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+// Copyright (C) 2013-2014 Internet Systems Consortium, Inc. ("ISC")
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+//
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+// Permission to use, copy, modify, and/or distribute this software for any
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+// purpose with or without fee is hereby granted, provided that the above
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+// copyright notice and this permission notice appear in all copies.
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+//
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+// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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+// AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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+// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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+// PERFORMANCE OF THIS SOFTWARE.
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+
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+// Note: the prefix "log" to all labels is an abbreviation for "Logging"
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+// and is used to prevent a clash with symbols in any other Doxygen file.
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+
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+/**
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+@page logBind10Logging BIND 10 Logging
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+
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+@section logBasicIdeas Basic Ideas
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+
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+The BIND 10 logging system is based on the log4J logging system
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+common in Java development, and includes the following ideas:
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+
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+- A set of severity levels.
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+- A hierarchy of logging sources.
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+- Separation of message use from message text.
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+
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+@subsection logSeverity Message Severity
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+Each message logged by BIND 10 has a severity associated with it, ranging
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+from FATAL - the most severe - to DEBUG - messages output as the code
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+executes to facilitate debugging. In order of decreasing severity,
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+the levels are:
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+
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+<dl>
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+<dt>FATAL</dt>
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+<dd>The program has encountered an error that is so severe that it
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+cannot continue (or there is no point in continuing). For example, an
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+unhandled exception generated deep within the code has been caught by the
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+top-level program. When a fatal error has been logged, the program will
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+exit immediately (or shortly afterwards) after dumping some diagnostic
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+information.</dd>
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+
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+<dt>ERROR</dt>
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+<dd>Something has happened such that the program can continue but the
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+results for the current (or future) operations cannot be guaranteed to
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+be correct, or the results will be correct but the service is impaired.
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+For example, the program started but attempts to open one or more network
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+interfaces failed.</dd>
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+
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+<dt>WARN</dt>
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+<dd>(Warning) An unusual event happened. Although the program will
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+continue working normally, the event was sufficiently out of the ordinary
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+to warrant drawing attention to it. For example, the authoritative
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+server loaded a zone that contained no resource records.</dd>
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+
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+<dt>INFO</dt>
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+<dd>(Information) A normal but significant event has occurred that should
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+be recorded, e.g. the program has started or is just about to terminate,
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+a new zone has been created, etc.</dd>
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+
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+<dt>DEBUG</dt>
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+<dd>Debug messages are output at this severity. Each message also
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+has a debug level associated with it, ranging from 0 (the default)
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+for high-level messages and level 99 (the maximum) for the the lowest
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+level.</dd>
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+</dl>
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+
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+When logging is enabled for a component, it is enabled for a particular
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+severity level and all higher severities. So if logging is enabled
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+for INFO messages, WARN, ERROR and FATAL messages will also be logged,
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+but not DEBUG ones. If enabled for ERROR, only ERROR and FATAL messages
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+will be logged.
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+
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+As noted above, DEBUG messages are also associated with a debug level.
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+This allows the developer to control the amount of debugging information
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+produced; the higher the debug level, the more information is output.
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+For example, if debugging the NSAS (nameserver address store), debug
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+levels might be assigned as follows: a level 0 debug message records
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+the creation of a new zone, a level 10 logs every timeout when trying
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+to get a nameserver address, a level of 50 records every query for an
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+address and a level of 70 records every update of the round-trip time.
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+
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+Like severities, levels are cumulative; so if level 25 is set as the
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+debug level, all debug messages associated levels 0 to 25 (inclusive)
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+will be output. In fact, it is probably easier to visualise the debug
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+levels as part of the severity system:
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+@code
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+FATAL Most severe
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+ERROR
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+WARN
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+INFO
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+DEBUG level 0
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+DEBUG level 1
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+ :
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+DEBUG level 99 Least severe
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+@endcode
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+When a particular debug level is set, it - and all debug levels and
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+severities above it - will be logged.
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+
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+To try to ensure that the information from different modules is roughly
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+comparable for the same debug level, a set of standard debug levels has
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+been defined for common types of debug output. (These can be found in
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+@ref log_dbglevels.h) However, modules are free to set their own debug
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+levels or define additional ones.
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+
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+@subsection logHierarchical Hierarchical Logging System
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+
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+When a program writes a message to the logging system, it does so using an
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+instance of the @ref isc::log::Logger class. As well as performing the
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+write of the message, the logger identifies the source of the message:
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+different sources can write to different destinations and can log
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+different severities of messages. For example, the logger associated
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+with the resolver's cache code could write debugging and other messages
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+to a file while all other components only write messages relating to
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+errors to the syslog file.
