On Tue, Jun 2, 2020 = at 4:06 PM Patrick Williams <patric= k@stwcx.xyz> wrote:

On Mon, Jun 01, 2020 at 11:07:46PM -0700, William Kennington wro= te:
> If you use the fmt library it would only require one extra temporary s= tring
> to be constructed and it works trivially with something like phosphor<= br> > logging.
>
> log<level::INFO>(fmt::format("My error: {}", filename)= );
>
> It also has the advantage of understanding basic c++ types like
> std::strings and std::string_views.
>
> On Mon, Jun 1, 2020 at 8:33 PM =E9=83=81=E9=9B=B7 <yulei.sh@bytedance.com> = wrote:
>
> > I have a bit concern about this. The existing phosphor-logging AP= I
> > does not support this well.
> > Specifically, it does not support the "printf" way to g= enerate a
> > string with the variables to log.
> > So previously we typically put the variables in entries.
> > I do agree that logging the variables in the MESSAGE field is muc= h better.
> > But to encourage such logging, the logging API should be enhanced= to
> > support the "printf" way.
> > E.g.
> >=C2=A0 =C2=A0 =C2=A0log<level::INFO>("Something is wron= g: %s:%d", xx, xxx);
> > is much better than:
> >=C2=A0 =C2=A0 =C2=A0std::string to_log =3D xxx; // generate the me= ssage manually
> >=C2=A0 =C2=A0 =C2=A0log<level::INFO>(to_log);
> >
> > Otherwise, it's really not convenient to write such logging c= ode.
> >

Separate from this proposal from Brad, I'd like to work on a
next-generation of phosphor-logging.=C2=A0 When we originally implemented phosphor-logging we were all pretty new to C++14.=C2=A0 I think there can b= e
some great improvement in the syntax of phosphor-logging now that we
have C++17 (and more experience).

The biggest change I'd like to do is in the way the structured entries<= br> are defined, but I think we can improve the verbosity of syntax in
making a log in general.

Some example syntax:

// Current syntax (and I'm being especially verbose on the namespaces).=
phosphor::logging::log<phosphor::logging::level::ERR>("Some mess= age",
=C2=A0 =C2=A0 phosphor::logging::entry("EXAMPLE=3D%s"), example_s= tr);

// Potential syntax
lg::error("Some message", "EXAMPLE"_s, example_str);
In a code-review I was on, we had some discussions about how difficult
it is to create data that isn't in the "-o verbose" and I thi= nk William
and Lei are both referring to that as well.=C2=A0 I am concerned that a
generic format leads us more to unstructured logging, which personally I don't like.=C2=A0 My suggestion is that we have some easy syntax to ind= icate
"also put this structured data into the raw message" so that my e= xample
above the message becomes "Some message. EXAMPLE=3D'the string'= ;".

I'd be interested to hear what "next generation logging" othe= rs have in
mind.

--
Patrick Williams