Feature Request

Add a way to enable logging the PID for each log line in tracing-subscriber.

Crates

tracing-subscriber

Motivation

Sometimes you spawn many processes in the same terminal, and want to figure out which is logging what.

Proposal

There is already .with_thread_ids(true), so I suggest adding a .with_pid(true);

A more general solution would be .with_custom_string(std::process::id().to_string()).

Alternatives

Users can already implement it with a custom formatter, but it is a lot of work and not a lot of docs.

I believe one has to write a FormatEvent via SubscriberBuilder::event_format. One can look at https://github.com/davidbarsky/tracing-glog/ and try to do something similar, but again - it is a lot of work.