localsyslogappender.cs

精通SQL Server2005项目开发

		public SyslogFacility Facility
		{
			get { return m_facility; }
			set { m_facility = value; }
		}
		
		#endregion // Public Instance Properties

		/// <summary>
		/// Add a mapping of level to severity
		/// </summary>
		/// <param name="mapping">The mapping to add</param>
		/// <remarks>
		/// <para>
		/// Adds a <see cref="LevelSeverity"/> to this appender.
		/// </para>
		/// </remarks>
		public void AddMapping(LevelSeverity mapping)
		{
			m_levelMapping.Add(mapping);
		}

		#region IOptionHandler Implementation

		/// <summary>
		/// Initialize the appender based on the options set.
		/// </summary>
		/// <remarks>
		/// <para>
		/// This is part of the <see cref="IOptionHandler"/> delayed object
		/// activation scheme. The <see cref="ActivateOptions"/> method must 
		/// be called on this object after the configuration properties have
		/// been set. Until <see cref="ActivateOptions"/> is called this
		/// object is in an undefined state and must not be used. 
		/// </para>
		/// <para>
		/// If any of the configuration properties are modified then 
		/// <see cref="ActivateOptions"/> must be called again.
		/// </para>
		/// </remarks>
		public override void ActivateOptions()
		{
			base.ActivateOptions();
			
			m_levelMapping.ActivateOptions();

			string identString = m_identity;
			if (identString == null)
			{
				// Set to app name by default
				identString = SystemInfo.ApplicationFriendlyName;
			}

			// create the native heap ansi string. Note this is a copy of our string
			// so we do not need to hold on to the string itself, holding on to the
			// handle will keep the heap ansi string alive.
			m_handleToIdentity = Marshal.StringToHGlobalAnsi(identString);

			// open syslog
			openlog(m_handleToIdentity, 1, m_facility);
		}

		#endregion // IOptionHandler Implementation

		#region AppenderSkeleton Implementation

		/// <summary>
		/// This method is called by the <see cref="AppenderSkeleton.DoAppend(LoggingEvent)"/> method.
		/// </summary>
		/// <param name="loggingEvent">The event to log.</param>
		/// <remarks>
		/// <para>
		/// Writes the event to a remote syslog daemon.
		/// </para>
		/// <para>
		/// The format of the output will depend on the appender's layout.
		/// </para>
		/// </remarks>
		protected override void Append(LoggingEvent loggingEvent) 
		{
			int priority = GeneratePriority(m_facility, GetSeverity(loggingEvent.Level));
			string message = RenderLoggingEvent(loggingEvent);

			// Call the local libc syslog method
			// The second argument is a printf style format string
			syslog(priority, "%s", message);
		}

		/// <summary>
		/// Close the syslog when the appender is closed
		/// </summary>
		/// <remarks>
		/// <para>
		/// Close the syslog when the appender is closed
		/// </para>
		/// </remarks>
		protected override void OnClose()
		{
			base.OnClose();

			try
			{
				// close syslog
				closelog();
			}
			catch(DllNotFoundException)
			{
				// Ignore dll not found at this point
			}
		
			if (m_handleToIdentity != IntPtr.Zero)
			{
				// free global ident
				Marshal.FreeHGlobal(m_handleToIdentity);
			}
		}

		/// <summary>
		/// This appender requires a <see cref="AppenderSkeleton.Layout"/> to be set.
		/// </summary>
		/// <value><c>true</c></value>
		/// <remarks>
		/// <para>
		/// This appender requires a <see cref="AppenderSkeleton.Layout"/> to be set.
		/// </para>
		/// </remarks>
		override protected bool RequiresLayout
		{
			get { return true; }
		}

		#endregion // AppenderSkeleton Implementation

		#region Protected Members

		/// <summary>
		/// Translates a log4net level to a syslog severity.
		/// </summary>
		/// <param name="level">A log4net level.</param>
		/// <returns>A syslog severity.</returns>
		/// <remarks>
		/// <para>
		/// Translates a log4net level to a syslog severity.
		/// </para>
		/// </remarks>
		virtual protected SyslogSeverity GetSeverity(Level level)
		{
			LevelSeverity levelSeverity = m_levelMapping.Lookup(level) as LevelSeverity;
			if (levelSeverity != null)
			{
				return levelSeverity.Severity;
			}

