Elmah Exception Logging with Azure

Summary

If you have an ASP.Net project mapped to an Azure worker role, then Elmah is a great exception handling framework for providing near code-less, world class exception handling for your project. Read on for a step-by-step guide.

• Create an Azure web role
• Reference the Elmah dll in your project
• In its web.config file, in the configSections node under the configuration node, add the following section:

• <sectionGroup name="elmah">
        <!-- NOTE! If you are using ASP.NET 1.x then remove the
            requirePermission="false" attribute from the section
            elements below as those are only needed for
            partially trusted applications in ASP.NET 2.0 -->
        <section name="security" requirePermission="false" type="Elmah.SecuritySectionHandler, Elmah"/>
        <section name="errorLog" requirePermission="false" type="Elmah.ErrorLogSectionHandler, Elmah" />
        <section name="errorMail" requirePermission="false" type="Elmah.ErrorMailSectionHandler, Elmah" />
        <section name="errorFilter" requirePermission="false" type="Elmah.ErrorFilterSectionHandler, Elmah"/>
        <section name="errorTweet" requirePermission="false" type="Elmah.ErrorTweetSectionHandler, Elmah"/>
  </sectionGroup>

• Add the elmah node right after configSections

• <elmah>
  
      <security allowRemoteAccess="1" />
      <errorLog type="Elmah.SqlErrorLog, Elmah"
              connectionString="data source=server;initial catalog=databaseuser id=user;password=password;multipleactiveresultsets=True;" />
  
      <!--<errorFilter>
        <test>
          <jscript>
            <expression>
              <![CDATA[
                      // @assembly mscorlib
                      // @assembly System.Web, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
                      // @import System.IO
                      // @import System.Web
  
                      HttpStatusCode == 404
                      || BaseException instanceof FileNotFoundException 
                      || BaseException instanceof HttpRequestValidationException
                      /* Using RegExp below (see http://msdn.microsoft.com/en-us/library/h6e2eb7w.aspx) */
                      || Context.Request.UserAgent.match(/crawler/i)                      
                      || Context.Request.ServerVariables['REMOTE_ADDR'] == '127.0.0.1' // IPv4 only
                      ]]>
            </expression>
          </jscript>
        </test>
      </errorFilter>-->
    </elmah>

• Under the system.web section add the following modules and handlers

• <httpHandlers>
        <add verb="POST,GET,HEAD" path="elmah.axd" type="Elmah.ErrorLogPageFactory, Elmah"/>
      </httpHandlers>
      <httpModules>
        <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah"/>
        <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah"/>
        <add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah"/>
      </httpModules>

• Under the system.webServer section, add the following modules and handlers

• <handlers>
        <add name="Elmah" verb="POST,GET,HEAD" path="elmah.axd" preCondition="integratedMode" type="Elmah.ErrorLogPageFactory, Elmah"/>
      </handlers>
  
      <modules runAllManagedModulesForAllRequests="true">
        <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah"/>
        <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah"/>
        <add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah"/>
      </modules>

• Create the logging table in your database by running the following SQL

• --~Changing index [dbo].[ELMAH_Error].PK_ELMAH_Error to a clustered index.  You may want to pick a different index to cluster on.
  SET ANSI_NULLS ON
  SET QUOTED_IDENTIFIER ON
  IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ELMAH_Error]') AND type in (N'U'))
  BEGIN
  CREATE TABLE [dbo].[ELMAH_Error](
      [ErrorId] [uniqueidentifier] NOT NULL,
      [Application] [nvarchar](60) NOT NULL,
      [Host] [nvarchar](50) NOT NULL,
      [Type] [nvarchar](100) NOT NULL,
      [Source] [nvarchar](60) NOT NULL,
      [Message] [nvarchar](500) NOT NULL,
      [User] [nvarchar](50) NOT NULL,
      [StatusCode] [int] NOT NULL,
      [TimeUtc] [datetime] NOT NULL,
      [Sequence] [int] IDENTITY(1,1) NOT NULL,
      [AllXml] [nvarchar](max) NOT NULL,
   CONSTRAINT [PK_ELMAH_Error] PRIMARY KEY CLUSTERED 
  (
      [ErrorId] ASC
  )WITH (STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF)
  )
  END
  
  IF NOT EXISTS (SELECT * FROM sys.indexes WHERE object_id = OBJECT_ID(N'[dbo].[ELMAH_Error]') AND name = N'IX_ELMAH_Error_App_Time_Seq')
  CREATE NONCLUSTERED INDEX [IX_ELMAH_Error_App_Time_Seq] ON [dbo].[ELMAH_Error] 
  (
      [Application] ASC,
      [TimeUtc] DESC,
      [Sequence] DESC
  )WITH (STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF)
  GO
  IF NOT EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[DF_ELMAH_Error_ErrorId]') AND type = 'D')
  BEGIN
  ALTER TABLE [dbo].[ELMAH_Error] ADD  CONSTRAINT [DF_ELMAH_Error_ErrorId]  DEFAULT (newid()) FOR [ErrorId]
  END
  
