Traditional log function supports log level, which is similar to boost::log::trivial::severity_level.
void simple_log(int log_level, char* fmt, ...);
The problem with traditional log function is that all modules are using the same log level, when debug level is enabled, there are too many log messages which may potentially change program behavior.
with boot log library it is easier to control log level per module.
BOOST_LOG_INLINE_GLOBAL_LOGGER_CTOR_ARGS(mylog1, my_logger_mt, (boost::log::keywords::channel = "mylog1"))
BOOST_LOG_INLINE_GLOBAL_LOGGER_CTOR_ARGS(mylog2, my_logger_mt, (boost::log::keywords::channel = "mylog2"))
module1 uses mylog1 to output message; module2 uses mylog2 to output message.
BOOST_LOG_SEV(mylog2::get(), boost::log::trivial::warning) << "from mylog2 " << boost::posix_time::second_clock::local_time();
BOOST_LOG_SEV(mylog1::get(), boost::log::trivial::info) << "from mylog1 " << boost::posix_time::second_clock::local_time();
Complete source code.
#include <cstddef>
#include <string>
#include <fstream>
#include <iomanip>
#include <boost/utility/empty_deleter.hpp>
#include <boost/log/core.hpp>
#include <boost/log/trivial.hpp>
#include <boost/log/sinks.hpp>
#include <boost/log/support/date_time.hpp>
#include <boost/log/common.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/attributes.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/utility/setup/formatter_parser.hpp>
#include <boost/log/sources/severity_logger.hpp>
#include <boost/log/sources/severity_feature.hpp>
#include <boost/log/sources/channel_feature.hpp>
#include <boost/log/sources/channel_logger.hpp>
#include <boost/log/sources/logger.hpp>
#include <boost/log/sources/record_ostream.hpp>
#include <boost/log/sources/global_logger_storage.hpp>
#include <boost/thread/thread.hpp>
#include <sys/types.h>
namespace logging = boost::log;
namespace sinks = boost::log::sinks;
typedef boost::log::sources::severity_channel_logger_mt<
logging::trivial::severity_level, // the type of the severity level
std::string // the type of the channel name
> my_logger_mt;
BOOST_LOG_INLINE_GLOBAL_LOGGER_CTOR_ARGS(mylog1, my_logger_mt, (boost::log::keywords::channel = "mylog1"))
BOOST_LOG_INLINE_GLOBAL_LOGGER_CTOR_ARGS(mylog2, my_logger_mt, (boost::log::keywords::channel = "mylog2"))
BOOST_LOG_ATTRIBUTE_KEYWORD(thread_id, "ThreadID", logging::attributes::current_thread_id::value_type)
void init_logging()
{
boost::shared_ptr< logging::core > core = logging::core::get();
boost::shared_ptr< sinks::text_ostream_backend > backend =
boost::make_shared< sinks::text_ostream_backend >();
backend->add_stream(boost::shared_ptr< std::ostream >(&std::clog, boost::empty_deleter()));
backend->add_stream(boost::shared_ptr< std::ostream >(new std::ofstream("sample.log", std::ofstream::app)));
backend->auto_flush(true);
typedef sinks::synchronous_sink< sinks::text_ostream_backend > sink_t;
boost::shared_ptr< sink_t > sink(new sink_t(backend));
sink->set_formatter
(
boost::log::expressions::stream
<< boost::log::expressions::format_date_time< boost::posix_time::ptime >("TimeStamp", "%Y%m%d %H:%M:%S")
<< " "<< boost::log::expressions::attr<boost::log::attributes::current_thread_id::value_type>("ThreadID")
<< " "<< boost::log::expressions::attr< std::string >("Channel")<< " "
<< ": <" << boost::log::trivial::severity
<< "> " << boost::log::expressions::smessage
);
core->add_sink(sink);
core->set_filter
(
(boost::log::expressions::attr< std::string >("Channel") == "mylog1" &&
logging::trivial::severity >= logging::trivial::info) ||
(boost::log::expressions::attr< std::string >("Channel") == "mylog2" &&
logging::trivial::severity >= logging::trivial::trace) ||
logging::trivial::severity >= logging::trivial::error ||
!boost::log::expressions::has_attr("Channel")
);
boost::log::add_common_attributes();
logging::core::get()->add_global_attribute("ThreadID",logging::attributes::current_thread_id());
}
struct callable
{
callable()
{
BOOST_LOG_SEV(mylog1::get(), boost::log::trivial::info) << __FUNCTION__;
}
callable(const callable& aaa)
{
