basquang™ on clouds

August 25, 2011

Logging: Using Elmah, Nuget in ASP.NET MVC 3 and Oracle database

Filed under: Logging,MVC,Oracle — basquang @ 3:00 PM

Logging is one of the most important thing you must to thinking about when intend to building a production website. There are many many way to implement logging in a website, and it was not able to easily.

So in this article, I will simplify the way to implement logging in ASP.NET MVC 3 using Elmah!

Configure Elmah with NuGet

1. Create a ASP.NET MVC 3 Internet Application

imageimage

2. From Visual Studio select Tools –> Library Package Manager –> Manage NuGet Packages…

In Manage NuGet Packages…Windows, seach Elmah then install this package for your project as bellow when finished.

imageimage

3. NuGet will automatically add reference elmah.dll to your project and the appropriate element of elmah on web.config file.

Now you can ready to test the Elmah logging by navigate your website to http://[yourwebsite]/elmah.axd as bellow

image

Logging your exception with Elmah.

But because we would like to use Elmah to handle our exceptions instead of MVC, we will replace the standard MVC [HandleError] attribute with our own custom attribute called [HandleErrorWithElmah].

So you must to create those class bellow

a. the HandleErrorWithELMAHAttribute.cs class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Elmah;

namespace MvcApplicationElmah.Logging
{
    public class HandleErrorWithELMAHAttribute : HandleErrorAttribute
    {
        public override void OnException(ExceptionContext context)
        {
            base.OnException(context);

            var e = context.Exception;
            if (!context.ExceptionHandled   // if unhandled, will be logged anyhow
                    || RaiseErrorSignal(e)      // prefer signaling, if possible
                    || IsFiltered(context))     // filtered?
                return;

            LogException(e);
        }

        private static bool RaiseErrorSignal(Exception e)
        {
            var context = HttpContext.Current;
            if (context == null)
                return false;
            var signal = ErrorSignal.FromContext(context);
            if (signal == null)
                return false;
            signal.Raise(e, context);
            return true;
        }

        private static bool IsFiltered(ExceptionContext context)
        {
            var config = context.HttpContext.GetSection("elmah/errorFilter")
                                     as ErrorFilterConfiguration;

            if (config == null)
                return false;

            var testContext = new ErrorFilterModule.AssertionHelperContext(
                                                                context.Exception, HttpContext.Current);

            return config.Assertion.Test(testContext);
        }

        private static void LogException(Exception e)
        {
            var context = HttpContext.Current;
            ErrorLog.GetDefault(context).Log(new Error(e, context));
        }
    }
}

b. The ErrorHandlingControllerFactory.cs class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;

namespace MvcApplicationElmah.Logging
{
    public class ErrorHandlingControllerFactory : DefaultControllerFactory
    {
        /// <summary>
        /// Injects a custom attribute 
        /// on every action that is invoked by the controller
        /// </summary>
        /// <param name="requestContext">The request context</param>
        /// <param name="controllerName">The name of the controller</param>
        /// <returns>An instance of a controller</returns>
        public override IController CreateController(
            RequestContext requestContext,
            string controllerName)
        {
            var controller =
                base.CreateController(requestContext,
                controllerName);

            var c = controller as Controller;

            if (c != null)
            {
                c.ActionInvoker =
                    new ErrorHandlingActionInvoker(
                        new HandleErrorWithELMAHAttribute());
            }

            return controller;
        }
    }
}

c. The ErrorHandlingActionInvoker.cs class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace MvcApplicationElmah.Logging
{
    public class ErrorHandlingActionInvoker : ControllerActionInvoker
    {
        private readonly IExceptionFilter filter;

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="filter">The exception filter to inject</param>
        public ErrorHandlingActionInvoker(IExceptionFilter filter)
        {
            if (filter == null)
            {
                throw new ArgumentNullException("filter");
            }

            this.filter = filter;
        }

        /// <summary>
        /// This methods returns all of the normal filters used
        /// PLUS it appends our custom filter to the end of the list 
        /// </summary>
        /// <param name="controllerContext">The context of the controller</param>
        /// <param name="actionDescriptor">The action descriptor</param>
        /// <returns>All of the action filters</returns>
        protected override FilterInfo GetFilters(
            ControllerContext controllerContext,
            ActionDescriptor actionDescriptor)
        {
            var filterInfo =
                base.GetFilters(controllerContext,
                actionDescriptor);

            filterInfo.ExceptionFilters.Add(this.filter);

            return filterInfo;
        }
    }
}

Now throw a new Exception in About action on your HomeController

public ActionResult About()
        {
            throw new Exception("A test exception for ELMAH");
            return View();
        }

Enable custom error in web.config

<customErrors mode="On" defaultRedirect="/Home/Error"></customErrors>

Register your custom error handler on Global.asax

protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            RegisterGlobalFilters(GlobalFilters.Filters);
            RegisterRoutes(RouteTable.Routes);

            ControllerBuilder.Current.SetControllerFactory(new MvcApplicationElmah.Logging.ErrorHandlingControllerFactory());
        }

Now, It’s time to test your custom exception that logged in Elmah.

imageimage

Logging to Oracle database

With a big website we need to log all exception to database. Elmah supports both of SQL Server and Oracle and more kind of databases. Is this section I will describe how to log the errors in Oracle database.

