Boost Log Formatter Using the same string as in keyword

Question

Here is how I set up my loggers:

namespace logger = boost::log;
namespace src = boost::log::sources;
namespace sinks = boost::log::sinks;
namespace expr = boost::log::expressions;
using LEVEL = boost::log::trivial::severity_level;


static void log_Severity(LEVEL level, sender_t sender, std::string message);
static void throw_Severity(LEVEL level, sender_t sender, std::string message);
static std::string getUnescaped(std::string input);
static std::string format(sender_t sender, std::string message);;
static std::string HRESULTSTRING(HRESULT result);

typedef sinks::synchronous_sink< sinks::text_ostream_backend > text_sink;

static std::string CreateFormat()
{
    logger::add_common_attributes();
    logger::register_simple_formatter_factory< LEVEL, char >("Severity");
    return "[%TimeStamp%] [%ThreadID%] [%Severity%]: %Message%";
}

static void AddTerminalLogger(std::string format)
{
    auto sink = boost::make_shared<text_sink>();
    sink->locked_backend()->add_stream(boost::shared_ptr<std::ostream>(&std::cout, boost::null_deleter()));
    sink->locked_backend()->auto_flush(true);
    //sink->set_formatter( format );
    logger::core::get()->add_sink(sink);
}

static void AddFileLogger(std::string path, std::string format)
{
    logger::add_file_log
        (
        logger::keywords::file_name = path + "ManualTest_%Y-%m-%d_%H-%M-%S.%N.log",
        logger::keywords::rotation_size = 10 * 1024 * 1024,
        logger::keywords::time_based_rotation = sinks::file::rotation_at_time_point(0, 0, 0),
        logger::keywords::format = format
        );
}

static void SetLogLevel(LEVEL level)
{
    logger::core::get()->set_filter(logger::trivial::severity >= level);
}

void LogHelper::SetupLoggers(std::string path)
{
    std::string format = CreateFormat();
    AddFileLogger(path, format);
    AddTerminalLogger(format);
    SetLogLevel(LEVEL::trace);
}

I want to use my existing format string to set up my console logging as well. How can I reuse "[%TimeStamp%] [%ThreadID%] [%Severity%]: %Message%" so I do not repeat myself when I create my format expression?

Edit: To clarify: This is not valid as far as I know: sink->set_formatter(expr::format("[%TimeStamp%] [%ThreadID%] [%Severity%]: %Message%")); If I wanted to use set_formatter I would have to write an expression that does the same thing as this logger::keywords::format = "[%TimeStamp%] [%ThreadID%] [%Severity%]: %Message%". If I do so I would use one approach per logger (Terminal, File) to hopefully get the same formatting in both. Both loggers are a sink that is added to the core. So i assume the method logger::add_file_log uses something like set_formatter under the hood. I would like to use the capabilities that are built in somewhere that would allow me to apply the string "[%TimeStamp%] [%ThreadID%] [%Severity%]: %Message%" to a sink. I can not find the documentation though. When I look this topic up I do find how to use set_formatter but it always ends up in developing something different that gets the same result. I feel this introduces error potential since I would just repeat myself in the sense that I would rewrite the formatting I want in my logging just with slight variations.

Edit: Changed the source code to better reflect the question.

Make it a global constant or a #define? Or am I missing something? — AaronI
– AaronI, Commented Jan 21, 2016 at 17:36
Ah, i should refine my question, this is not about how to pass things as parameters. This is about how an expression is way more complicated than the logger keyword. I would like to use one way of doing this rather than maintaining two ways of doing the same thing. — Johannes
– Johannes, Commented Jan 21, 2016 at 21:50

Andrey Semashev · Accepted Answer · 2016-01-22 14:14:26Z

1

First, you can use add_console_log function similarly to how you use add_file_log in your code.

Second, both these functions use the formatter parser (the parse_formatter function) to convert the format string to the actual formatter you can supply to set_formatter. You can use this function directly to avoid parsing the string multiple times.

answered Jan 22, 2016 at 14:14

Andrey Semashev

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