FairLogger/README.md
Dennis Klein 3e1de0a17b Support user-defined verbosity formats
* Add `fair::Logger::DefineVerbosity(...)` API
* Add documentation to README
* Optionally support `BOOST_PRETTY_FUNCTION`
2019-01-02 09:18:30 +01:00

188 lines
6.4 KiB
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# FairLogger
Lightweight and fast C++ Logging Library
![example output](example.png)
| Branch | Build Status |
| :---: | :--- |
| `master` | ![build status master branch](https://alfa-ci.gsi.de/buildStatus/icon?job=FairRootGroup/FairLogger/master) |
| `dev` | ![build status dev branch](https://alfa-ci.gsi.de/buildStatus/icon?job=FairRootGroup/FairLogger/dev) |
## Installation
```bash
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`:
```cmake
find_package(FairLogger)
```
If FairLogger is not installed in system directories, you can hint the installation location:
```cmake
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:
```C++
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:
```C++
"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:
```C++
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:
```C++
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:
```C++
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.
```C++
#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:
```C++
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:
```C++
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.
```C++
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](LICENSE).
Copyright (C) 2017-2018 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH