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// Copyright (C) 2011-2022 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
#ifndef LOGGER_H
#define LOGGER_H
#include <atomic>
#include <cstdlib>
#include <cstring>
#include <mutex>
#include <string>
#include <exceptions/exceptions.h>
#include <log/logger_level.h>
#include <log/message_types.h>
#include <log/log_formatter.h>
#include <log/output_option.h>
namespace isc {
namespace log {
namespace interprocess {
// Forward declaration to hide implementation details from normal
// applications.
class InterprocessSync;
}
/// \page LoggingApi Logging API
/// \section LoggingApiOverview Overview
/// Kea logging uses the concepts of the widely-used Java logging
/// package log4j (https://logging.apache.org/log4j/), albeit implemented
/// in C++ using an open-source port. Features of the system are:
///
/// - Within the code objects - known as loggers - can be created and
/// used to log messages. These loggers have names; those with the
/// same name share characteristics (such as output destination).
/// - Loggers have a hierarchical relationship, with each logger being
/// the child of another logger, except for the top of the hierarchy, the
/// root logger. If a logger does not log a message, it is passed to the
/// parent logger.
/// - Messages can be logged at severity levels of FATAL, ERROR, WARN, INFO
/// or DEBUG. The DEBUG level has further sub-levels numbered 0 (least
/// informative) to 99 (most informative).
/// - Each logger has a severity level set associated with it. When a
/// message is logged, it is output only if it is logged at a level equal
/// to the logger severity level or greater, e.g. if the logger's severity
/// is WARN, only messages logged at WARN, ERROR or FATAL will be output.
///
/// \section LoggingApiLoggerNames Kea Logger Names
/// Within Kea, the root logger root logger is given the name of the
/// program (via the stand-alone function setRootLoggerName()). Other loggers
/// are children of the root logger and are named "<program>.<sublogger>".
/// This name appears in logging output, allowing users to identify both
/// the Kea program and the component within the program that generated
/// the message.
///
/// When creating a logger, the abbreviated name "<sublogger>" can be used;
/// the program name will be prepended to it when the logger is created.
/// In this way, individual libraries can have their own loggers without
/// worrying about the program in which they are used, but:
/// - The origin of the message will be clearly identified.
/// - The same component can have different options (e.g. logging severity)
/// in different programs at the same time.
///
/// \section LoggingApiLoggingMessages Logging Messages
/// Instead of embedding the text of messages within the code, each message
/// is referred to using a symbolic name. The logging code uses this name as
/// a key in a dictionary from which the message text is obtained. Such a
/// system allows for the optional replacement of message text at run time.
/// More details about the message dictionary (and the compiler used to create
/// the symbol definitions) can be found in other modules in the src/lib/log
/// directory.
///
/// \section LoggingApiImplementationIssues Implementation Issues
/// Owing to the way that the logging is implemented, notably that loggers can
/// be declared as static external objects, there is a restriction on the
/// length of the name of a logger component (i.e. the length of
/// the string passed to the Logger constructor) to a maximum of 31 characters.
/// There is no reason for this particular value other than limiting the amount
/// of memory used. It is defined by the constant Logger::MAX_LOGGER_NAME_SIZE,
/// and can be made larger (or smaller) if so desired.
class LoggerImpl; // Forward declaration of the implementation class
/// \brief Bad Interprocess Sync
///
/// Exception thrown if a bad InterprocessSync object (such as null) is
/// used.
class BadInterprocessSync : public isc::Exception {
public:
BadInterprocessSync(const char* file, size_t line, const char* what) :
isc::Exception(file, line, what)
{}
};
/// \brief Logger Name Error
///
/// Exception thrown if a logger name is too short or too long.
class LoggerNameError : public isc::Exception {
public:
LoggerNameError(const char* file, size_t line, const char* what) :
isc::Exception(file, line, what)
{}
};
/// \brief Logger Name is null
///
/// Exception thrown if a logger name is null
class LoggerNameNull : public isc::Exception {
public:
LoggerNameNull(const char* file, size_t line, const char* what) :
isc::Exception(file, line, what)
{}
};
/// \brief Logging Not Initialized
///
/// Exception thrown if an attempt is made to access a logging function
/// if the logging system has not been initialized.
