Logging sinks to be used with G3log

Each sink will have its own LICENSE file. Make sure to understand what the sink provides before you use it.

Adapted from vrecan/g2log-dev https://bitbucket.org/vrecan/g2log-dev Rotation of logs. The license is public domain, a.k.a the UNLICENSE. See details at the sink location.

This sink directs g3log messages into the unix syslog system. Settings with syslog-ng/rsyslog can then be used to sort these to separate files, forward them to a remote machine, rotate log files when they get large, etc.

The mapping between G3 and syslog concepts is as follows:

• The log level is mapped to a syslog level by default as

    1. G3LOG_DEBUG -> LOG_DEBUG
    2. INFO -> LOG_INFO
    3. (INFO.value + WARNING.value )/2 -> LOG_NOTICE [there's no notice level in G3)
    4. WARNING -> LOG_WARNING
    5. FATAL -> LOG_CRIT
  

• If you log to a custom level between these, the level will be "rounded down". For example, a log record with a level of (FATAL.value-1) will get a syslog level of WARNING

• You can adjust this behavior through the setLevel() function.

• The "identity" of your process can be changed via the constructor's argument or the setIdentity() method. This is usually the primary value for filtering.

• The syslog "facility code" of the messages is set to LOG_USER by default, but use setFacility() to change.

• By default, nothing is written to the console when you log. You can have messages also echoed to stderr by calling echoToStderr()

• On the first log (only) of your program, a special banner header can be written. Use setLogHeader() to enable this. Use this to distinguish between runs in the logs.

A word of caution: syslog will timestamp each record itself, but with the time that the syslog daemon recieved the message, not the time it was created. You can include the creation time in your record via the formatter. The setFormatter() function accepts a function pointer of the type std::string (*) (const LogMessage&) to handle the formatting.

An example program is at sink_syslog/example/main.cpp.

The syslog sink should work out of the box on Linux systems without additional dependencies. It has not been tested on Cygwin.

This component license is public domain, a.k.a the UNLICENSE. See details at the sink location.

sink to allow logging through Windows TraceLogging For build instructions please see tracelogging/README

Code snippet examples and a short description. These are not installed but can be used as helpful examples on how to create your custom sinks

For more information please look at the Readme and API documentation i.e. https://github.com/KjellKod/g3log For detailed sink usage please see the header files and tests in his repository. They are written so that The sink usage should be clear.

g3log
G3sinks requires g3log to be installed. The g3log install location has to be specified during the cmake build step. In the example below the g3log installation location is /usr/local with libraries in '/usr/local/lib' and 'headers in '/usr/local/include' The given argument for the location would then be : 'cmake -DCMAKE_PREFIX_PATH=/usr/local/'

ZLIB
The ZLIB library must be installed for the logrotate to be able to compress the old log files in Ubuntu it can be installed with sudo apt-get install zlib1g-dev. Please see your specific platform for details or go to the zlib page

cd g3sinks
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_PREFIX_PATH=/usr/local/ -DBUILD_TEST=ON ..
make -j

cd .. // out to g3sinks root directory
./scripts/buildAndRunTests.sh

From the build directory after a successful cmake & make

// any of these should work 
./test/test_testlogrotate 
make test 
ctest 
ctest -V

sudo make install

Alternative on Debian systems

make package
sudo dpkg -i g3LogRotate-<package_version>Linux.deb

Example usage where a logrotate sink is added. The logrotate limit is changed from the default to instead be 10MB. The limit is changed by calling the sink handler which passes the function call through to the actual logrotate sink object.

// main.cpp
#include <g3log/g3log.hpp>
#include <g3log/logworker.h>
#include <g3sinks/LogRotate.h>
#include <memory>

int main(int argc, char**argv) {
   using namespace g3;
   std::unique_ptr<LogWorker> logworker{ LogWorker::createLogWorker() };
   auto sinkHandle = logworker->addSink(std::make_unique<LogRotate>(),
                                          &LogRotate::save);
   
   // initialize the logger before it can receive LOG calls
   initializeLogging(logworker.get());            
            
   // You can call in a thread safe manner public functions on the logrotate sink
   // The call is asynchronously executed on your custom sink.
   const int k10MBInBytes = 10 * 1024 * 1024;
   std::future<void> received = sinkHandle->call(&LogRotate::setMaxLogSize, k10MBInBytes);
   // You can manually trigger a rotate of the log
   std::future<bool> rotate = sinkHandle->call(&LogRotate::rotateLog);
   // Run the main part of the application. This can be anything of course, in this example
   // we'll call it "RunApplication". Once this call exits we are in shutdown mode
   RunApplication();

   // If the LogWorker is initialized then at scope exit the g3::shutDownLogging() will be 
   // called automatically. 
   //  
   // This is important since it protects from LOG calls from static or other entities that will go out of
   // scope at a later time. 
   //
   // It can also be called manually if for some reason your setup is different then the one highlighted in
   // this example
   g3::shutDownLogging();
}

G3sinks has a couple of different approaches for verifying pull requests. At some point they might be consolidated but right now the CI is organized as follows.

1. appveyor Windows CI --> g3sinks/appveyor.yml
2. github actions --> g3sinks/.github/workflows/cmake_build_run.yml
calls a script that does all heavy lifting, leaving the github actions file to mostly deal with the 
environment bootstrapping. The test result is verbose. 

Future improvements could here be to:
1. Use Windows/OSX/Linux all within github actions. 
2. Create and use a base image that is already bootstrapped. 

These sinks for g3log are available for free and all of its source code is public domain. A great way of saying thanks is to send a donation. It would go a long way not only to show your support but also to boost continued development.

• $5 for a cup of coffee
• $10 for pizza
• $25 for a late evening coding with takeout Cheers

Kjell