Block on full channel?

[rmccue]

Currently, we're using Tokio's channels for the .await support in AsyncLogger::run. This means we need to use Sender::try_send since Tokio's Sender::send is async, and io::Write needs to be synchronous.

However, this also means if the buffer is full, we can't write that data out, and we don't block on it. Instead, we return a io::ErrorKind::OutOfMemory.

Unfortunately, asciinema doesn't seem to do anything with this (like apply backpressure to the stream), so we silently drop logs instead. This is unfortunate, particularly if you're using the logging functionality for security-oriented purposes (like an audit log).

This might be fixable by switching to std::sync::mpsc::sync_channel instead, whose Sender::send is blocking (or std::sync::mpsc::channel which has an "infinite buffer", no idea how that works) - however, this means the Receiver side can't use timeout().await and needs to use recv_timeout instead.

Not sure on the implications or if this will even work - or if blocking is even desirable! tbd.