4 // Fraunhofer Institute for Open Communication Systems (FOKUS)
5 // Competence Center NETwork research (NET), St. Augustin, GERMANY
6 // Stefan Bund <g0dil@berlios.de>
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 2 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the
20 // Free Software Foundation, Inc.,
21 // 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24 \brief Config public header */
26 #ifndef HH_SENF_Utils_Logger_Config_
27 #define HH_SENF_Utils_Logger_Config_ 1
32 //#include "Config.mpp"
34 ///////////////////////////////hh.p////////////////////////////////////////
36 /** \defgroup config Configuration
38 The logger infrastructure provides for very fine-grained configuration of log messages. There
39 are two parts to this configuration: compile-time configuration and runtime configuration.
41 <em>Compile-time</em> configuration selects, which log statements will even be compiled. If
42 logging for a certain combination of stream, area and level is disabled at compile time, no code
43 will be generated for any such disabled log statement. This type of configuration is done using
46 <em>Runtime</em> configuration on the other hand deals with routing all those messages, which
47 are enabled at compile time to the logging targets. If a message is not routed, it will be
48 discarded. This allows to additionally disable messages at run-time. Message routing is managed
49 via the ::Target interface.
51 \section config_compile Compile time configuration
53 Compile time configuration is set on the compiler command line:
55 g++ ... -DSENF_LOG_CONF="(( (senf)(log)(Debug),(_),DISABLED ))
56 (( (senf)(log)(Debug),(foo)(SomeClass),VERBOSE ))
57 (( (_),(_),NOTICE ))" ...
59 The value is relatively complex; It's a Boost.Preprocessor style sequence of tuples, of which
60 the first and second elements are again sequences. What this boils down to, is that it allows to
61 configure compile time logging limits based on stream and optional area.
63 The above example disables all debug logging by setting the default log limit for all areas on
64 the \c senf::log::Debug stream to \c DISABLED. It enables debug logging only within the \c
65 foo::SomeClass area, where it is set to \c VERBOSE. Lastly, the global compile time limit is set
68 There are two standard uses for this configuration: Either to disable most logging in final
69 builds by changing the compile time limit to something like senf::log::IMPORTANT or to enable
70 senf::log::VERBOSE messages for some area:
72 # Disable debug logging below 'IMPORTANT' level
73 g++ ... -DSENF_LOG_CONF="(( (senf)(log)(Debug), (_), IMPORTANT ))"
75 # Or enable verbose messages for the 'some::Area' area
76 g++ ... -DSENF_LOG_CONF="(( (senf)(log)(Verbose), (some)(Area), VERBOSE ))"
79 All the entries specified via \c SENF_LOG_CONF are applied in a fixed order:
81 \li First the entries which have both a stream and an area specified are checked
82 \li next all entries with area but no stream given are checked
83 \li followed by all entries with a given stream but no area
84 \li and lastly if no match was found until now, a generic entry without stream and area is
86 \li if no matching entry is found, the default compile time limit of the stream is used
88 So an area specification has precedence over a stream specification.
90 \warning Enabling a message at compile time does \e not ensure, the message is shown. You
91 additionally need to \e route the message (see next chapter). This is especially true for \c
92 VERBOSE messages, which are default disabled at runtime.
94 \see \ref SENF_LOG_CONF
96 \section config_runtime Runtime configuration
98 The runtime configuration is performed by routing messages to one or more logging targets:
100 senf::log::ConsoleTarget & consoleLog (senf::log::ConsoleTarget::instance());
101 senf::log::FileTarget fileLog ("my.log");
103 consoleLog.route<senf::log::Debug>();
104 consoleLog.route<foo::Transactions, foo::SomeClass>(senf::log::Target::REJECT);
105 consoleLog.route<foo::Transactions, senf::log::IMPORTANT>();
107 fileLog.route<foo::Transactions>();
109 Here we see an already relatively complex setup: All debug messages (that is, those, which are
110 not disabled at compile time) are routed to the console. We also route important transactions to
111 the console \e except transactions from the \c foo::SomeClass area. The \c fileLog simply
112 receives all transaction log messages.
114 The routing statements are processed by the targets in order, the first matching rule will
115 decide a log messages fate for that target.
117 \warning You can \e only route those messages at runtime which have been compile-time
118 enabled. By default, \c VERBOSE messages are \e disabled at compile time. They must be
119 enabled \e explicitly by setting \c SENF_LOG_CONF so they can be routed.
