Child or sub logger

[jasonbeach]

spdlog is pretty fantastic...basically my standard has become every class I write has a spdlog logger in it. cout is basically banned--if it's worth couting then i's worth sending it to a logger with a console sink. What I'm trying to figure out is the best way to "nest" loggers--i.e. if class A has its logger, class B and C both contain class A as well as have their loggers. I have my own Logger::get helper function which queries the global registry for a logger and return it if it's found or creates it if it's not. So each class has:

LoggerPtr logger_ = Logger::get("Foo");

where the logger's name is set. Behind the scenes when the logger is created, the format is set so the class name (Foo in this case) is printed as part of the log statement. All loggers are going to the same file sink. Unfortunately with this arrangement it's not possible tell which statements came from the class B::A logger vs the class C::A logger.

I guess instead of setting each logger name statically, I can add a logger "namespace" argument to each class's constructor, but I was really trying to not have any logger arguments in the constructor. I guess there's not really a way to associate the loggers with each without either making them public (they're typically private) or feeding them in through a constructor or some other public function. Just wondering what other people have tried.

[tt4g]

How about separating the names of parent and child loggers with a separator (e.g. /)?

auto parent = spdlog::get("Foo");
std::string logger_name = parent->name() + "/" + child_name;
auto child = parent->clone(logger_name);

[jasonbeach]

that would probably work...what does the line:
auto child = parent->close(logger_name);

do?

[tt4g]

Oh... Sorry close is typo. clone is correct (edited).

[tt4g]

spdlog::logger::clone(std::string) creates new logger with a new name. It copies the sink and level of the original logger.

spdlog/include/spdlog/logger-inl.h

Lines 157 to 163 in 6a9d561

	// create new logger with same sinks and configuration.
	SPDLOG_INLINE std::shared_ptr<logger> logger::clone(std::string logger_name)
	{
	auto cloned = std::make_shared<logger>(*this);
	cloned->name_ = std::move(logger_name);
	return cloned;
	}

spdlog/include/spdlog/logger-inl.h

Lines 19 to 26 in 6a9d561

	SPDLOG_INLINE logger::logger(const logger &other)
	: name_(other.name_)
	, sinks_(other.sinks_)
	, level_(other.level_.load(std::memory_order_relaxed))
	, flush_level_(other.flush_level_.load(std::memory_order_relaxed))
	, custom_err_handler_(other.custom_err_handler_)
	, tracer_(other.tracer_)
	{}