operations. I have made them async right now purely based on intuition, but I don't actually know what should I opt for as having both async and sync handlers seems to not make a difference.

[jbcurtin]

Hi @valkrypton ,

If you use tokio to manage the runtime. You probably will never notice a difference in performance between sync/async handlers until there is a lot of file or network io.

[the10thWiz]

Rocket starts a tokio runtime, and every method is executed on the async runtime. The general advice I would give, is that you should always use tokio types for doing any kind of IO, especially network/file IO. Handlers only need to be marked as async if you use any of these types, and call .await inside them. Clippy has a warning for async functions that don't use .await, but it's up to you whether you remove the async marker from your functions that don't need it.