Boost log rotating file - size exceeded - c++

Question

I try to log with Boost library 1.61, rotating file once size exceeded 5Ko. But, every time program runs, it begins from the first log file, exceeding max size !
That is, it appends text to flog000.txt, then to flog001.txt.
But the desired behaviour was: append to the last file (flog002.txt) then continue with flog003.txt...
Here is my code:
#include <boost/log/common.hpp>
#include <boost/log/sinks/text_ostream_backend.hpp>
#include <boost/log/core.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <boost/log/sources/logger.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
void init()
{
boost::log::add_file_log
(
boost::log::keywords::file_name = "flog%3N.txt",
boost::log::keywords::open_mode = std::ios_base::app,
boost::log::keywords::rotation_size = 5 * 1024,
boost::log::keywords::auto_flush = true
);
}
int main()
{
init();
boost::log::sources::logger lg;
boost::log::add_common_attributes();
for (int i(0); i < 1000; ++i)
{
BOOST_LOG(lg) << "Hello : " << i << std::endl;
}
return 0;
}

Answer 1

"There's no file collecting" - this is at least a part of the problem.
It does seem impossible to have scanning and append to an existing as well.
However, if you do scanning, you can at least prevent extra log messages from being wrongly appended to the older log files:
Live On Coliru
#include <boost/log/common.hpp>
#include <boost/log/core.hpp>
#include <boost/log/sinks/text_ostream_backend.hpp>
#include <boost/log/sources/logger.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/utility/setup/file.hpp>
void init() {
auto s = boost::log::add_file_log(
boost::log::keywords::file_name = "flog%3N.txt",
boost::log::keywords::open_mode = std::ios_base::app,
boost::log::keywords::rotation_size = 5 * 1024,
boost::log::keywords::auto_flush = true
);
auto be = s->locked_backend();
be->set_file_collector(boost::log::sinks::file::make_collector(
boost::log::keywords::target = "./", // log file & target have same dir
boost::log::keywords::max_size = 50 * 1024,
boost::log::keywords::min_free_space = 100000
));
be->scan_for_files(boost::log::sinks::file::scan_method::scan_matching, true);
}
int main() {
init();
boost::log::sources::logger lg;
boost::log::add_common_attributes();
for (int i(0); i < 1000; ++i) {
BOOST_LOG(lg) << "Hello : " << i << std::endl;
}
}
After one run:
-rw-rw-r-- 1 sehe sehe 5116 jun 6 00:27 flog000.txt
-rw-rw-r-- 1 sehe sehe 5109 jun 6 00:27 flog001.txt
-rw-rw-r-- 1 sehe sehe 2665 jun 6 00:27 flog002.txt
After two runs:
-rw-rw-r-- 1 sehe sehe 5116 jun 6 00:27 flog003.txt
-rw-rw-r-- 1 sehe sehe 5109 jun 6 00:27 flog004.txt
-rw-rw-r-- 1 sehe sehe 2665 jun 6 00:27 flog005.txt
After three runs:
-rw-rw-r-- 1 sehe sehe 5116 jun 6 00:28 flog006.txt
-rw-rw-r-- 1 sehe sehe 5109 jun 6 00:28 flog007.txt
-rw-rw-r-- 1 sehe sehe 2665 jun 6 00:28 flog008.txt