Firstly, we need to run the Oracle.sql script that provided from Elmah package that you has already downloaded.

image

/*
  
   ELMAH - Error Logging Modules and Handlers for ASP.NET
   Copyright (c) 2004-9 Atif Aziz. All rights reserved.
  
    Author(s):
  
      James Driscoll, mailto:jamesdriscoll@btinternet.com
  
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
  
*/

-- $Id: Oracle.sql 568 2009-05-11 14:18:34Z azizatif $

-- NB This script assumes you have logged on in the schema where you want to create the ELMAH objects

-- create a sequence for the errors (user to simulate an identity in SQL Server)
CREATE SEQUENCE elmah$error_seq START WITH 1 INCREMENT BY 1 NOMAXVALUE NOCYCLE NOCACHE NOORDER;

-- create the table to store the data
-- you can optionally specify tablespaces here too!
CREATE TABLE elmah$error
(
    -- if using Oracle 10g and above you can add DEFAULT SYS_GUID() 
    -- to the errorid definition.
    -- Oracle 8i doesn't like it with an NVARCHAR2
    -- haven't tested it against 9i
    errorid         NVARCHAR2(32) NOT NULL,
    application     NVARCHAR2(60) NOT NULL,
    host            NVARCHAR2(30) NOT NULL,
    type            NVARCHAR2(100) NOT NULL,
    source          NVARCHAR2(60),
    message         NVARCHAR2(500) NOT NULL,
    username        NVARCHAR2(50),
    statuscode      NUMBER NOT NULL,
    timeutc         DATE NOT NULL,
    sequencenumber  NUMBER NOT NULL,
    allxml          NCLOB NOT NULL,
    CONSTRAINT idx_elmah$error_pk 
        PRIMARY KEY (errorid) 
        USING INDEX -- TABLESPACE "TABLESPACE FOR INDEX"
) -- TABLESPACE "TABLESPACE FOR DATA"
/

-- trigger to make sure we get our sequence number in the table
CREATE TRIGGER trg_elmah$error_bi
BEFORE INSERT ON elmah$error
FOR EACH ROW
BEGIN
    SELECT elmah$error_seq.NEXTVAL INTO :new.sequencenumber FROM dual;
END trg_elmah$error_bi;
/

-- create the index on the table
CREATE INDEX idx_elmah$error_app_time_seq ON elmah$error(application, timeutc DESC, sequencenumber DESC)
/

-- package containing the procedure we need for ELMAH to log errors
CREATE OR REPLACE PACKAGE pkg_elmah$log_error
IS
    PROCEDURE LogError
    (
        v_ErrorId IN elmah$error.errorid%TYPE,
        v_Application IN elmah$error.application%TYPE,
        v_Host IN elmah$error.host%TYPE,
        v_Type IN elmah$error.type%TYPE,
        v_Source IN elmah$error.source%TYPE,
        v_Message IN elmah$error.message%TYPE,
        v_User IN elmah$error.username%TYPE,
        v_AllXml IN elmah$error.allxml%TYPE,
        v_StatusCode IN elmah$error.statuscode%TYPE,
        v_TimeUtc IN elmah$error.timeutc%TYPE
    );

END pkg_elmah$log_error;
/

CREATE OR REPLACE PACKAGE BODY pkg_elmah$log_error
IS
    PROCEDURE LogError
    (
        v_ErrorId IN elmah$error.errorid%TYPE,
        v_Application IN elmah$error.application%TYPE,
        v_Host IN elmah$error.host%TYPE,
        v_Type IN elmah$error.type%TYPE,
        v_Source IN elmah$error.source%TYPE,
        v_Message IN elmah$error.message%TYPE,
        v_User IN elmah$error.username%TYPE,
        v_AllXml IN elmah$error.allxml%TYPE,
        v_StatusCode IN elmah$error.statuscode%TYPE,
        v_TimeUtc IN elmah$error.timeutc%TYPE
    )
    IS
    BEGIN
        INSERT INTO elmah$error
            (
                errorid,
                application,
                host,
                type,
                source,
                message,
                username,
                allxml,
                statuscode,
                timeutc
            )
        VALUES
            (
                UPPER(v_ErrorId),
                v_Application,
                v_Host,
                v_Type,
                v_Source,
                v_Message,
                v_User,
                v_AllXml,
                v_StatusCode,
                v_TimeUtc
            );

    END LogError;   

END pkg_elmah$log_error;
/


-- package containing the procedure we need for ELMAH to retrieve errors
CREATE OR REPLACE PACKAGE pkg_elmah$get_error
IS
	-- NB this is for backwards compatibility with Oracle 8i
    TYPE t_cursor IS REF CURSOR;
    
