Rock

the Robot Construction Kit

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Base Logging

Introduction

Rock provides a logger that facilitates and unifies debugging of system libraries. The following section describes the functionality of the base logger and how to use it.

Adding the base logger to a library

When using the Rock CMake Macros, integration of the base logger is fairly easy. All you need to do is adding base-lib to your list of package config dependencies and include the header base/logging.h where logging is needed.

When using Rock CMake Macros add:

rock_library(test_library 
         DEPS_PKGCONFIG base-lib
         ...)

When not using Rock CMake Macros you have to set the logging namespace and embed the base library:

...
add_definitions(-DBASE_LOG_NAMESPACE=${PROJECT_NAME})

include(FindPkgConfig)

pkg_check_modules(BASE REQUIRED "base-lib")
include_directories(${BASE_INCLUDE_DIRS})
link_directories(${BASE_LIBRARY_DIRS})

add_library(your_library ...)
target_link_libraries(your_library ... ${BASE_LIBRARIES})

Using the logger

The logger allows you to log either in a printf-style or stream-style. For that purpose include it where needed and preferably in the .cpp files to avoid warnings about an undefined namespace for the logging.

#include<base/logging.h>

...
// printf-style logging
std::string information("test-logging happening here");
LOG_DEBUG("I provide you the following debug information: %s", 
    information.c_str());
LOG_INFO(...);
LOG_WARN(...);
LOG_ERROR(..);
LOG_FATAL(..);

// stream-style logging
LOG_DEBUG_S << information;
LOG_INFO_S << information;
...
LOG_FATAL << information;

The default output format of a log message looks like the following (without linebreak):

[20120120-11:58:00:577] [FATAL] - test_logger::A fatal error 
occurred (/tmp/test_logger/src/Main.cpp:10 - int main(int, char**))

Configuring the base logger

The logger can be configured at compile time to remove unwanted logging statement in a release version, and at runtime to control the verbosity level and logging format.

Compile-time

The following defines can be set to configure the logger at compile time:

BASE_LOG_NAMESPACE Setting the namespace to a unique string that allows you to filter the logging output, e.g. ROCK Macros automatically set it to the package name

BASE_LOG_DISABLE Deactivate all logging statements, e.g. for a realease binary.

BASE_LOG_xxx Compile only logs equal or higher than a certain level xxx into your binary, i.e. BASE_LOG_WARN disable all logs except for WARN, ERROR and FATAL Settings of log levels via environment variables with then only apply to the still activated levels.

BASE_LONG_NAMES Set this define in order to enforce a BASE_ prefix for the logging Macros, to avoid clashes with other libraries, i.e. BASE_LOG_DEBUG(…)

At run-time

The following enviroment variables can be used to control the behaviour of the logger:

BASE_LOG_LEVEL Set to one of DEBUG, INFO, WARN, ERROR or FATAL to define the maximum logging level, e.g. export BASE_LOG_LEVEL=”DEBUG”

BASE_LOG_COLOR Activate colored logging (current configuration best for dark background coloured terminals), e.g. export BASE_LOG_COLOR

BASE_LOG_FORMAT Select from a set of predefined logging formats: DEFAULT, MULTILINE, SHORT, example outputs are given below:

The DEFAULT format contains no linebreaks (here only due to fit the narrow presentation):

[20120120-11:58:00:577] [FATAL] - test_logger::A fatal error 
occurred (/tmp/test_logger/src/Main.cpp:10 - int main(int, char**))

The SHORT format reduces information to the log priority and the message:

[FATAL] - test_logger::A fatal error occurred

The MULTILINE format split each individual log message across a minimum of three lines:

[20120120-11:58:59:976] in int main(int, char**)
        /tmp/test_logger/src/Main.cpp:10
        [FATAL] - test_logger::A fatal error occurred