			//
			// Fallback to sensible default values
			//

			if (level >= Level.Alert) 
			{
				return SyslogSeverity.Alert;
			} 
			else if (level >= Level.Critical) 
			{
				return SyslogSeverity.Critical;
			} 
			else if (level >= Level.Error) 
			{
				return SyslogSeverity.Error;
			} 
			else if (level >= Level.Warn) 
			{
				return SyslogSeverity.Warning;
			} 
			else if (level >= Level.Notice) 
			{
				return SyslogSeverity.Notice;
			} 
			else if (level >= Level.Info) 
			{
				return SyslogSeverity.Informational;
			} 
			// Default setting
			return SyslogSeverity.Debug;
		}

		#endregion // Protected Members

		#region Public Static Members

		/// <summary>
		/// Generate a syslog priority.
		/// </summary>
		/// <param name="facility">The syslog facility.</param>
		/// <param name="severity">The syslog severity.</param>
		/// <returns>A syslog priority.</returns>
		private static int GeneratePriority(SyslogFacility facility, SyslogSeverity severity)
		{
			return ((int)facility * 8) + (int)severity;
		}

		#endregion // Public Static Members

		#region Private Instances Fields

		/// <summary>
		/// The facility. The default facility is <see cref="SyslogFacility.User"/>.
		/// </summary>
		private SyslogFacility m_facility = SyslogFacility.User;

		/// <summary>
		/// The message identity
		/// </summary>
		private string m_identity;

		/// <summary>
		/// Marshaled handle to the identity string. We have to hold on to the
		/// string as the <c>openlog</c> and <c>syslog</c> APIs just hold the
		/// pointer to the ident and dereference it for each log message.
		/// </summary>
		private IntPtr m_handleToIdentity = IntPtr.Zero;

		/// <summary>
		/// Mapping from level object to syslog severity
		/// </summary>
		private LevelMapping m_levelMapping = new LevelMapping();

		#endregion // Private Instances Fields

		#region External Members
		
		/// <summary>
		/// Open connection to system logger.
		/// </summary>
		[DllImport("libc")]
		private static extern void openlog(IntPtr ident, int option, SyslogFacility facility);

		/// <summary>
		/// Generate a log message.
		/// </summary>
		/// <remarks>
		/// <para>
		/// The libc syslog method takes a format string and a variable argument list similar
		/// to the classic printf function. As this type of vararg list is not supported
		/// by C# we need to specify the arguments explicitly. Here we have specified the
		/// format string with a single message argument. The caller must set the format 
		/// string to <c>"%s"</c>.
		/// </para>
		/// </remarks>
		[DllImport("libc", CharSet=CharSet.Ansi, CallingConvention=CallingConvention.Cdecl)]
		private static extern void syslog(int priority, string format, string message);

		/// <summary>
		/// Close descriptor used to write to system logger.
		/// </summary>
		[DllImport("libc")]
		private static extern void closelog();

		#endregion // External Members

		#region LevelSeverity LevelMapping Entry

		/// <summary>
		/// A class to act as a mapping between the level that a logging call is made at and
		/// the syslog severity that is should be logged at.
		/// </summary>
		/// <remarks>
		/// <para>
		/// A class to act as a mapping between the level that a logging call is made at and
		/// the syslog severity that is should be logged at.
		/// </para>
		/// </remarks>
		public class LevelSeverity : LevelMappingEntry
		{
			private SyslogSeverity m_severity;

			/// <summary>
			/// The mapped syslog severity for the specified level
			/// </summary>
			/// <remarks>
			/// <para>
			/// Required property.
			/// The mapped syslog severity for the specified level
			/// </para>
			/// </remarks>
			public SyslogSeverity Severity
			{
				get { return m_severity; }
				set { m_severity = value; }
			}
		}

		#endregion // LevelSeverity LevelMapping Entry
	}
}

#endif