FairLogger

Lightweight and fast C++ Logging Library

Branch	Build Status
master
dev

Installation

git clone https://github.com/FairRootGroup/FairLogger
mkdir FairLogger_build && cd FairLogger_build
cmake -DCMAKE_INSTALL_PREFIX=./FairLogger_install ../FairLogger
cmake --build . --target install

Usage

In your CMakeLists.txt:

find_package(FairLogger)

If FairLogger is not installed in system directories, you can hint the installation location:

set(CMAKE_PREFIX_PATH /path/to/FairLogger/installation ${CMAKE_PREFIX_PATH})
find_package(FairLogger)

find_package(FairLogger) will define an imported target FairLogger::FairLogger.

CMake options

On command line:

• -DDISABLE_COLOR=ON disables coloured console output.
• -DBUILD_TESTING=OFF disables building of unit tests.
• -DUSE_BOOST_PRETTY_FUNCTION=ON enables usage of BOOST_PRETTY_FUNCTION macro.

Documentation

1. General

All log calls go through the provided LOG(severity) macro. Output through this macro is thread-safe. Logging is done to cout, file output and/or custom sinks.

2. Severity

The log severity is controlled via:

fair::Logger::SetConsoleSeverity("<severity level>");
// and/or
fair::Logger::SetFileSeverity("<severity level>");
// and/or
fair::Logger::SetCustomSeverity("<customSinkName>", "<severity level>");

where severity level is one of the following:

"nolog",
"fatal",
"error",
"warn",
"state",
"info",
"debug",
"debug1",
"debug2",
"debug3",
"debug4",
"trace",

Logger will log the chosen severity and all above it (except "nolog", which deactivates logging for that sink completely). Fatal severity is always logged.

3. Verbosity

The log verbosity is controlled via:

fair::Logger::SetVerbosity("<verbosity level>");

it is same for all sinks, and is one of the following values: verylow, low, medium, high, veryhigh, which translates to following output:

verylow:  message
low:      [severity] message
medium:   [HH:MM:SS][severity] message
high:     [process name][HH:MM:SS:µS][severity] message
veryhigh: [process name][HH:MM:SS:µS][severity][file:line:function] message

When running a FairMQ device, the log severity can be simply provided via --verbosity <level> cmd option.

The user may customize the existing verbosities or any of user1, user2, user3, user4 verbosities via:

void fair::Logger::DefineVerbosity(fair::Verbosity, fair::VerbositySpec);
void fair::Logger::DefineVerbosity("<verbosity level>", fair::VerbositySpec);

The fair::Logger::VerbositySpec object can e.g. be created like this:

auto spec = fair::VerbositySpec::Make(VerbositySpec::Info::timestamp_s,
                                      VerbositySpec::Info::process_name);
// results in [HH:MM:SS][process name] message

Argument	Result
fair::VerbositySpec::Info::process_name	[process name]
fair::VerbositySpec::Info::timestamp_s	[HH:MM:SS]
fair::VerbositySpec::Info::timestamp_us	[HH:MM:SS:µS]
fair::VerbositySpec::Info::severity	[severity]
fair::VerbositySpec::Info::file	[file]
fair::VerbositySpec::Info::file_line	[file:line]
fair::VerbositySpec::Info::file_line_function	[file:line:function]

3.1 BOOST_PRETTY_FUNCTION support

By default, the veryhigh verbosity prints the function name from which the LOG macro was invoked. If you desire a more verbose function signature including the full namespace, return value and function arguments, you can enable support for BOOST_PRETTY_FUNCTION

• globally by compiling FairLogger with the CMake option -DUSE_BOOST_PRETTY_FUNCTION=ON, or
• per translation unit by defining FAIRLOGGER_USE_BOOST_PRETTY_FUNCTION before including the FairLogger header, e.g.

#define FAIRLOGGER_USE_BOOST_PRETTY_FUNCTION
#include <Logger.h>

In the latter case, the user needs to take care of adding the boost include path to the compiler search path manually (e.g. -I/path/to/boost/include).

4. Color

Colored output on console can be activated with:

Logger::SetConsoleColor(true);

When running a FairMQ device, the log color (console) can be simply provided via --color <true/false> cmd option (default is true).

5. File output

Output to file can be enabled via:

Logger::InitFileSink("<severity level>", "test_log", true);

which will add output to "test_log" filename (if third parameter is true it will add timestamp to the file name) with <severity level> severity.

When running a FairMQ device, the log file can be simply provided via --log-to-file <filename_prefix> cmd option (this will also turn off console output).

5.5 Custom sinks

Custom sinks can be added via Logger::AddCustomSink("sink name", "<severity>", callback) method.

Here is an example adding a custom sink for all severities ("trace" and above). It has access to the log content and meta data. Custom log calls are also thread-safe.

    Logger::AddCustomSink("MyCustomSink", "trace", [](const string& content, const LogMetaData& metadata)
    {
        cout << "content: " << content << endl;

        cout << "available metadata: " << endl;
        cout << "std::time_t timestamp: " << metadata.timestamp << endl;
        cout << "std::chrono::microseconds us: " << metadata.us.count() << endl;
        cout << "std::string process_name: " << metadata.process_name << endl;
        cout << "std::string file: " << metadata.file << endl;
        cout << "std::string line: " << metadata.line << endl;
        cout << "std::string func: " << metadata.func << endl;
        cout << "std::string severity_name: " << metadata.severity_name << endl;
        cout << "fair::Severity severity: " << static_cast<int>(metadata.severity) << endl;
    });

If only output from custom sinks is desirable, console/file sinks must be deactivated by setting their severity to "nolog".

License

GNU Lesser General Public Licence (LGPL) version 3, see LICENSE.

Copyright (C) 2017-2018 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH