Custom ASP.NET Health Monitoring Provider Example

The code example in this topic demonstrates how to implement a custom ASP.NET health monitoring provider. For details about how to use this example and links to the other files, see How to: Implement the Health Monitoring Custom Provider Example.

The following code example shows how to derive from the BufferedWebEventProvider class to create a custom provider that writes specified health monitoring event information to a local file. Before you build the example, change the logFilePath = "C:\test\log.doc" assignment so that the logFilePath variable points to a folder for which your program has write and create access rights.

Imports Microsoft.VisualBasic
Imports System
Imports System.Text
Imports System.IO
Imports System.Web.Management
Imports System.Collections.Generic
Imports System.Collections.Specialized
Imports System.Web


Namespace Samples.AspNet.Management

    ' Implements a custom event provider. 


    Public Class SampleBufferedEventProvider
        Inherits BufferedWebEventProvider

        ' The local path of the file where 
        ' to store event information. 
        Private logFilePath As String = String.Empty

        ' Holds custom information. 
        Private customInfo As New StringBuilder()

        Private providerName, buffer, bufMode As String 



        ' Initializes the provider. 
        Public Overrides Sub Initialize(ByVal name As String, ByVal config As NameValueCollection)
            MyBase.Initialize(name, config)

            'Define the log local file location.
            logFilePath = "C:\test\log.doc"

            customInfo = New StringBuilder()

            providerName = name
            buffer = config.Get("buffer")
            bufMode = config.Get("bufferMode")

            customInfo.AppendLine( _
            String.Format("Provider name: {0}", providerName))
            customInfo.AppendLine( _
            String.Format("Buffering: {0}", buffer))
            customInfo.AppendLine( _
            String.Format("Buffering modality: {0}", BufferMode))
        End Sub 'Initialize




        ' Processes the incoming events. 
        ' This method performs custom processing and, if 
        ' buffering is enabled, it calls the base.ProcessEvent 
        ' to buffer the event information. 
        Public Overrides Sub ProcessEvent( _
        ByVal eventRaised As WebBaseEvent)

            If UseBuffering Then 
                ' Buffering enabled, call the base event to 
                ' buffer event information. 
                MyBase.ProcessEvent(eventRaised)
            Else 
                ' Buffering disabled, store event information 
                ' immediately.
                customInfo.AppendLine(String.Format( _
                "{0}", eventRaised.Message))
                ' Store the information in the specified file.
                StoreToFile(customInfo, logFilePath, FileMode.Append)
            End If 
        End Sub 'ProcessEvent


        ' Processes the messages that have been buffered. 
        ' It is called by the ASP.NET when the flushing of  
        ' the buffer is required according to the parameters  
        ' defined in the <bufferModes> element of the  
        ' <healthMonitoring> configuration section. 
        Public Overrides Sub ProcessEventFlush( _
        ByVal flushInfo As WebEventBufferFlushInfo)

            ' Customize event information to be logged. 
            customInfo.AppendLine( _
            "SampleEventLogWebEventProvider buffer flush.")

            customInfo.AppendLine(String.Format( _
            "NotificationType: {0}", flushInfo.NotificationType))

            customInfo.AppendLine(String.Format( _
            "EventsInBuffer: {0}", flushInfo.EventsInBuffer))

            customInfo.AppendLine(String.Format( _
            "EventsDiscardedSinceLastNotification: {0}", _
            flushInfo.EventsDiscardedSinceLastNotification))


            ' Read each buffered event and send it to the 
            ' Log. 
            Dim eventRaised As WebBaseEvent
            For Each eventRaised In flushInfo.Events
                customInfo.AppendLine(eventRaised.ToString())
            Next eventRaised
            ' Store the information in the specified file.
            StoreToFile(customInfo, logFilePath, FileMode.Append)

        End Sub 'ProcessEventFlush


        ' Performs standard shutdown. 
        Public Overrides Sub Shutdown()
            ' Here you need the code that performs 
            ' those tasks required before shutting  
            ' down the provider. 
            ' Flush the buffer, if needed.
            Flush()
        End Sub 'Shutdown


        ' Store event information in a local file. 
        Private Sub StoreToFile( _
        ByVal [text] As StringBuilder, _
        ByVal filePath As String, ByVal mode As FileMode)
            Dim writeBlock As Integer 
            Dim startIndex As Integer 

            Try

                writeBlock = 256
                startIndex = 0

                ' Open or create the local file  
                ' to store the event information. 
                Dim fs As New FileStream(filePath, mode, FileAccess.Write)

                ' Lock the file for writing.
                fs.Lock(startIndex, writeBlock)

                ' Create a stream writer 
                Dim writer As New StreamWriter(fs)

                ' Set the file pointer to the current  
                ' position to keep adding data to it.  
                ' If you want to rewrite the file use  
                ' the following statement instead. 
                ' writer.BaseStream.Seek (0, SeekOrigin.Begin);
                writer.BaseStream.Seek(0, SeekOrigin.Current)

