RFC: DTrace probes for debugging or testing in userland programs

[Jordan Hubbard]

> On Dec 19, 2016, at 12:27 PM, Adrian Chadd <adrian.chadd at gmail.com> wrote:
> 
> So although I like the sentiment, I don't think using dtrace for
> program logging is the right answer.  I like what apple did to wrap
> the program logging stuff so people didn't just write their own
> libraries (hi!) and so there's a unified-ish way to interact with
> apple programs. I think we could do with that.

Thanks!

We did a number of other things with ASL (Apple System Logger) which I miss very much today and would hope to see in any FreeBSD equivalent:

1. We structured all log data into dictionaries, so every application and/or subsystem within that application can add its own “tags” without squashing other key information.  This also unified the character encoding format, so some applications were no longer logging in ISO-Latin1, others in UTF-8 and yet others in SHIFT-JIS.

2.  There’s also a logging database, as one of the many possible “output sinks”, so searches / queries are fast (and there’s an API for querying and managing its contents).

3. We added client-side and server side logging filters, so you can “crank an application up” or shut its mouth without having to make any code changes.

4. It’s all thread-safe.

- Jordan