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+
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+The loggers are hierarchical in that each logger is the child of another
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+logger. The top of the hierarchy is the root logger; this does not
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+have a parent. The reason for this hierarchy is that unless a logger
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+explicitly assigns a value to an attribute (such as severity of messages
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+it should log), it picks it up the value from the parent. In BIND 10,
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+each component (b10-auth, b10-resolver etc.) has a root logger (named
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+after the program) and every other logger in the component is a child
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+of that. So in the example above, the error/syslog attributes could be
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+associated with the b10-resolver logger while the logger associated with
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+the cache sets its own values for the debug/file attributes.
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+
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+More information about the logging hierarchy can be found in the section
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+on Logging configuration in the <a
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+href="http://bind10.isc.org/docs/bind10-guide.html#logging">BIND 10
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+Guide</a>.
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+
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+@subsection logSeparationUseText Separation of Messages Use from Message Text
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+
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+Separating the use of the message from the text associated with it -
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+in essence, defining message text in an external file - allows for the
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+replacement the supplied text of the messages with a local language version.
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+It also means that other attributes can be associated with the message,
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+for example, an explanation of the meaning of the message and other
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+information such as remedial action in the case of errors.
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+
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+Each message has an identifier such as "LOG_WRITE_ERROR".
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+Within the program, this is the symbol passed to the logging system
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+which uses the symbol as an index into a dictionary to retrieve the message
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+associated with it (e.g. "unable to open %1 for input"), after which it
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+substitutes any message parameters (in this example, the name of the file
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+where the write operation failed) and logs the result to the destination.
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+
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+In BIND 10, a the default text for each message is linked into the
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+program. Each program is able to read a locally-defined message file
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+when it starts, updating the stored definitions with site-specific text.
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+When the message is logged, the updated text is output. However, the
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+message identifier is always included in the output so that the origin
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+of the message can be identified even if the text has been changed.
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+
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+@note Local message files have not yet been implemented in BIND 10.
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+
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+
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+
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+@section logDeveloperUse Using Logging in a BIND 10 Component
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+
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+The steps in using the logging system in a BIND 10 component (such as
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+an executable or library) are:
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+
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+<ol>
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+<li>Create a message file. This defines messages by an identification
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+string and and text that explains the message in more detail. Ideally the
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+file should have a file type of ".mes".</li>
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+
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+<li>Run it through the message compiler to produce the files for your
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+module. This step should be included in the build process. The message
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+compiler is a BIND10 program and is one of the first programs built and
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+linked in the build process. As a result, it should be available for
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+compiling the message files of all BIND 10 components and libraries.
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+
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+For C++ development, the message compiler produces two files in the
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+default directory, having the same name as the input file but with file
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+types of ".h" and ".cc". For Python, the message compiler will produce
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+a Python module containing the symbols.</li>
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+
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+<li>Include the resultant files in your source code to define message symbols,
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+and (for C++) compile the code and link it into your program.</li>
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+
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+<li>Declare loggers in your code and use them to log messages.</li>
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+
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+<li>Call the logger initialization function in the program's main module.</li>
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+
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+</ol>
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+
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+The following sections describe these steps in more detail.
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+
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+
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+@subsection logMessageFiles Create a Message File
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+
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+A message file contains message definitions. Typically there
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+will be one message file for each component that uses BIND 10 logging.
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+An example file could be:
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+
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+@code
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+# Example message file
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+
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+$NAMESPACE isc::log
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+
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+% LOG_UNRECOGNISED_DIRECTIVE line %1: unrecognised directive '%2'
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+A line starting with a dollar symbol was found, but the first word on the line
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+(shown in the message) was not a recognised message compiler directive.
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+
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+% LOG_WRITE_ERROR error writing to %1: %2
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+The specified error was encountered by the message compiler when writing to
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+the named output file.
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+@endcode
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+
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+Points to note are:
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+
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+<ul>
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+<li>Leading and trailing spaces are trimmed from each line before it
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+is processed. Although the above example has every line starting at
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+column 1, the lines could be indented if desired.</li>
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+
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+<li>Lines starting with "#" are comments are are ignored. Comments must
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+be on a line by themselves; inline comments will be interpreted as part
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+of the text of that line.</li>
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+
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+<li>Lines starting with "$" are directives. At present, just one
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+directive is recognised:
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+ <dl>
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+ <dt>$NAMESPACE <namespace-name></dt>
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+ <dd>The sole argument is the name of the namespace in which the
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+ symbols are created. In the absence of a $NAMESPACE directive,
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+ symbols will be put in the anonymous namespace.</dd>
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+ </dl>
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+</li>
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+
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+<li>Lines starting with "%" are message definitions and comprise the message
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+identification and the message text. For example:
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+@code
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+% LOG_WRITE_ERROR error writing to %1: %2
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+@endcode
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+
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+There may be zero or more spaces between the leading "%" and the
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+message identification (which, in the example above, is the string
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+"LOG_WRITE_ERROR").</li>
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+
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+<li>The message identification can be any string of letters, digits and
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+underscores, but must not start with a digit.</li>
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+
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+<li>The rest of the line - from the first non-space character to the
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+last non- space character - is the text of the message. There are no
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+restrictions on what characters may be in this text, other than they be
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+printable (so both single-quote (') and double-quote (") characters are
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+allowed). The message text may include replacement tokens (the strings
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+"%1", "%2" etc.). When a message is logged, these are replaced with the
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+arguments passed to the logging call: %1 refers to the first argument,
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+%2 to the second etc. Within the message text, the placeholders can
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+appear in any order and placeholders can be repeated. Otherwise, the
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+message is printed unmodified.</li>
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+
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+<li>Remaining lines indicate an explanation for the preceding message.
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+The explanation can comprise multiple paragraphs, the paragraphs being
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+separated by blank lines. These lines are intended to be processed by a
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+separate program to generate an error messages manual; they are ignored
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+by the message compiler.</li>
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+
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+<li>Except when used to separate paragraphs in the message explanation,
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+blank lines are ignored.</li>
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+</ul>
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+
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+Although there are few restriction on what can be in the message
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+identifcation and text, there are a number of conventions used by BIND
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+10, both in the contents of the message and in the usage. All code
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+should adhere to these:
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+
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+<ul>
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+<li>Message identifications should include at least one underscore.
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+The component before the first underscore is a string indicating the
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+origin of the message, and the remainder describes the condition.
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+So in the example above, the LOG indicates that the error originated
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+from the logging library and the "WRITE_ERROR" indicates that there was
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+a problem in a write operation.</li>
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+
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+<li>The part of the message identification describing the error (e.g.
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+"WRITE_ERROR" in the example above) should comprise no more than
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+two or three words separated by underscores. An excessive number
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+of words or overly long message identification should be avoided;
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+such information should be put in the text of the message. For example,
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+"RESOLVER_ERROR_FETCHING_NAME_FROM_UPSTREAM_SERVER" is excessively long,
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+"RESOLVER_FETCH_ERROR" being better.</li>
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+
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+<li>Similarly, the text of the message should be reasonably concise. It should
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+include enough information (possibly supplied at run-time in the form of
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+parameters) to allow further investigations to be undertaken if required.
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+
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+Taking the above example, a suitable error message to indicate that the
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+resolver has failed to read a name from an upstream authoritative server
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+could be:
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+
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+@code
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+% RESOLVER_FETCH_ERROR fetch from %1 failed, error code %2 (%3)
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+@endcode
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+
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+... where %1 indicates the name or IP address of the server to which the
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+fetch was sent, %2 the errno value returned and %3 the message associated
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+with that error number (retrieved via a call to "strerror()").
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+
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+</li>
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+
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+<li>The message should not have a comma after the message identification.
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+The message text should neither start with a capital letter (unless
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+the first word is a proper noun or is normally written in capitals)
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+nor end with a period. The message reporting system takes care of such
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+punctuation.</li>
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+
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+<li>The parameters substituted into the message text should not include
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+line breaks. Messages are normally output to the syslog file which
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+has the inbuilt assumption of one line per message. Splitting a message
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+across multiple lines makes it awkward to search the file for messages
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+and associated information.</li>
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+
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+<li>The message identifier should be unique across the entire BIND 10
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+system. (An error will be reported at system start-up if an identifier
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+is repeated.)</li>
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+
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+<li>A particular message identifier should only be used at one place in
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+the BIND 10 code. In this way, if the message indicates a problem, the
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+code in question can be quickly identified.</li>
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+
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+<li>The explanation of the message - the free-form text following the
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+message identification - appears in the BIND 10 message manual. It
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+should:
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+
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+<ul>
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+<li>Describe the serverity of the message (debug, informational etc.)</li>
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+
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+<li>Expand on the text of the message. In some cases, such as
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+debug messages, the message text may provide more or less sufficient
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+description. For warnings and errors, the explanation should provide
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+sufficient background to the problem to allow a non-developer to
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+understand the issue and to begin fault-finding. If possible, the
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+explanation should also include suggested remedial action.</li>
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+</ul>
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+</ul>
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+
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+@subsection logSourceFiles Produce Source Files
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+The message file created in the previous step is then run through the
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+message compiler to produce source files that are included in the BIND
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+10 programs.
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+
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+@subsubsection logMessageCompiler Message Compiler
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+The message compiler is a program built in the src/log/compiler directory.
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+It is invoked by the command:
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+@code
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+message [-h] [-v] [-p] [-d dir] <message-file>
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+@endcode
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+"-v" prints the version number and exits; "-h" prints brief help text.
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+The compiler produces source files for C++ unless the "-p" switch is
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+specified, in which case it produces Python code. Finally, the "-d"
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+switch directs the compiler to produce the output files in the specified
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+directory (the default being the current working directory).
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+
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+<b>C++ Files</b><br/>
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+Without the "-p" option, the message compiler processes the message file
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+to produce two files:
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+
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+<ol>
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+<li>A C++ header file (called <message-file-name>.h) holding lines of
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+the form:
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+@code
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+namespace <namespace-name> {
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+ extern const isc::log::MessageID LOG_BAD_DESTINATION;
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+ extern const isc::log::MessageID LOG_BAD_SEVERITY;
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+ :
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+}
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+@endcode
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+The symbols define keys in the global message dictionary, with
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+the namespace enclosing the symbols set by the $NAMESPACE directive.
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+(This is the reason for the restriction on message identifiers - they
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+have to be valid C++ symbol names.)</li>
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+
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|
+<li>A C++ source file (called <message-file-name>.cc) that holds the definitions
|
|
|
+of the global symbols and code to insert the symbols and messages into
|
|
|
+an internal dictionary.
|
|
|
+
|
|
|
+Symbols are defined to be equal to strings equal to the identifier, e.g.
|
|
|
+@code
|
|
|
+extern const isc::log::MessageID LOG_BAD_DESTINATION = "LOG_BAD_DESTINATION";
|
|
|
+extern const isc::log::MessageID LOG_BAD_SEVERITY = "LOG_BAD_SEVERITY";
|
|
|
+ :
|
|
|
+@endcode
|
|
|
+(The current implementation allows symbols to be compared. However,
|
|
|
+use of strings should not be assumed - a future implementation may change
|
|
|
+this.) In addition, the file declares an array of identifiers/messages
|
|
|
+and an object to add them to the global dictionary, e.g.:
|
|
|
+@code
|
|
|
+namespace {
|
|
|
+ const char* values[] = {
|
|
|
+ "LOG_BAD_DESTINATION", "unrecognized log destination: %1",
|
|
|
+ "LOG_BAD_SEVERITY", "unrecognized log severity: %1",
|
|
|
+ :
|
|
|
+ NULL
|
|
|
+ };
|
|
|
+ const isc::log::MessageInitializer initializer(values);
|
|
|
+}
|
|
|
+@endcode
|
|
|
+
|
|
|
+The constructor of the @ref isc::log::MessageInitializer object retrieves
|
|
|
+the singleton global @ref isc::log::MessageDictionary object (created
|
|
|
+using standard methods to avoid the "static initialization fiasco") and
|
|
|
+adds each identifier and associated text to it. These constructors are run
|
|
|
+when the program starts; a check is made as each identifier is added and,
|
|
|
+if the identifier already exists in the dictionary, a warning message
|
|
|
+is printed to the main logging output when logging is finally enabled.
|
|
|
+The appearance of such a message indicates a programming error.
|
|
|
+</li>
|
|
|
+</ol>
|
|
|
+
|
|
|
+<b>Python Files</b><br/>
|
|
|
+If the "-p" option is given, the compiler produces a Python module defining
|
|
|
+the messages. The content of this is of the form:
|
|
|
+@code
|
|
|
+import isc.log
|
|
|
+ :
|
|
|
+LOG_WRITE_ERROR = isc.log.create_message("LOG_WRITE_ERROR",
|
|
|
+ "error writing to %1 : %2")
|
|
|
+@endcode
|
|
|
+(The definition is output on one line - it is split across two lines in this
|
|
|
+document for readability.)
|
|
|
+
|
|
|
+The module can be imported into other Python code, and messages logged
|
|
|
+in a similar way to C++ using the Python logging library.
