如何在boost log 2.0中设置std :: ios_base标志,如std :: left？

Question

我有一个广泛使用boost log 2.0的应用程序.现在,我想设置一些默认的标志为应用程序一样std::setprecision(std::numeric_limits<double>::digits10 + 1),std::scientific和std::left.但是我该怎么做？一种方法是在我的main函数的最开始创建一个记录器并创建一个虚拟日志消息.这将永久设置所需的标志.但有没有更好的方法来做到这一点？

编辑回复:"OP应显示实际代码."

我有一个全局的Logging单例,叫做L:

class L{
public:
  enum severity_level
  {
      dddebug,
      ddebug,
      debug,
      control,
      iiinfo,
      iinfo,
      info,
      result,
      warning,
      error,
      critical
  };

  typedef boost::log::sources::severity_channel_logger<
      severity_level, // the type of the severity level
      std::string // the type of the channel name
  > logger_t;
  typedef boost::log::sinks::synchronous_sink< boost::log::sinks::text_ostream_backend > text_sink;
  boost::shared_ptr< text_sink > sink_;

  static L& get();
  static boost::shared_ptr<text_sink> sink();
  static double t0();
  static double tElapsed();
private:
  L();
  double t0_p;
  static std::string tElapsedFormat();

  L(const L&) = delete;
  void operator=(const L&) = delete;
};

它提供了日志记录接收器,严重性级别,并利用MPI方法在MPI节点之间进行同步计时.类成员的实现如下:

#include "log.h"

#include <iomanip>
#include <limits>
#include <fstream>
#include <boost/log/attributes/function.hpp>
#include <boost/smart_ptr/shared_ptr.hpp>
#include <boost/smart_ptr/make_shared_object.hpp>
#include <boost/log/core.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/sources/severity_channel_logger.hpp>
#include <boost/log/sinks/sync_frontend.hpp>
#include <boost/log/sinks/text_ostream_backend.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>


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

#include "mpiwrap.h"
#include <mpi.h>

BOOST_LOG_ATTRIBUTE_KEYWORD(t, "Time", std::string)
BOOST_LOG_ATTRIBUTE_KEYWORD(rank, "Rank", int)
BOOST_LOG_ATTRIBUTE_KEYWORD(channel, "Channel", std::string)
BOOST_LOG_ATTRIBUTE_KEYWORD(severity, "Severity", L::severity_level)

L::L():
  sink_(boost::make_shared< text_sink >()),
  t0_p(MPI_Wtime())
{

  sink_->locked_backend()->add_stream(
    boost::make_shared< std::ofstream >("log." + std::to_string(MpiWrap::getRank())));

  sink_->set_formatter
  (
    expr::stream
      << "< "
      << t << " "
      << "[p:" << rank << "] "
      << "[c:" << channel << "] "
      << "[s:" << severity << "] "
      << expr::smessage
  );

  logging::core::get()->add_sink(sink_);

  logging::core::get()->set_filter(

       (channel == "ChannelName1" && severity >= dddebug)
    || (channel == "ChannelName2" && severity >= info)
    || (channel == "ChannelName3" && severity >= result)

  );

  // Add attributes
  logging::core::get()->add_global_attribute("Time", attrs::make_function(&tElapsedFormat));
  logging::core::get()->add_global_attribute("Rank", attrs::constant<int>(MpiWrap::getRank()));
}

L& L::get(){
  static L instance;
  return instance;
}

boost::shared_ptr<L::text_sink> L::sink(){
  return get().sink_;
}

double L::t0(){
  return get().t0_p;
}

double L::tElapsed(){
  return MPI_Wtime() - t0();
}

std::string L::tElapsedFormat(){
  std::stringstream ss;
  const int prec = std::numeric_limits<double>::digits10;
  ss << std::setw(prec + 2 + 6) << std::left << std::setprecision(prec) << tElapsed();
  return ss.str();
}

std::ostream& operator<< (std::ostream& strm, L::severity_level level)
{
    static const char* strings[] =
    {
        "DBG3",
        "DBG2",
        "DBG1",
        "CTRL",
        "INF3",
        "INF2",
        "INF1",
        "RSLT",
        "WARN",
        "ERRR",
        "CRIT"
    };

    if (static_cast< std::size_t >(level) < sizeof(strings) / sizeof(*strings))
        strm << strings[level];
    else
        strm << static_cast< int >(level);

    return strm;
}

现在用于:我的类通常有一个静态logger_t(typedef for boost::log::sources::severity_channel_logger<severity_level, std::string>)成员

class A {
public:
    logger_t logger;
    //other stuff here
    void function_which_does_logging();
};

L::logger_t A::logger(boost::log::keywords::channel = "ClassA");

void A::function_which_does_logging(){
    //do non logging related stuff
    BOOST_LOG_SEV(logger, L::result) << "the error is: " << 0.1234567890;
    //do non logging related stuff
}

我目前解决问题的方法是在我的程序开头添加一个日志语句

int main(){
    L::logger_t logger(boost::log::keywords::channel = "init");
    BOOST_LOG_SEV(logger, L::critical) << "setting up logger" << std::scientific << std::setprecision(std::numeric_limits<double>::digits10 + 1);

    //do stuff
}

Answer 1

@rhashimoto对当前解决方案如何通过多线程/并发日志记录操作进行分解提出了一个很好的观点.我觉得最好的解决方案是定义自己的日志宏来替换BOOST_LOG_SEV包含流修饰符的日志宏,如下所示:

#define LOG_SCIENTIFIC(logger, sev) (BOOST_LOG_SEV(logger, sev) << std::scientific)

这可以仅用作替代品,BOOST_LOG_SEV其格式数字为科学.但是,通过代码并使用新的自定义宏替换每个日志记录操作可能会很痛苦.您也可以重新定义BOOST_LOG_SEV行为,而不是定义自己的宏.boost/log/sources/severity_feature.hpp定义BOOST_LOG_SEV如下:

//! An equivalent to BOOST_LOG_STREAM_SEV(logger, lvl)
#define BOOST_LOG_SEV(logger, lvl) BOOST_LOG_STREAM_SEV(logger, lvl)

因为BOOST_LOG_STREAM_SEV仍然是公共提升API的一部分,您应该能够安全地重新定义,BOOST_LOG_SEV如下所示:

#define BOOST_LOG_SEV(logger, lvl) (BOOST_LOG_STREAM_SEV(logger, lvl) << std::scientific)

只要在包含boost日志标题后定义了它,它就应该按照您的意愿执行.但是,我建议使用带有自定义名称的宏,以便其他人清楚您的代码正在做什么.