OpenBMC Logging and Error Handling Dos and Don'ts
Johnathan Mantey
johnathanx.mantey at intel.com
Thu Jun 4 05:17:53 AEST 2020
I would like it to be easier to determine how to change the error
message level.
I don't bother with the log code because I don't know where it's controlled.
On 6/3/20 12:02 PM, Vijay Khemka wrote:
>
> On 6/2/20, 5:08 PM, "openbmc on behalf of Vernon Mauery" <openbmc-bounces+vijaykhemka=fb.com at lists.ozlabs.org on behalf of vernon.mauery at linux.intel.com> wrote:
>
> On 02-Jun-2020 06:06 PM, Patrick Williams wrote:
> >On Mon, Jun 01, 2020 at 11:07:46PM -0700, William Kennington wrote:
> >> If you use the fmt library it would only require one extra temporary string
> >> to be constructed and it works trivially with something like phosphor
> >> 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 郁雷 <yulei.sh at bytedance.com> wrote:
> >>
> >> > I have a bit concern about this. The existing phosphor-logging API
> >> > does not support this well.
> >> > Specifically, it does not support the "printf" way to generate 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 much better.
> >> > But to encourage such logging, the logging API should be enhanced to
> >> > support the "printf" way.
> >> > E.g.
> >> > log<level::INFO>("Something is wrong: %s:%d", xx, xxx);
> >> > is much better than:
> >> > std::string to_log = xxx; // generate the message manually
> >> > log<level::INFO>(to_log);
> >> >
> >> > Otherwise, it's really not convenient to write such logging code.
> >> >
> >
> >Separate from this proposal from Brad, I'd like to work on a
> >next-generation of phosphor-logging. When we originally implemented
> >phosphor-logging we were all pretty new to C++14. I think there can be
> >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
> >are defined, but I think we can improve the verbosity of syntax in
> >making a log in general.
>
> One more change I would like to see is a way to actually have the real
> filename and line number show up in the systemd log. Right now the
> filename and line number are always the logger code:
> CODE_LINE=76
> CODE_FUNC=helper_log
> CODE_FILE=.../usr/include/phosphor-logging/log.hpp
>
> It will be good if we can have debug as a level and somehow we can see
> messages from debug by enabling or disabling.
>
> It looks like C++20 has a shiny new helper for this: source_location
> https://urldefense.proofpoint.com/v2/url?u=https-3A__en.cppreference.com_w_cpp_experimental_source-5Flocation&d=DwIFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=v9MU0Ki9pWnTXCWwjHPVgpnCR80vXkkcrIaqU7USl5g&m=qFbu7FdFQSHVMy4ZvMtHDH5RzYQnqMUQ_T0h4qL0Xd0&s=QRsbQvb4LKAEoa8AITFyPFhcoCSVHtFLMOU66UodPnM&e=
>
> --Vernon
>
> >Some example syntax:
> >
> >// Current syntax (and I'm being especially verbose on the namespaces).
> >phosphor::logging::log<phosphor::logging::level::ERR>("Some message",
> > phosphor::logging::entry("EXAMPLE=%s"), example_str);
> >
> >// 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 think William
> >and Lei are both referring to that as well. I am concerned that a
> >generic format leads us more to unstructured logging, which personally I
> >don't like. My suggestion is that we have some easy syntax to indicate
> >"also put this structured data into the raw message" so that my example
> >above the message becomes "Some message. EXAMPLE='the string'".
> >
> >I'd be interested to hear what "next generation logging" others have in
> >mind.
> >
> >--
> >Patrick Williams
>
>
>
--
Johnathan Mantey
Senior Software Engineer
*azad te**chnology partners*
Contributing to Technology Innovation since 1992
Phone: (503) 712-6764
Email: johnathanx.mantey at intel.com <mailto:johnathanx.mantey at intel.com>
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