121 \section config_fallback Fallback routing
123 There are two cases, where this setup may lead to inadvertently lost log messages:
124 \li When using a library which does internally use the Logger but not initializing the logger in
126 \li When log messages are created during initialization of static objects.
127 Since no route is set up in these cases, the messages will be dropped.
129 To counter this problem, the logger is initially in <em>fallback routing</em> state. If any log
130 message arrives in this state, the message will be logged to the console if it is above the
131 default runtime limit of it's stream. The first routing statement on any target will take the
132 logger out of this state and normal routing will take place.
134 \see \ref senf::log::Target
136 \section config_timesource Log message timing
138 One auxiliary aspect of logging is message timing. Each message is stamped with a time-stamp
139 giving the exact time the message was created. How the current date/time value is created may be
140 changed by setting a \e TimeSource. A TimeSource is an instance derived from
141 senf::log::TimeSource which will return the current universal time (UTC) when called.
143 By default, the logging library will call gettimeofday() for each log message. To change the
144 time source, just pass the new class or instance to senf::log::timeSource:
146 // Use senf::scheduler::eventTime() to time log messages
147 senf::log::timeSource<senf::scheduler::LogTimeSource>();
159 /** \brief Compile time configuration
161 This define symbol sets the compile time logger configuration. This symbol should normally
162 be set on the compiler command line.
164 The formal syntax of this option is:
168 <tr><td>conf</td> <td>::= \e element \e element* \n</td></tr>
169 <tr><td>element</td> <td>::= <tt>((</tt> \e optional_stream <tt>,</tt> \e optional_area <tt>,</tt> \e level <tt>))</tt> \n</td></tr>
170 <tr><td>optional_stream</td> <td>::= <tt>(_)</tt> | \e scope_seq \n</td></tr>
171 <tr><td>optional_area</td> <td>::= <tt>(_)</tt> | \e scope_seq \n</td></tr>
172 <tr><td>level</td> <td>::= \c VERBOSE | \c NOTICE | \c MESSAGE | \c IMPORTANT | \c CRITICAL | \c DISABLED \n</td></tr>
173 <tr><td>scope_seq</td> <td>::= \e scope \e scope* \n</td></tr>
174 <tr><td>scope</td> <td>::= <tt>(</tt> \e name <tt>)</tt> \n</td></tr>
175 <tr><td>name</td> <td>::= arbitrary C++ identifier</td></tr>
178 \ref SENF_LOG_CONF is a Boost.Preprocessor style sequence of 3-tuples.
180 The first tuple element \e optional_stream specifies the stream to match. If this is
181 <tt>(_)</tt>, the entry will match any stream.
183 The next tuple element, \e optional_area optionally restricts the entry to match only the
184 given area. If set to <tt>(_)</tt>, the area is left unrestricted.
186 The last tuple element \e level defines the compile time log level. Messages with a level
187 below this are discarded at compile time.
189 Both \e optional_stream and \e optional_area are given as a \e scope_seq. A scope sequence
190 is a fully qualified C++ identifier placed into a sequence: <tt>foo::bar::baz</tt> is
191 represented by <tt>(foo)(bar)(baz)</tt>.
193 # define SENF_LOG_CONF
197 /** \brief Check, if logging is enabled for stream/area/level tuple
199 This is a template meta-function which will check, whether logging to the given combination
200 of parameters \a Stream, \a Area and \a Level is compile-time enabled. The logging might
201 still be disabled at runtime.
203 if (senf::log::Enabled<senf::log::Debug,
204 senf::log::DefaultArea,
205 senf::log::VERBOSE>::value) {
210 Since the \e value member is a compile time constant, the compiler will completely optimize
211 away this block of code when logging is disabled.
213 template <class Stream, class Area, class Level>
216 static const bool value = (
217 (Level::value == NONE::value ? Stream::defaultLevel::value : Level::value)
218 >= detail::Config<Stream,Area>::compileLimit::value );
225 ///////////////////////////////hh.e////////////////////////////////////////
226 //#include "Config.cci"
227 //#include "Config.ct"
228 //#include "Config.cti"
235 // comment-column: 40
236 // c-file-style: "senf"
237 // indent-tabs-mode: nil
238 // ispell-local-dictionary: "american"
239 // compile-command: "scons -u test"