BOOST_LOG_SEV(mylog1::get(), boost::log::trivial::info) << __FUNCTION__ << " copy ctor.";
}
~callable()
{
BOOST_LOG_SEV(mylog1::get(), boost::log::trivial::info) << __FUNCTION__;
}
void operator()()
{
BOOST_LOG_SEV(mylog1::get(), boost::log::trivial::info) << __FUNCTION__ << " thread id is " << std::hex<< (unsigned int)pthread_self();
}
};
boost::thread copies_are_safe()
{
callable x;
return boost::thread(x);
}
int main(int argc, char* argv[]) {
init_logging();
std::cout << "Each logger use its own channel, check sample.log" << std::endl;
BOOST_LOG_TRIVIAL(trace) << "A trace severity message";
BOOST_LOG_TRIVIAL(debug) << "A debug severity message";
BOOST_LOG_TRIVIAL(info) << argv[0] << " start at "
<< boost::posix_time::second_clock::local_time()
<< ", program was built at "<<__DATE__ <<" " <<__TIME__ <<" by gcc "<<__VERSION__;
BOOST_LOG_TRIVIAL(error) << "An error severity message";
BOOST_LOG_TRIVIAL(fatal) << "A fatal severity message";
BOOST_LOG_SEV(mylog2::get(), boost::log::trivial::warning) << "from mylog2 " << boost::posix_time::second_clock::local_time();
BOOST_LOG_SEV(mylog1::get(), boost::log::trivial::info) << "from mylog1 " << boost::posix_time::second_clock::local_time();
BOOST_LOG_SEV(mylog1::get(), boost::log::trivial::trace) << "no trace from mylog1";
boost::thread mythread=copies_are_safe();
mythread.join();
return 0;
}
/*
[onega@workstation Debug]$ LD_LIBRARY_PATH=~/boost_1_55_0/lib:~/gcc-4.8.2/lib ./multilog
Each logger use its own channel, check sample.log
20140418 17:21:29 0xb7f016d0 : <trace> A trace severity message
20140418 17:21:29 0xb7f016d0 : <debug> A debug severity message
20140418 17:21:29 0xb7f016d0 : <info> ./multilog start at 2014-Apr-18 17:21:29, program was built at Apr 18 2014 17:21:19 by gcc 4.8.2
20140418 17:21:29 0xb7f016d0 : <error> An error severity message
20140418 17:21:29 0xb7f016d0 : <fatal> A fatal severity message
20140418 17:21:29 0xb7f016d0 mylog2 : <warning> from mylog2 2014-Apr-18 17:21:29
20140418 17:21:29 0xb7f016d0 mylog1 : <info> from mylog1 2014-Apr-18 17:21:29
20140418 17:21:29 0xb7f016d0 mylog1 : <info> callable
20140418 17:21:29 0xb7f016d0 mylog1 : <info> callable copy ctor.
20140418 17:21:29 0xb7f016d0 mylog1 : <info> callable copy ctor.
20140418 17:21:29 0xb7f016d0 mylog1 : <info> callable copy ctor.
20140418 17:21:29 0xb7f016d0 mylog1 : <info> callable copy ctor.
20140418 17:21:29 0xb7f016d0 mylog1 : <info> ~callable
20140418 17:21:29 0xb7f016d0 mylog1 : <info> ~callable
20140418 17:21:29 0xb7f016d0 mylog1 : <info> ~callable
20140418 17:21:29 0xb7f016d0 mylog1 : <info> ~callable
20140418 17:21:29 0xb7f00b90 mylog1 : <info> operator() thread id is b7f00b90
20140418 17:21:29 0xb7f016d0 mylog1 : <info> ~callable
Invoking: GCC C++ Compiler
~/gcc-4.8.2/bin/g++ -DBOOST_ALL_DYN_LINK -I/home/onega/boost_1_55_0/include -O0 -g3 -c -fmessage-length=0 -Wunused-variable -MMD -MP -MF"src/multilog.d" -MT"src/multilog.d" -o "src/multilog.o" "../src/multilog.cpp"
Invoking: GCC C++ Linker
~/gcc-4.8.2/bin/g++ -L/home/onega/boost_1_55_0/lib -o "multilog" ./src/multilog.o -lboost_log -lboost_thread -lboost_chrono -lboost_filesystem -lboost_date_time -lboost_system
Invoking: Cygwin C++ Linker
g++ -L"C:\Users\onega.zhang\workspace\boost_1_55_0\stage\lib" -o "multilog.exe" ./src/multilog.o -lboost_log-mt -lboost_thread-mt -lboost_date_time -lboost_filesystem-mt -lboost_system-mt
Invoking: Cygwin C++ Compiler
g++ -DBOOST_ALL_DYN_LINK -I"C:\Users\onega.zhang\workspace\boost_1_55_0" -O0 -g3 -c -fmessage-length=0 -Wunused-local-typedefs -Wunused-value -MMD -MP -MF"src/multilog.d" -MT"src/multilog.d" -o "src/multilog.o" "../src/multilog.cpp"
onega.zhang@R9REZAF /cygdrive/c/Users/onega.zhang/workspace/boost_1_55_0/stage/lib
$ /cygdrive/c/Users/onega.zhang/workspace/multilog/Debug/multilog.exe
Each logger use its own channel, check sample.log
A trace severity message
A debug severity message
/cygdrive/c/Users/onega.zhang/workspace/multilog/Debug/multilog start at 2014-Apr-17 16:01:30
A warning severity message
An error severity message
A fatal severity message
from mylog2
from mylog1 2014-Apr-17 16:01:30
*/
