logger.hpp

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/* Copyright (C) 2003 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

#ifndef Logger_H
#define Logger_H

#include <ndb_global.h>
#include <BaseString.hpp>

#define MAX_LOG_MESSAGE_SIZE 1024

class LogHandler;
class LogHandlerList;

/**
 * Logger should be used whenver you need to log a message like
 * general information or debug messages. By creating/adding different
 * log handlers, a single log message can be sent to 
 * different outputs (stdout, file or syslog).
 * 
 * Each log entry is created with a log level (or severity) which is 
 * used to identity the type of the entry, e.g., if it is a debug 
 * or an error message.
 * 
 * Example of a log entry:
 *
 *  09:17:39 2002-03-13 [myLogger] INFO -- Local checkpoint started.
 *
 * HOW TO USE
 *
 * 1) Create a new instance of the Logger.
 *
 *    Logger myLogger = new Logger();
 *
 * 2) Add the log handlers that you want, i.e., where the log entries 
 *    should be written/shown.
 *
 *    myLogger->createConsoleHandler();  // Output to console/stdout
 *    myLogger->addHandler(new FileLogHandler("mylog.txt")); // use mylog.txt
 *
 *  3) Tag each log entry with a category/name.
 *
 *    myLogger->setCategory("myLogger");
 *
 * 4) Start log messages.
 *    
 *     myLogger->alert("T-9 to lift off");
 *     myLogger->info("Here comes the sun, la la"); 
 *     myLogger->debug("Why does this not work!!!, We should not be here...")
 *
 * 5) Log only debug messages.
 *
 *    myLogger->enable(Logger::LL_DEBUG);
 *
 * 6) Log only ALERTS and ERRORS.
 *
 *    myLogger->enable(Logger::LL_ERROR, Logger::LL_ALERT);
 * 
 * 7) Do not log any messages.
 *
 *    myLogger->disable(Logger::LL_ALL);
 *
 *
 * LOG LEVELS (Matches the severity levels of syslog)
 * <pre>
 *
 *  ALERT           A condition  that  should  be  corrected
 *                  immediately,  such as a corrupted system
 *                  database.
 *
 *  CRITICAL        Critical conditions, such as hard device
 *                  errors.
 *
 *  ERROR           Errors.
 *
 *  WARNING         Warning messages.
 *
 *  INFO            Informational messages.
 *
 *  DEBUG           Messages that contain  information  nor-
 *                  mally  of use only when debugging a pro-
 *                  gram.
 * </pre>
 *
 * @version #@ $Id: Logger.hpp,v 1.7 2003/09/01 10:15:53 innpeno Exp $
 */
class Logger
{
public:
  /** The log levels. NOTE: Could not use the name LogLevel since 
   * it caused conflicts with another class.
   */
  enum LoggerLevel {LL_ON, LL_DEBUG, LL_INFO, LL_WARNING, LL_ERROR,
		    LL_CRITICAL, LL_ALERT, LL_ALL};
  
  /**
   * String representation of the the log levels.
   */
  static const char* LoggerLevelNames[];

  /**
   * Default constructor.
   */
  Logger();

  /**
   * Destructor.
   */
  virtual ~Logger();
  
  /**
   * Set a category/name that each log entry will have.
   *
   * @param pCategory the category.
   */
  void setCategory(const char* pCategory);

  /**
   * Create a default handler that logs to the console/stdout.
   *
   * @return true if successful.
   */
  bool createConsoleHandler();

  /**
   * Remove the default console handler.
   */
  void removeConsoleHandler();

  /**
   * Create a default handler that logs to a file called logger.log.
   *
   * @return true if successful.
   */
  bool createFileHandler();

  /**
   * Remove the default file handler.
   */
  void removeFileHandler();

  /**
   * Create a default handler that logs to the syslog.
   *
   * On OSE a ConsoleHandler will be created since there is no syslog support.
   *
   * @return true if successful.
   */
  bool createSyslogHandler();	

  /**
   * Remove the default syslog handler.
   */
  void removeSyslogHandler();

  /**
   * Add a new log handler.
   *
   * @param pHandler a log handler.
   * @return true if successful.
   */
  bool addHandler(LogHandler* pHandler);

  /**
   * Add a new handler
   *
   * @param logstring string describing the handler to add
   * @param err OS errno in event of error
   * @param len max length of errStr buffer
   * @param errStr logger error string in event of error
   */
  bool addHandler(const BaseString &logstring, int *err, int len, char* errStr);

  /**
   * Remove a log handler.
   *
   * @param pHandler log handler to remove.
   * @return true if successful.
   */
  bool removeHandler(LogHandler* pHandler);

  /**
   * Remove all log handlers.
   */
  void removeAllHandlers();

  /**
   * Returns true if the specified log level is enabled.
   *
   * @return true if enabled.
   */
  bool isEnable(LoggerLevel logLevel) const; 

  /**
   * Enable the specified log level.
   *
   * @param logLevel the loglevel to enable.
   */
  void enable(LoggerLevel logLevel);

  /**
   * Enable log levels.
   *
   * @param fromLogLevel enable from log level.
   * @param toLogLevel enable to log level.
   */
  void enable (LoggerLevel fromLogLevel, LoggerLevel toLogLevel);

  /**
   * Disable log level.
   *
   * @param logLevel disable log level.
   */
  void disable(LoggerLevel logLevel);

  /**
   * Log an alert message.
   *
   * @param pMsg the message.
   */
  virtual void alert(const char* pMsg, ...) const;
  virtual void alert(BaseString &pMsg) const { alert(pMsg.c_str()); };
  
  /**
   * Log a critical message.
   *
   * @param pMsg the message.
   */
  virtual void critical(const char* pMsg, ...) const;
  virtual void critical(BaseString &pMsg) const { critical(pMsg.c_str()); };

  /**
   * Log an error message.
   *
   * @param pMsg the message.
   */
  virtual void error(const char* pMsg, ...) const;
  virtual void error(BaseString &pMsg) const { error(pMsg.c_str()); };

  /**
   * Log a warning message.
   *
   * @param pMsg the message.
   */
  virtual void warning(const char* pMsg, ...) const;
  virtual void warning(BaseString &pMsg) const { warning(pMsg.c_str()); };

  /**
   * Log an info message.
   *
   * @param pMsg the message.
   */
  virtual void info(const char* pMsg, ...) const;
  virtual void info(BaseString &pMsg) const { info(pMsg.c_str()); };

  /**
   * Log a debug message.
   *
   * @param pMsg the message.
   */
  virtual void debug(const char* pMsg, ...) const;
  virtual void debug(BaseString &pMsg) const { debug(pMsg.c_str()); };

protected:

  void log(LoggerLevel logLevel, const char* msg, va_list ap) const;

private:
  /** Prohibit */
  Logger(const Logger&);
  Logger operator = (const Logger&);
  bool operator == (const Logger&);

  STATIC_CONST( MAX_LOG_LEVELS = 8 );

  bool m_logLevels[MAX_LOG_LEVELS];
  
  LogHandlerList* m_pHandlerList;
  const char* m_pCategory;
  /* Default handlers */
  LogHandler* m_pConsoleHandler;
  LogHandler* m_pFileHandler;
  LogHandler* m_pSyslogHandler;
};

#endif