|
|
|
+
|
|
|
+@subsubsection logMakefile Include Message Compilation in Makefile
|
|
|
+The source file for the messages is the ".mes" file, but the files used
|
|
|
+by the code (which, in the case of C++, must be compiled and linked)
|
|
|
+are the output of the message compiler. (The compiler is produced very
|
|
|
+early on in the BIND 10 build sequence, so is available for use in the
|
|
|
+building of subsequent components.) To allow this, certain dependencies
|
|
|
+must be included in the Makefile.am for each component that uses logging.
|
|
|
+
|
|
|
+<b>Including Message files in C++ Component Builds</b><br/>
|
|
|
+The following segment from the "hooks" Makefile.am illustrates
|
|
|
+the entries needed.
|
|
|
+@code
|
|
|
+# Define rule to build logging source files from message file
|
|
|
+hooks_messages.h hooks_messages.cc: s-messages
|
|
|
+
|
|
|
+s-messages: hooks_messages.mes
|
|
|
+ $(top_builddir)/src/lib/log/compiler/message $(top_srcdir)/src/lib/hooks/hooks_messages.mes
|
|
|
+ touch $@
|
|
|
+
|
|
|
+# Tell automake that the message files are built as part of the build process
|
|
|
+# (so that they are built before the main library is built).
|
|
|
+BUILT_SOURCES = hooks_messages.h hooks_messages.cc
|
|
|
+
|
|
|
+# Ensure that the message file is included in the distribution
|
|
|
+EXTRA_DIST = hooks_messages.mes
|
|
|
+
|
|
|
+# Get rid of generated message files on a clean
|
|
|
+CLEANFILES = *.gcno *.gcda hooks_messages.h hooks_messages.cc s-messages
|
|
|
+@endcode
|
|
|
+The first two rules relate the output .h and .cc files produced by the
|
|
|
+message compiler to the input .mes file. The intermediate "s-messages"
|
|
|
+file is used to overcome synchronization issues with parallel builds
|
|
|
+(where "make" uses multiple processes running in parallel). Note that the
|
|
|
+reference to both the compiler and the input message file are via absolute
|
|
|
+paths defined in terms of Automake macros. In particular it is important
|
|
|
+that the message compiler - which is created during the build process - is
|
|
|
+referred to via the "top_builddir" macro, whereas the input message file -
|
|
|
+which is in the repository - is accessed through the "top_srcdir" macro.
|
|
|
+
|
|
|
+The BUILT_SOURCES line notifies the Automake that the .h and .cc files
|
|
|
+need to be created before they can be used in the compilation, so
|
|
|
+instructs it to organse things so that the message compiler is run first.
|
|
|
+
|
|
|
+As the .mes file is not directly included in any compilation, it will
|
|
|
+not be automatically copied into a distribution created through this
|
|
|
+Makefile.am. The EXTRA_DIST line informs Automake that this file does
|
|
|
+need to be included.
|
|
|
+
|
|
|
+Finally, the intermediate files - the .cc and .h file, as well as the
|
|
|
+intermediate s-messages file - need to be removed when "make clean" is run.
|
|
|
+These files are therefore included in the definition of the CLEANFILES macro.
|
|
|
+
|
|
|
+Not shown are the Makefile.am lines where the .h and .cc file are used. These
|
|
|
+are the same as other lines specifying .h and .cc source files.
|
|
|
+
|
|
|
+<b>Including Message files in Python Component Builds</b><br/>
|
|
|
+The following (modified) segments from the "xfrin" Makefile.am illustrates
|
|
|
+the entries needed.
|
|
|
+
|
|
|
+@code
|
|
|
+CLEANFILES = $(PYTHON_LOGMSGPKG_DIR)/work/xfrin_messages.py
|
|
|
+CLEANFILES += $(PYTHON_LOGMSGPKG_DIR)/work/xfrin_messages.pyc
|
|
|
+ :
|
|
|
+EXTRA_DIST += xfrin_messages.mes
|
|
|
+ :
|
|
|
+# Define rule to build logging source files from message file
|
|
|
+$(PYTHON_LOGMSGPKG_DIR)/work/xfrin_messages.py : xfrin_messages.mes
|
|
|
+ $(top_builddir)/src/lib/log/compiler/message \
|
|
|
+ -d $(PYTHON_LOGMSGPKG_DIR)/work -p $(srcdir)/xfrin_messages.mes
|
|
|
+@endcode
|
|
|
+The CLEANFILES lines remove the created Python (and compiled Python)
|
|
|
+code when "make clean" is run.
|
|
|
+
|
|
|
+The EXTRA_DIST line ensures that the .mes file is copied to the
|
|
|
+distribution tarball.
|
|
|
+
|
|
|
+The final dependency shows the use of the message compiler to
|
|
|
+create the Python message module in a working directory.