  GO
  SET ANSI_NULLS ON
  SET QUOTED_IDENTIFIER ON
  IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ELMAH_GetErrorsXml]') AND type in (N'P', N'PC'))
  BEGIN
  EXEC dbo.sp_executesql @statement = N'
  CREATE PROCEDURE [dbo].[ELMAH_GetErrorsXml]
  (
      @Application NVARCHAR(60),
      @PageIndex INT = 0,
      @PageSize INT = 15,
      @TotalCount INT OUTPUT
  )
  AS 
  
      SET NOCOUNT ON
  
      DECLARE @FirstTimeUTC DATETIME
      DECLARE @FirstSequence INT
      DECLARE @StartRow INT
      DECLARE @StartRowIndex INT
  
      SELECT 
          @TotalCount = COUNT(1) 
      FROM 
          [ELMAH_Error]
      WHERE 
          [Application] = @Application
  
      -- Get the ID of the first error for the requested page
  
      SET @StartRowIndex = @PageIndex * @PageSize + 1
  
      IF @StartRowIndex <= @TotalCount
      BEGIN
  
          SET ROWCOUNT @StartRowIndex
  
          SELECT  
              @FirstTimeUTC = [TimeUtc],
              @FirstSequence = [Sequence]
          FROM 
              [ELMAH_Error]
          WHERE   
              [Application] = @Application
          ORDER BY 
              [TimeUtc] DESC, 
              [Sequence] DESC
  
      END
      ELSE
      BEGIN
  
          SET @PageSize = 0
  
      END
  
      -- Now set the row count to the requested page size and get
      -- all records below it for the pertaining application.
  
      SET ROWCOUNT @PageSize
  
      SELECT 
          errorId     = [ErrorId], 
          application = [Application],
          host        = [Host], 
          type        = [Type],
          source      = [Source],
          message     = [Message],
          [user]      = [User],
          statusCode  = [StatusCode], 
          time        = CONVERT(VARCHAR(50), [TimeUtc], 126) + ''Z''
      FROM 
          [ELMAH_Error] error
      WHERE
          [Application] = @Application
      AND
          [TimeUtc] <= @FirstTimeUTC
      AND 
          [Sequence] <= @FirstSequence
      ORDER BY
          [TimeUtc] DESC, 
          [Sequence] DESC
      FOR
          XML AUTO
  
  ' 
  END
  GO
  SET ANSI_NULLS ON
  SET QUOTED_IDENTIFIER ON
  IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ELMAH_GetErrorXml]') AND type in (N'P', N'PC'))
  BEGIN
  EXEC dbo.sp_executesql @statement = N'
  CREATE PROCEDURE [dbo].[ELMAH_GetErrorXml]
  (
      @Application NVARCHAR(60),
      @ErrorId UNIQUEIDENTIFIER
  )
  AS
  
      SET NOCOUNT ON
  
      SELECT 
          [AllXml]
      FROM 
          [ELMAH_Error]
      WHERE
          [ErrorId] = @ErrorId
      AND
          [Application] = @Application
  
  ' 
  END
  GO
  SET ANSI_NULLS ON
  SET QUOTED_IDENTIFIER ON
  IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ELMAH_LogError]') AND type in (N'P', N'PC'))
  BEGIN
  EXEC dbo.sp_executesql @statement = N'
  CREATE PROCEDURE [dbo].[ELMAH_LogError]
  (
      @ErrorId UNIQUEIDENTIFIER,
      @Application NVARCHAR(60),
      @Host NVARCHAR(30),
      @Type NVARCHAR(100),
      @Source NVARCHAR(60),
      @Message NVARCHAR(500),
      @User NVARCHAR(50),
      @AllXml NVARCHAR(MAX),
      @StatusCode INT,
      @TimeUtc DATETIME
  )
  AS
  
      SET NOCOUNT ON
  
      INSERT
      INTO
          [ELMAH_Error]
          (
              [ErrorId],
              [Application],
              [Host],
              [Type],
              [Source],
              [Message],
              [User],
              [AllXml],
              [StatusCode],
              [TimeUtc]
          )
      VALUES
          (
              @ErrorId,
              @Application,
              @Host,
              @Type,
              @Source,
              @Message,
              @User,
              @AllXml,
              @StatusCode,
              @TimeUtc
          )
  
  ' 
  END
  GO
  

• To test it, go to http://yoursite/elmah.axd

Keywords: Windows Azure Exception Handling Logging