class LoggingNotInitialized : public isc::Exception {
public:
LoggingNotInitialized(const char* file, size_t line, const char* what) :
isc::Exception(file, line, what)
{}
};
/// \brief Logger Class
///
/// This class is the main class used for logging. Use comprises:
///
/// 1. Constructing a logger by instantiating it with a specific name. (If the
/// same logger is in multiple functions within a file, overhead can be
/// minimized by declaring it as a file-wide static variable.)
/// 2. Using the error(), info() etc. methods to log an error. (However, it is
/// recommended to use the LOG_ERROR, LOG_INFO etc. macros defined in macros.h.
/// These will avoid the potentially-expensive evaluation of arguments if the
/// severity is such that the message will be suppressed.)
class Logger {
public:
/// Maximum size of a logger name
static const size_t MAX_LOGGER_NAME_SIZE = 31;
/// \brief Constructor
///
/// Creates/attaches to a logger of a specific name.
///
/// \param name Name of the logger. If the name is that of the root name,
/// this creates an instance of the root logger; otherwise it creates a
/// child of the root logger.
///
/// \note The name of the logger may be no longer than MAX_LOGGER_NAME_SIZE
/// else the program will throw an exception. This restriction allows
/// loggers to be declared statically: the name is stored in a fixed-size
/// array to avoid the need to allocate heap storage during program
/// initialization (which causes problems on some operating systems).
///
/// \note Note also that there is no constructor taking a std::string. This
/// minimizes the possibility of initializing a static logger with a
/// string, so leading to problems mentioned above.
Logger(const char* name) : loggerptr_(0), initialized_(false) {
// Validate the name of the logger.
if (name) {
// Name not null, is it too short or too long?
size_t namelen = std::strlen(name);
if ((namelen == 0) || (namelen > MAX_LOGGER_NAME_SIZE)) {
isc_throw(LoggerNameError, "'" << name << "' is not a valid "
<< "name for a logger: valid names must be between 1 "
<< "and " << MAX_LOGGER_NAME_SIZE << " characters in "
<< "length");
}
} else {
isc_throw(LoggerNameNull, "logger names may not be null");
}
// Do the copy, ensuring a trailing null in all cases.
std::strncpy(name_, name, MAX_LOGGER_NAME_SIZE);
name_[MAX_LOGGER_NAME_SIZE] = '\0';
}
/// \brief Destructor
virtual ~Logger();
/// \brief Version
static std::string getVersion();
/// \brief The formatter used to replace placeholders
typedef isc::log::Formatter<Logger> Formatter;
/// \brief Get Name of Logger
///
/// \return The full name of the logger (including the root name)
virtual std::string getName();
/// \brief Set Severity Level for Logger
///
/// Sets the level at which this logger will log messages. If none is set,
/// the level is inherited from the parent.
///
/// \param severity Severity level to log
/// \param dbglevel If the severity is DEBUG, this is the debug level.
/// This can be in the range 1 to 100 and controls the verbosity. A value
/// outside these limits is silently coerced to the nearest boundary.
virtual void setSeverity(isc::log::Severity severity, int dbglevel = 1);
/// \brief Get Severity Level for Logger
///
/// \return The current logging level of this logger. In most cases though,
/// the effective logging level is what is required.
virtual isc::log::Severity getSeverity();
/// \brief Get Effective Severity Level for Logger
///
/// \return The effective severity level of the logger. This is the same
/// as getSeverity() if the logger has a severity level set, but otherwise
/// is the severity of the parent.
virtual isc::log::Severity getEffectiveSeverity();
/// \brief Return DEBUG Level
///
/// \return Current setting of debug level. This is returned regardless of
/// whether the severity is set to debug.
virtual int getDebugLevel();
/// \brief Get Effective Debug Level for Logger
///
/// \return The effective debug level of the logger. This is the same
/// as getDebugLevel() if the logger has a debug level set, but otherwise
/// is the debug level of the parent.
