Boost::Log and log numbering

Question

I've recently tried to add some logging via Boost log to a small application. However, using log rotation I can't for some reason get it to pick up the correct counter in the logs directory.

For example, if my Logs directory contains the files Log_000.log and Log_001.log I'd expect the logging to start with Log_002.log but it always starts again from 0.

I'm probably missing something but if anyone can spot something I'd be grateful. Here's my startup code:

void initLogging()
{
    boost::log::add_common_attributes();
    auto core = boost::log::core::get();

    core->add_global_attribute("UTCTimeStamp",boost::log::attributes::utc_clock());

    auto x = boost::log::add_file_log(
        boost::log::keywords::file_name             = "Log_%3N.log",
        boost::log::keywords::rotation_size         = 2 * 1024, // 2k
        boost::log::keywords::target                = "Logs",
        boost::log::keywords::min_free_space        = 30 * 1024 * 1024,
        boost::log::keywords::max_size              = 20 * 1024, // 20k
        boost::log::keywords::time_based_rotation   = boost::log::sinks::file::rotation_at_time_point(boost::gregorian::greg_day(31)),
        boost::log::keywords::scan_method           = boost::log::sinks::file::scan_matching,
        boost::log::keywords::format                = "%UTCTimeStamp% (%TimeStamp%) [%ThreadID%]: %Message%",
        boost::log::keywords::auto_flush            = true
        );

    auto d = x->locked_backend()->scan_for_files();
}

Many thanks

I have never used this library so I can't be sure this is correct, but looking at the [documentation](http://www.boost.org/libs/log/doc/html/log/detailed/sink_backends.html#log.detailed.sink_backends.text_file.managing_rotated_files) makes me think that you need to add something like `x->locked_backend()->set_file_collector(boost::log::sinks::file::make_collector(boost::log::keywords::target = "Logs"));` before your `scan_for_files` invocation. — llonesmiz, Jul 17 '15 at 14:12
I tried that earlier today in desperation, but it just gives me the same result :( Must be missing something — Dave F, Jul 17 '15 at 14:17

score 5 · Answer 1 · edited Jul 17 '15 at 16:27

Aha! It looks like if you use the add_file_log helper it automatically calls scan_for_files.

Calling it again causes the counter to be reset it seems, so I just removed my call to scan_for_files

Just popped this on as an answer in case it was driving anyone else mad!

Here's a working sample

Live On Coliru

You'll see that after it ran 10 times, Logs/ contains:

-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_080.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_081.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_082.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_083.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_084.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_085.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_086.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_087.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_088.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_089.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_090.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_091.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_092.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_093.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_094.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_095.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_096.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_097.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_098.log
-rw-r--r-- 1 2001 2000 998 Jul 17 16:26 Log_099.log

Code Listing

#define BOOST_LOG_DYN_LINK 1
#include <boost/log/core.hpp>
#include <boost/log/common.hpp>
#include <boost/log/attributes.hpp>
#include <boost/log/sinks.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/trivial.hpp>
#include <boost/log/utility/setup/common_attributes.hpp>
#include <boost/log/utility/setup/file.hpp>
#include <string>

void initLogging()
{
    boost::log::add_common_attributes();
    auto core = boost::log::core::get();

    core->add_global_attribute("UTCTimeStamp",boost::log::attributes::utc_clock());

    auto x = boost::log::add_file_log(
            boost::log::keywords::file_name             = "Log_%3N.log",
            boost::log::keywords::rotation_size         = 1 * 1024, // 1k
            boost::log::keywords::target                = "Logs",
            boost::log::keywords::min_free_space        = 30 * 1024 * 1024,
            boost::log::keywords::max_size              = 20 * 1024,
            boost::log::keywords::time_based_rotation   = boost::log::sinks::file::rotation_at_time_point(boost::gregorian::greg_day(31)),
            boost::log::keywords::scan_method           = boost::log::sinks::file::scan_matching,
            boost::log::keywords::format                = "%UTCTimeStamp% (%TimeStamp%) [%ThreadID%]: %Message%",
            boost::log::keywords::auto_flush            = true
        );

    //auto d = x->locked_backend()->scan_for_files();
}

int main()
{
    initLogging();
    for (int i = 0; i < 20; ++i) {
        BOOST_LOG_TRIVIAL(trace) << "Let's go shopping " << std::string(400, '*');
    }
}

Wow. That's is most helpful. Mind if I make the sample self-contained? — sehe, Jul 17 '15 at 15:51
Mmm. I don't see how it improved: http://coliru.stacked-crooked.com/a/1abcce12f115d60b (still shows starting from `000` again and suffixing `00000`) — sehe, Jul 17 '15 at 15:56
Hmm. I notice you have "scan_all" rather than "scan_matching" - is that possibly it? — Dave F, Jul 17 '15 at 16:19

Boost::Log and log numbering

1 Answers1

Code Listing

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