How can I emit a new event from a Subscriber impl?

[andrewbanchich]

I would like to create a subscriber which either mutates events or ignores them and logs new ones.

Is the only / best way of doing this to spawn a new Tokio task and emit the event from there?

[kaffarell]

Just use the event!() macro to emit a new event. Mutating events isn't possible as far as I know.

[kaffarell]

Why would tracing::event!(..) not work?

[andrewbanchich]

I'm not a core tracing dev, so I'm not sure - but it doesn't emit any event if called in a Subscriber impl.

[kaffarell]

Then there is probably something wrong with your Subscriber and/or Filter. I just tried it and it worked with a minimal example. Maybe you could post a minimal snippet of your code so I can have a look at it?

[andrewbanchich]

Emitting an event from the event() handler in Subscriber impls causes a stack overflow. Using println! does not have this issue since it doesn't cause recursion.

[kaffarell]

Hmm, yeah well you can't prevent this...