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FairLogger

Lightweight and fast C++ Logging Library

example output

Branch Build Status
master build status master branch
dev build status dev branch

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

FairLogger bundles a version of the fmt library. You can override this with your own fmt installation via the -DUSE_EXTERNAL_FMT=ON and -DFMT_ROOT=/fmt/location CMake switches.

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.

If FairLogger is built with -DUSE_BOOST_PRETTY_FUNCTION=ON and/or -DUSE_EXTERNAL_FMT=ON, your project needs to find the external dependencies, too, e.g.

find_package(FairLogger)
foreach(dep IN LISTS FairLogger_PACKAGE_DEPENDENCIES)
  find_package(${dep} ${FairLogger_${dep}_VERSION})
endforeach()

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.
  • -DUSE_EXTERNAL_FMT=ON uses external fmt instead of the bundled one.

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. Additional macros

A number of additional logging macros are provided:

  • LOGV(severity, verbosity) Log the line with the provided verbosity, e.g. LOG(info, veryhigh) << "abcd";
  • LOGF(severity, ...) The arguments are given to fmt::printf, which formats the string using a printf syntax and the result is logged, e.g. LOGF(info, "Hello %s!", "world");
  • LOGP(severity, ...) The arguments are given to fmt::format, which formats the string using a Python-like syntax and the result is logged, e.g. LOGP(info, "Hello {}!", "world");
  • LOGN(severity) Logs an empty line, e.g. LOGN(info);
  • LOG_IF(severity, condition) Logs the line if the provided condition if true
  • LOGD(severity, file, line, f) Logs the line with the provided file, line and function parameters (only if the active verbosity allows it).

3. 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",
"trace",
"debug4",
"debug3",
"debug2",
"debug1",
"debug",
"detail",
"info",
"state",
"warn",
"important",
"alarm",
"error",
"fatal",

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

3.1 Compile-time severity switch

The minimum severity level can be configured at compile time via definition of FAIR_MIN_SEVERITY:

cmake -DFAIR_MIN_SEVERITY=warn ..

The above would only log severities equal to or above warn.

When FAIR_MIN_SEVERITY is not provided all severities are enabled.

4. 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, user1, user2, user3, user4, which translates to following output:

verylow:  message
low:      [severity] message
medium:   [HH:MM:SS][severity] message
high:     [process_name][HH:MM:SS][severity] message
veryhigh: [process_name][HH:MM:SS:µS][severity][file:line:function] message
user1:    [severity] message
user2:    [severity] message
user3:    [severity] message
user4:    [severity] 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]

4.1 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).

5. 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).

6. 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).

7. 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".

Naming conflicts?

By default, <fairlogger/Logger.h> defines unprefixed macros: LOG, LOGV, LOGF, LOGP, LOGN, LOGD, LOG_IF.

Define an option FAIR_NO_LOG* to prevent the above unprefixed macros to be defined, e.g.

#define FAIR_NO_LOG
#define FAIR_NO_LOGF
#include <fairlogger/Logger.h>

License

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

Copyright (C) 2017-2021 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH