Should SftpSession and Channel be wrapped in an Arc for thread safety or not?

[kanpov]

Title

[Eugeny]

Most russh things are Send but not Sync if that's what you're asking.

[kanpov]

Most russh things are Send but not Sync if that's what you're asking.

I'm new to Rust, so not being Sync does mean it should be wrapped in an Arc to be able to be shared across threads?

[Eugeny]

Typically you wouldn't concert yourself with this when writing an async tokio based application. Objects such as your russh Handles would never be accessed from multiple threads simultaneously (Sync) but instead moved between threads (Send).

Thread safety usually only becomes relevant when you're trying to fuse an async library into your thread-based non-async application

[kanpov]

Typically you wouldn't concert yourself with this when writing an async tokio based application. Objects such as your russh Handles would never be accessed from multiple threads simultaneously (Sync) but instead moved between threads (Send).

Thread safety usually only becomes relevant when you're trying to fuse an async library into your thread-based non-async application

So if I'm writing a library (which is what I'm doing right now) where an SftpSession for SFTP and Channel<Msg> for SSH are shared between threads, I would need neither Arc nor Mutex?

[Eugeny]

Depends on what you're doing. If you actually share the reference to the structs between your own threads, you need to wrap it in Arc<Mutex> like every other non-Sync object. If the moving only happens due to async futures migrating between executor threads, you don't need it.