Logging¶
The Acts logging facility supports several severity levels which allow you
to control the amount of information displayed at run-time. Logger objects
can easily be created using the Acts::getDefaultLogger()
function which
should be sufficient to get you started. In case you need more customized
debug output, you can make use of the output decorators defined in
Acts::Logging
or even write your own implementation of
Acts::Logging::OutputDecorator
. In order to add debug messages to your program, you should use the provided macros for the different severity levels:
ACTS_VERBOSE(...);
ACTS_DEBUG(...);
ACTS_INFO(...);
ACTS_WARNING(...);
ACTS_ERROR(...);
ACTS_FATAL(...);
All of these macros require that a function logger()
returning a
Acts::Logger
object is available in the scope in which the macros are
used. Inside classes containing an Acts::Logger
object as member
variable, this could be achieved by providing a private class method called
logger()
(for an example see e.g.
Acts::CylinderVolumeBuilder::logger()
). Inside free functions or member
methods with local logger objects, the same effect can be achieved by using the
macro ACTS_LOCAL_LOGGER(...)
which is provided for your convenience.
Code example illustrating the usage:
#include <fstream>
#include <memory>
#include "Acts/Utilities/Logger.hpp"
void myFunction() {
// open the logfile
std::ofstream logfile("log.txt");
// setup a logger instance for >= INFO messages, streaming into the log file
// make sure you do NOT call the variable 'logger'
std::unique_ptr<const Acts::Logger> myLogger
= Acts::getDefaultLogger("MyLogger", Acts::Logging::INFO, &logfile);
// make sure the Acts debug macros can work with your logger
ACTS_LOCAL_LOGGER(myLogger);
ACTS_VERBOSE("This message will not appear in the logfile.");
ACTS_INFO("But this one will: Hello World!");
// do not forget to close the logfile
logfile.close();
}
In case you are using Acts in another framework which comes with its own logging facility (e.g. Gaudi) you can pipe the logging output from Acts tools and algorithms to your framework’s logging system by supplying different implementations of:
Acts::Logging::OutputFilterPolicy
(for mapping logging levels)Acts::Logging::OutputPrintPolicy
(for passing the Acts outputto your internal logging system)
Since Acts makes extensive use of Acts::getDefaultLogger()
to provide
sufficient information for debugging, you would need to provide a modified
implementation of this function (using your output filter and printing policies)
to also pipe this output to your framework. Changing the implementation of an
already defined function is a non-trivial task in C++. We recommend the
following approach using the possibility to inject custom code by pre-loading
shared libraries with LD_PRELOAD
. You need to provide an appropriate
implementation for a function of the following signature into a separate source
file and compile it in a shared library
namespace Acts {
std::unique_ptr<const Logger> getDefaultLogger(const std::string&,
const Logging::Level&,
std::ostream*);
}
Then you can run your executable, which uses Acts tools and algorithms, in the following way (tested under Unix)
LD_PRELOAD=<YOUR_SHARED_LIBRARY> path/to/your/exectuable
For an example have a look at CustomDefaultLogger.cpp which you can use as follows:
cd <ACTS/INSTALL/DIRECTORY>
source bin/setup.sh
LD_PRELOAD=lib/libActsCustomLogger.so bin/Examples/ActsGenericDetector