                'If the file already exists it must not  
                ' be write protected otherwise   
                ' the following write operation fails silently.
                writer.Write([text].ToString())

                ' Update the underlying file
                writer.Flush()

                ' Unlock the file for other processes.
                fs.Unlock(startIndex, writeBlock)

                ' Close the stream writer and the underlying file     
                writer.Close()

                fs.Close()
            Catch e As Exception
                Throw New Exception("SampleEventProvider.StoreToFile: " + e.ToString())
            End Try 
        End Sub 'StoreToFile
    End Class 'SampleBufferedEventProvider

End Namespace

using System;
using System.Text;
using System.IO;
using System.Web.Management;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Web;


namespace Samples.AspNet.Management
{
    // Implements a custom event provider. 
    public class SampleBufferedEventProvider :
        BufferedWebEventProvider
    {

        // The local path of the file where 
        // to store event information. 
        private string logFilePath = string.Empty;

        // Holds custom information. 
        private StringBuilder customInfo =
            new StringBuilder();

        private string providerName, buffer, bufferMode;


        // Initializes the provider. 
        public override void Initialize(string name,
         NameValueCollection config)
        {
            base.Initialize(name, config);

            logFilePath = @"C:\test\log.doc";

            customInfo = new StringBuilder();

            providerName = name;
            buffer = config.Get("buffer");
            bufferMode = config.Get("bufferMode");


            customInfo.AppendLine(string.Format(
                "Provider name: {0}", providerName));
            customInfo.AppendLine(string.Format(
                            "Buffering: {0}", buffer));
            customInfo.AppendLine(string.Format(
                            "Buffering modality: {0}", bufferMode));

        }


        // Processes the incoming events. 
        // This method performs custom processing and, if 
        // buffering is enabled, it calls the base.ProcessEvent 
        // to buffer the event information. 
        public override void ProcessEvent(
            WebBaseEvent eventRaised)
        {

            if (UseBuffering)
                // Buffering enabled, call the base event to 
                // buffer event information. 
                base.ProcessEvent(eventRaised);
            else
            {
                // Buffering disabled, store event info 
                // immediately.
                customInfo.AppendLine(string.Format(
                                   "{0}", eventRaised.Message));

                // Store the information in the specified file.
                StoreToFile(customInfo, logFilePath, FileMode.Append);

            }
        }

        // Processes the messages that have been buffered. 
        // It is called by the ASP.NET when the flushing of  
        // the buffer is required according to the parameters  
        // defined in the <bufferModes> element of the  
        // <healthMonitoring> configuration section. 
        public override void ProcessEventFlush(
            WebEventBufferFlushInfo flushInfo)
        {

            // Customize event information to be logged.
            customInfo.AppendLine(
                "SampleEventLogWebEventProvider buffer flush.");

            customInfo.AppendLine(
                string.Format("NotificationType: {0}",
                flushInfo.NotificationType));

            customInfo.AppendLine(
                string.Format("EventsInBuffer: {0}",
                flushInfo.EventsInBuffer));

            customInfo.AppendLine(
                string.Format("EventsDiscardedSinceLastNotification: {0}",
                flushInfo.EventsDiscardedSinceLastNotification));


            // Read each buffered event and send it to the 
            // Log. 
            foreach (WebBaseEvent eventRaised in flushInfo.Events)
                customInfo.AppendLine(eventRaised.ToString());

            // Store the information in the specified file.
            StoreToFile(customInfo, logFilePath, FileMode.Append);
        }

        // Performs standard shutdown. 
        public override void Shutdown()
        {
            // Here you need the code that performs 
            // those tasks required before shutting  
            // down the provider. 

            // Flush the buffer, if needed.
            Flush();
        }

        // Store event information in a local file. 
        private void StoreToFile(StringBuilder text,
            string filePath, FileMode mode)
        {
            int writeBlock;
            int startIndex;

            try
            {

                writeBlock = 256;
                startIndex = 0;

                // Open or create the local file  
                // to store the event information.
                FileStream fs = new FileStream(filePath,
                    mode, FileAccess.Write);

                // Lock the file for writing.
                fs.Lock(startIndex, writeBlock);

                // Create a stream writer
                StreamWriter writer = new StreamWriter(fs);

                // Set the file pointer to the current  
                // position to keep adding data to it.  
                // If you want to rewrite the file use  
                // the following statement instead. 
                // writer.BaseStream.Seek (0, SeekOrigin.Begin);
                writer.BaseStream.Seek(0, SeekOrigin.Current);

                //If the file already exists it must not  
                // be write protected otherwise   
                // the following write operation fails silently.
                writer.Write(text.ToString());

                // Update the underlying file
                writer.Flush();

                // Unlock the file for other processes.
                fs.Unlock(startIndex, writeBlock);

                // Close the stream writer and the underlying file     
                writer.Close();

                fs.Close();
            }
            catch (Exception e)
            {
                throw new Exception(
                    "SampleEventProvider.StoreToFile: "
                    + e.ToString());
            }
        }

    }

}

How to: Implement the Health Monitoring Custom Provider Example