C++ Interface for logger

Question

I am working a big legacy project and need to redo the common logger. I tried to make same logger interface with before to avoiding changing ton of loggers. The reason I need to redo the logger is the old one is syslog UDP which was using built-in library functions, while the new one I'm using GELF UDP.

Suppose I have a log with two parts of message, severity is info. The old interface is like below:

Log_INFO<< "First part message" <<"Second part message"<< endl;

Log_INFO is like 'std::cout', but it has two functionality:

Print out message in the command line.
Collect it in Graylog.

My new function is like below:

//Severity = {debug,info,warning, error, critical}
Log(Severity, whole_message)

For the same example,

Log("info",first_part_message+ second_part_message)

My question is how can I make my function is able to read log like the old one.

What's wrong with the old interface? Especially considering that `first_part_message+ second_part_message` will likely not work very well for all but a few cases. — Some programmer dude, Oct 21 '22 at 17:02
Did you ask the question previously, something about turning the `log` function into a macro, or I am just having deja vu? I very particularly remember responding to a question also with the variable name `Log_INFO`... — cs1349459, Oct 21 '22 at 17:54
I just added more explanation for this question. I'm sorry for the confusion. — Alanaa, Oct 21 '22 at 18:00

score 0 · Answer 1 · answered Oct 21 '22 at 19:18

One common way of doing this is creating a custom streambuf-derived class, say LogStreambuf, and an ostream-derived class, say LogStream, that uses LogStreambuf (but is otherwise a plain jane ostream).

Then your log objects would be

LogStream Log_INFO("info");
LogStream Log_WARN("warn");

etc.

Your custom streambuf probably should call your Log function from its sync method.

See e.g. this for an example, and this for further guidance.

C++ Interface for logger

1 Answers1