|
|
|
+
|
|
|
+
|
|
|
+@subsection logUsage Using Logging Files in Program Development
|
|
|
+
|
|
|
+@subsubsection logCppUsage Use in a C++ Program or Module
|
|
|
+To use logging in a C++ program or module:
|
|
|
+
|
|
|
+<ol>
|
|
|
+<li>Build the message header file and source file as described above.</li>
|
|
|
+
|
|
|
+<li>In each C++ file in which logging is to be used, declare a logger
|
|
|
+through which the message will be logged.
|
|
|
+
|
|
|
+@code
|
|
|
+isc::log::Logger logger("name");
|
|
|
+@endcode
|
|
|
+This declaration can be per-function, or it can be declared statically
|
|
|
+in file scope. The string passed to the constructor is the name of
|
|
|
+the logger (it can be any string) and is used when configuring it.
|
|
|
+(Remember though that the name of root logger for the program will be
|
|
|
+prepended to the name chosen. So if, for example, the name "cache"
|
|
|
+is chosen and the model is included in the "b10-resolver" program, the
|
|
|
+full name of the logger will be "b10-resolver.cache".) Loggers with
|
|
|
+the same name share the same configuration. For this reason if, as is
|
|
|
+usual, messages logged in different files in the same component (e.g.
|
|
|
+hooks module, nameserver address store, etc.) originate from loggers
|
|
|
+with the same name, the logger declaration can be placed into a header
|
|
|
+file.</li>
|
|
|
+
|
|
|
+<li>Issue logging calls using supplied macros in "log/macros.h", e.g.
|
|
|
+@code
|
|
|
+LOG_ERROR(logger, LOG_WRITE_ERROR).arg("output.txt");
|
|
|
+LOG_DEBUG(nsas_logger, NSAS_DBG_TRACE, NSAS_LOOKUP_CANCEL).arg(zone);
|
|
|
+@endcode
|
|
|
+All macros (with the exception of LOG_DEBUG) take two arguments:
|
|
|
+the C++ logger object that will be used to log the message, and the
|
|
|
+identification of the message to be logged. LOG_DEBUG takes three
|
|
|
+arguments, the additional one being the debug level associated with
|
|
|
+the message. The .arg() call appended to the end of the LOG_XXX()
|
|
|
+macro handles the arguments to the message. A chain of these is used
|
|
|
+in cases where a message takes multiple arguments, e.g.
|
|
|
+@code
|
|
|
+LOG_DEBUG(nsas_logger, NSAS_DBG_RTT, NSAS_UPDATE_RTT)
|
|
|
+ .arg(addresses_[family][index].getAddress().toText())
|
|
|
+ .arg(old_rtt).arg(new_rtt);
|
|
|
+@endcode
|
|
|
+Using the macros is more efficient than direct calls to the methods on
|
|
|
+the logger class: they avoid the overhead of evaluating the parameters
|
|
|
+to arg() if the logging settings are such that the message is not going
|
|
|
+to be output (e.g. it is a DEBUG message and the logging is set to output
|
|
|
+messages of INFO severity or above).</li>
|
|
|
+
|
|
|
+<li>The main program unit must include a call to isc::log::initLogger()
|
|
|
+(described in more detail below) to set the initial logging severity, debug log
|
|
|
+level, and external message file.
|
|
|
+</ol>
|
|
|
+
|
|
|
+@subsubsection logPythonUsage Use in a Python Module
|
|
|
+To use logging in a Python module:
|
|
|
+<ol>
|
|
|
+<li>Build message module as described above.</li>
|
|
|
+
|
|
|
+<li>Declare a logger through which the message will be logged.
|
|
|
+@code
|
|
|
+isc.log.Logger logger("name")
|
|
|
+@endcode
|
|
|
+The string passed to the constructor is the name of the logger (it can
|
|
|
+be any string) and is used when configuring it. Loggers with the same
|
|
|
+name share the same configuration.</li>
|
|
|
+
|
|
|
+<li>Issue calls to the logging methods:
|
|
|
+@code
|
|
|
+logger.error(LOG_WRITE_ERROR, "output.txt")
|
|
|
+@endcode
|
|
|
+The message parameters are included as trailing arguments in the
|
|
|
+logger call.</li>
|
|
|
+
|
|
|
+<li>The main program unit must include a call to isc.log.init() (described
|
|
|
+in more detail below) to set the to set the logging severity, debug log
|
|
|
+level, and external message file. The settings remain in effect until
|
|
|
+the logging configuration is read, so are the ones used during program
|
|
|
+initialization.</li>
|
|
|
+</ol>
|
|
|
+
|
|
|
+
|
|
|
+@subsection logInitialization Logging Initialization
|
|
|
+In all cases, if an attempt is made to use a logging method before
|
|
|
+the logging has been initialized, the program will terminate with a
|
|
|
+LoggingNotInitialized exception.