    PROCEDURE GetErrorXml
    (
        v_Application IN elmah$error.application%TYPE,
        v_ErrorId IN elmah$error.errorid%TYPE,
        v_AllXml OUT elmah$error.allxml%TYPE
    );

    PROCEDURE GetErrorsXml
    (
        v_Application IN elmah$error.application%TYPE,
        v_PageIndex IN NUMBER DEFAULT 0,
        v_PageSize IN NUMBER DEFAULT 15,
        v_TotalCount OUT NUMBER,
        v_Results OUT t_cursor
    );
    
END pkg_elmah$get_error;
/

CREATE OR REPLACE PACKAGE BODY pkg_elmah$get_error
IS
    PROCEDURE GetErrorXml
    (
        v_Application IN elmah$error.application%TYPE,
        v_ErrorId IN elmah$error.errorid%TYPE,
        v_AllXml OUT elmah$error.allxml%TYPE
    )
    IS
    BEGIN
        SELECT  allxml
        INTO    v_AllXml
        FROM    elmah$error
        WHERE   errorid = UPPER(v_ErrorId)
        AND     application = v_Application;
    EXCEPTION
        WHEN NO_DATA_FOUND THEN
            v_AllXml := NULL;
    END GetErrorXml;

    PROCEDURE GetErrorsXml
    (
        v_Application IN elmah$error.application%TYPE,
        v_PageIndex IN NUMBER DEFAULT 0,
        v_PageSize IN NUMBER DEFAULT 15,
        v_TotalCount OUT NUMBER,
        v_Results OUT t_cursor
    )
    IS
        l_StartRowIndex NUMBER;
        l_EndRowIndex   NUMBER;
    BEGIN
        -- Get the ID of the first error for the requested page
        l_StartRowIndex := v_PageIndex * v_PageSize + 1;
        l_EndRowIndex := l_StartRowIndex + v_PageSize - 1;
        
        -- find out how many rows we've got in total
        SELECT  COUNT(*)
        INTO    v_TotalCount
        FROM    elmah$error
        WHERE   application = v_Application;

        OPEN v_Results FOR
            SELECT  *
            FROM
            (
                SELECT  e.*,
                        ROWNUM row_number
                FROM
                (
                    SELECT  /*+ INDEX(elmah$error, idx_elmah$error_app_time_seq) */
                            errorid,
                            application,
                            host,
                            type,
                            source,
                            message,
                            username,
                            statuscode,
                            timeutc
                    FROM    elmah$error
                    WHERE   application = v_Application
                    ORDER BY
                            timeutc DESC, 
                            sequencenumber DESC
                ) e
                WHERE ROWNUM <= l_EndRowIndex
            )
            WHERE   row_number >= l_StartRowIndex;
            
    END GetErrorsXml;

END pkg_elmah$get_error;
/

/* 
-- If you are securing the packages above, you will need to grant execute
-- privileges on them so that they can be called by the user connecting to the database.
-- NB As long as you use the schema owner for the connection string, this is not necessary,
-- although this is generally discouraged by Best Practices.

-- Option 1) Allow any user to execute the package (not recommended)
-- replace OWNER for the schema owner in the following statement
GRANT EXECUTE ON OWNER.pkg_elmah$log_error TO PUBLIC;
GRANT EXECUTE ON OWNER.pkg_elmah$get_error TO PUBLIC;

-- Option 2) Allow a single user to execute the package (better)
-- replace OWNER for the schema owner in the following statement
GRANT EXECUTE ON OWNER.pkg_elmah$log_error TO USER_NAME;
GRANT EXECUTE ON OWNER.pkg_elmah$get_error TO USER_NAME;

-- Option 3) Lock things down so that one user can only log errors, while another user can read and log errors (most secure)
-- replace OWNER for the schema owner in the following statement
-- LOGGING_USER_NAME will be used to connect to the database in all sites which log errors to the database
GRANT EXECUTE ON OWNER.pkg_elmah$log_error TO LOGGING_USER_NAME;
-- ADMIN_USER_NAME will be used to connect to the database in an admin portal which allows users to read errors
GRANT EXECUTE ON OWNER.pkg_elmah$log_error TO ADMIN_USER_NAME;
GRANT EXECUTE ON OWNER.pkg_elmah$get_error TO ADMIN_USER_NAME;

-- NB if you do take this approach, be sure to set the schemaOwner parameter in your web.config
*/

Then you need to install “Elmah on Oracle” package from NuGet. It will automatically add appropriate elements in web.config to support logging to Oracle database

image

Finally, you have to manual change the connection string to your oracle database that store the Elmah Logging table as bellow

<add name="elmah-oracle" connectionString="Data Source=XE;User ID=loggingdb;Password=*****;" />

You could be able to  test your configuration now. Starting the website, click on About then looking for a new record has already added to ELMAH$ERROR table in Oracle database.

image

Hope this help!

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