boost log file not written to

Question

I've been struggling with boost log for a while now - I got their simple example writing to a log file (http://boost-log.sourceforge.net/libs/log/example/doc/tutorial_file.cpp). However, when I try to copy that code into a 'Logger' class, I can't get it to write to the log file. I can see the file default.log get created, but there is nothing in it.

I'm on debian 7 64bit. Everything compiles fine - compile line is:

g++ -o build/Logger.o -c -std=c++11 -Wall -g -O0 -DBOOST_LOG_DYN_LINK -DDEBUG src/Logger.cpp
g++ -o build/logtest build/Logger.o -lboost_log -lboost_log_setup -lboost_date_time -lboost_thread -lboost_wave -lboost_regex -lboost_program_options

Here's my code:

Logger.cpp

/*
 * Logger.cpp
 *
 *  Created on: 2011-01-17
 *      Author: jarrett
 */

#include "Logger.h"

namespace logging = boost::log;
namespace sinks = boost::log::sinks;
namespace src = boost::log::sources;
namespace expr = boost::log::expressions;
namespace attrs = boost::log::attributes;
namespace keywords = boost::log::keywords;

namespace dhlogging {

Logger::Logger(std::string fileName)
{
    initialize(fileName);
}

Logger::Logger(Logger const&)
{
}

Logger::~Logger()
{

}

Logger* Logger::logger_ = nullptr;
Logger* Logger::getInstance(std::string logFile)
{
    if ( Logger::logger_ == nullptr ) {
        logging::add_file_log( logFile );

        logging::core::get()->set_filter
        (
            logging::trivial::severity >= logging::trivial::info
        );

        logging::add_common_attributes();
        Logger::logger_ = new Logger(logFile);
    }

    return Logger::logger_;
}

void Logger::initialize(std::string fileName)
{   
    BOOST_LOG(log_) << "Hello, World!";
    BOOST_LOG_SEV(log_, info) << "Hello, World2!";
}

void Logger::logInfo(std::string message)
{
    BOOST_LOG_SEV(log_, info) << message;
}

void Logger::logDebug(std::string message)
{
    BOOST_LOG_SEV(log_, debug) << message;
}

void Logger::logWarn(std::string message)
{
    BOOST_LOG_SEV(log_, warning) << message;
}

void Logger::logError(std::string message)
{
    BOOST_LOG_SEV(log_, error) << message;
}

void Logger::logFatal(std::string message)
{
    BOOST_LOG_SEV(log_, fatal) << message;
}

}

int main(int, char*[])
{
    logging::add_common_attributes();

    using namespace logging::trivial;

    dhlogging::Logger::getInstance()->logInfo("himom");

    return 0;
}

Logger.h

/*
 * Logger.h
 *
 *  Created on: 2011-01-17
 *      Author: jarrett
 */

#ifndef LOGGER_H_
#define LOGGER_H_

#include <map>
#include <boost/log/core.hpp>
#include <boost/log/trivial.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/sinks/text_file_backend.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/sources/severity_logger.hpp>
#include <boost/log/sources/record_ostream.hpp>

namespace logging = boost::log;
namespace sinks = boost::log::sinks;
namespace src = boost::log::sources;
namespace expr = boost::log::expressions;
namespace attrs = boost::log::attributes;
namespace keywords = boost::log::keywords;

using namespace logging::trivial;

namespace dhlogging {
class Logger {

public:
    static Logger* getInstance(std::string logFile = "default.log");

    void logInfo(std::string message);
    void logDebug(std::string message);
    void logWarn(std::string message);
    void logError(std::string message);
    void logFatal(std::string message);


private:
    Logger(std::string fileName);
    Logger(Logger const&);
    Logger& operator=(Logger const&);
    virtual ~Logger();

    void initialize(std::string fileName);

    src::severity_logger< severity_level > log_;

    static Logger* logger_; // singleton instance
};
}
#endif /* LOGGER_H_ */

Answer 1

you need to this attribute when creating the file log

keywords::auto_flush = true 

that way log entrys get written immediately. by default, the file logger seems to write to file when it goes out of scope, or at some other mysterious point, the documentation doesn´t mention anything about