|
|
|
+
|
|
|
+@subsection logInitializationCpp C++ Initialization
|
|
|
+Logging Initialization is carried out by calling @ref
|
|
|
+isc::log::initLogger(). There are two variants to the call, one for
|
|
|
+use by production programs and one for use by unit tests.
|
|
|
+
|
|
|
+@subsubsection logInitializationCppVariant1 Variant #1, Used by Production Programs
|
|
|
+The call that should be used by all production programs is:
|
|
|
+@code
|
|
|
+void isc::log::initLogger(const std::string& root,
|
|
|
+ isc::log::Severity severity = isc::log::INFO,
|
|
|
+ int dbglevel = 0, const char* file = NULL,
|
|
|
+ bool buffer = false);
|
|
|
+@endcode
|
|
|
+Arguments are:
|
|
|
+<dl>
|
|
|
+<dt><code>root</code></dt>
|
|
|
+<dd>Name of the root logger. This should be the name of the program
|
|
|
+(e.g. "b10-auth") and is used when configuring logging.</dd>
|
|
|
+
|
|
|
+<dt><code>severity</code></dt>
|
|
|
+<dd>Default severity that the program will start logging with. Although
|
|
|
+this may be overridden when the program obtains its configuration from
|
|
|
+the configuration database, this is the severity that it used until then.
|
|
|
+The logging severity is one of the enum defined in @ref logger.h, i.e.
|
|
|
+
|
|
|
+@code
|
|
|
+isc::log::DEBUG
|
|
|
+isc::log::INFO
|
|
|
+isc::log::WARN
|
|
|
+isc::log::ERROR
|
|
|
+isc::log::FATAL
|
|
|
+isc::log::NONE
|
|
|
+@endcode
|
|
|
+
|
|
|
+(The level NONE may be used to disable logging.)
|
|
|
+</dd>
|
|
|
+
|
|
|
+<dt><code>dbglevel</code></dt>
|
|
|
+<dd>The debug log level is only interpreted when the severity is
|
|
|
+isc::log::DEBUG and is an integer ranging from 0 to 99. 0 should be
|
|
|
+used for the highest-level debug messages and 99 for the lowest-level
|
|
|
+(and typically more verbose) messages.</dd>
|
|
|
+
|
|
|
+<dt><code>file</code></dt>
|
|
|
+<dd>The name of a local message file. This will be read and its
|
|
|
+definitions used to replace the compiled-in text of the messages.
|
|
|
+The default value of NULL indicates that no local message file is
|
|
|
+supplied.</dd>
|
|
|
+
|
|
|
+<dt><code>buffer</code></dt>
|
|
|
+<dd>If set to true, initial log messages will be internally buffered,
|
|
|
+until the first time a logger specification is processed. This
|
|
|
+way the program can use logging before even processing its logging
|
|
|
+configuration. As soon as any specification is processed (even an
|
|
|
+empty one), the buffered log messages will be flushed according to
|
|
|
+the specification. Note that if this option is used, the program
|
|
|
+SHOULD call one of the @ref isc::log::LoggerManager::process() calls.
|
|
|
+(If you are using the built-in logging configuration handling in @ref
|
|
|
+isc::config::ModuleCCSession, this is automatically handled.) If the
|
|
|
+program exits before this is done, all log messages are dumped in a raw
|
|
|
+format to stdout (so that no messages get lost).</dd>
|
|
|
+</dl>
|
|
|
+
|
|
|
+@subsubsection logInitializationCppVariant2 Variant #2, Used by Unit Tests
|
|
|
+@code
|
|
|
+void isc::log::initLogger()
|
|
|
+@endcode
|
|
|
+This is the call that should be used by unit tests. In this variant,
|
|
|
+all the options are supplied by environment variables: it should not
|
|
|
+be used for production programs to avoid the chance that the program
|
|
|
+operation is affected by inadvertently-defined environment variables. The
|
|
|
+environment variables are:
|
|
|
+
|
|
|
+<dl>
|
|
|
+<dt>B10_LOGGER_ROOT</dt>
|
|
|
+<dd>Sets the "root" for the unit test. If not defined, the name "bind10"
|
|
|
+is used.</dd>
|
|
|
+
|
|
|
+<dt>B10_LOGGER_SEVERITY</dt>
|
|
|
+<dd>The severity to set for the root logger in the unit test.