virtual int getEffectiveDebugLevel();
/// \brief Returns if Debug Message Should Be Output
///
/// \param dbglevel Level for which debugging is checked. Debugging is
/// enabled only if the logger has DEBUG enabled and if the dbglevel
/// checked is less than or equal to the debug level set for the logger.
virtual bool isDebugEnabled(int dbglevel = MIN_DEBUG_LEVEL);
/// \brief Is INFO Enabled?
virtual bool isInfoEnabled();
/// \brief Is WARNING Enabled?
virtual bool isWarnEnabled();
/// \brief Is ERROR Enabled?
virtual bool isErrorEnabled();
/// \brief Is FATAL Enabled?
virtual bool isFatalEnabled();
/// \brief Output Debug Message
///
/// \param dbglevel Debug level, ranging between 0 and 99. Higher numbers
/// are used for more verbose output.
/// \param ident Message identification.
Formatter debug(int dbglevel, const MessageID& ident);
/// \brief Output Informational Message
///
/// \param ident Message identification.
Formatter info(const MessageID& ident);
/// \brief Output Warning Message
///
/// \param ident Message identification.
Formatter warn(const MessageID& ident);
/// \brief Output Error Message
///
/// \param ident Message identification.
Formatter error(const MessageID& ident);
/// \brief Output Fatal Message
///
/// \param ident Message identification.
Formatter fatal(const MessageID& ident);
/// \brief Replace the interprocess synchronization object
///
/// If this method is called with null as the argument, it throws a
/// BadInterprocessSync exception.
///
/// \note This method is intended to be used only within this log library
/// and its tests. Normal application shouldn't use it (in fact,
/// normal application shouldn't even be able to instantiate
/// InterprocessSync objects).
///
/// \param sync The logger uses this synchronization object for
/// synchronizing output of log messages. It should be deletable and
/// the ownership is transferred to the logger. If null is passed,
/// a BadInterprocessSync exception is thrown.
void setInterprocessSync(isc::log::interprocess::InterprocessSync* sync);
/// @brief Check if this logger has an appender of the given type.
///
/// @param destination the appender type to be checked: console, file or syslog
///
/// @return true if an appender of the given type is found, false otherwise
bool hasAppender(OutputOption::Destination const destination);
/// \brief Equality
///
/// Check if two instances of this logger refer to the same stream.
///
/// \return true if the logger objects are instances of the same logger.
bool operator==(Logger& other);
private:
friend class isc::log::Formatter<Logger>;
/// \brief Raw output function
///
/// This is used by the formatter to output formatted output.
///
/// \param severity Severity of the message being output.
/// \param message Text of the message to be output.
void output(const Severity& severity, const std::string& message);
/// \brief Copy Constructor
///
/// Disabled (marked private) as it makes no sense to copy the logger -
/// just create another one of the same name.
Logger(const Logger&);
/// \brief Assignment Operator
///
/// Disabled (marked private) as it makes no sense to copy the logger -
/// just create another one of the same name.
Logger& operator=(const Logger&);
/// \brief Initialize Implementation
///
/// Returns the logger pointer. If not yet set, the implementation class is
/// initialized.
///
/// The main reason for this is to allow loggers to be declared statically
/// before the underlying logging system is initialized. However, any
/// attempt to access a logging method on any logger before initialization -
/// regardless of whether is is statically or automatically declared - will
/// cause a "LoggingNotInitialized" exception to be thrown.
///
/// \return Returns pointer to implementation
LoggerImpl* getLoggerPtr();
/// \brief Initialize Underlying Implementation and Set loggerptr_
void initLoggerImpl();
///< Pointer to underlying logger
LoggerImpl* loggerptr_;
///< Copy of the logger name
char name_[MAX_LOGGER_NAME_SIZE + 1];
///< Mutex to protect the internal state
std::mutex mutex_;
///< Flag which indicates if logger is initialized
std::atomic<bool> initialized_;
};
} // namespace log
} // namespace isc
#endif // LOGGER_H
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