|
|
|
+Valid values are "DEBUG", "INFO", "WARN", "ERROR", "FATAL" and "NONE".
|
|
|
+If not defined, "INFO" is used.</dd>
|
|
|
+
|
|
|
+<dt>B10_LOGGER_DBGLEVEL</dt>
|
|
|
+<dd>If B10_LOGGER_SEVERITY is set to "DEBUG", the debug level. This can
|
|
|
+be a number between 0 and 99, and defaults to 0.</dd>
|
|
|
+
|
|
|
+<dt>B10_LOGGER_LOCALMSG</dt>
|
|
|
+<dd>If defined, points to a local message file. The default is not to
|
|
|
+use a local message file.</dd>
|
|
|
+
|
|
|
+<dt>B10_LOGGER_DESTINATION</dt>
|
|
|
+<dd>The location to which log message are written. This can be one of:
|
|
|
+<ul>
|
|
|
+<li><b>stdout</b> Message are written to stdout.</li>
|
|
|
+<li><b>stderr</b> Messages are written to stderr.</li>
|
|
|
+<li><b>syslog[:facility]</b> Messages are written to syslog. If the
|
|
|
+optional "facility" is used, the messages are written using that facility.
|
|
|
+(This defaults to "local0" if not specified.)</li>
|
|
|
+<li><b>Anything else</b> Interpreted as the name of a file to which
|
|
|
+output is appended. If the file does not exist, a new one is opened.</li>
|
|
|
+</ul>
|
|
|
+In the case of "stdout", "stderr" and "syslog", they must be written exactly
|
|
|
+as is - no leading or trailing spaces, and in lower-case.</dd>
|
|
|
+</dl>
|
|
|
+
|
|
|
+@subsection logInitializationPython Python Initialization
|
|
|
+To initialize the logger in a Python program, the "init" method must be
|
|
|
+called:
|
|
|
+@code
|
|
|
+isc.log.init(name, severity, debuglevel, file, buffer)
|
|
|
+@endcode
|
|
|
+
|
|
|
+<dl>
|
|
|
+<dt><code>name</code></dt>
|
|
|
+<dd>String giving the name of the root logger. This is the only mandatory
|
|
|
+argument, the rest are optional.</dd>
|
|
|
+
|
|
|
+<dt><code>severity</code></dt>
|
|
|
+<dd>The severity, and is one of the strings "DEBUG", INFO" etc.
|
|
|
+The default is "INFO".</dd>
|
|
|
+
|
|
|
+<dt><code>debuglevel</code></dt>
|
|
|
+<dd>Debug level, an integer between 0 and 99. A default value of 0 will
|
|
|
+be used if this is not specified.</dd>
|
|
|
+
|
|
|
+<dt><code>file</code></dt>
|
|
|
+<dd>Name of the external message file (if present). By default, no
|
|
|
+external message file is used.</dd>
|
|
|
+
|
|
|
+<dt><code>buffer</code></dt>
|
|
|
+<dd>If set to true, initial log messages will be internally buffered,
|
|
|
+until the first time a logger specification is processed. This
|
|
|
+way the program can use logging before even processing its logging
|
|
|
+configuration. By default, no buffer is used.</dd>
|
|
|
+</dl>
|
|
|
+
|
|
|
+
|
|
|
+@section logNotes Notes on the Use of Logging
|
|
|
+One thing that should always be kept in mind is whether the logging
|
|
|
+could be used as a means for a DOS attack. For example, if a warning
|
|
|
+message is logged every time an invalid packet is received, an attacker
|
|
|
+could simply send large numbers of invalid packets. Of course, warnings
|
|
|
+could be disabled (or just warnings for that that particular logger),
|
|
|
+but nevertheless the message is an attack vector. As a general rule,
|
|
|
+if the message can be triggered by a user action, it can be used as an
|
|
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+attack vector.
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+
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+There are two approaches to get round this:
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+<ol>
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+<li>Log messages generated by such user actions as DEBUG messages. DEBUG
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+is not enabled by default, so these events will not be recorded unless
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+DEBUG is specifically enabled. Choosing a suitable debug level for
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+such messages will select only those messages and not the more general
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+debug messages.</li>
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+
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+<li>Record system-related and packet-related messages via different
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+loggers. As the loggers are independent and the severity levels
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+independent, fine-tuning of what and what is not recorded can be achieved.</li>
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+
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+</ol>
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+*/
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Stephen Morris