elmah

Diagnosing a collation issue in a MySql stored procedure

Sebastian Solnica7 Comments

We are using Elmah on production to log problems in our web applications. Elmah logs are stored in a MySql table which structure is a slightly modified version of the elman_error table from the original Elmah script (I changed the engine to InnoDB and added partitioning over TimeUTC column):

CREATE TABLE IF NOT EXISTS `elmah_error` (
  `ErrorId` CHAR(36) NOT NULL ,
  `Application` VARCHAR(60) NOT NULL ,
  `Host` VARCHAR(50) NOT NULL ,
  `Type` VARCHAR(100) NOT NULL ,
  `Source` VARCHAR(60) NOT NULL ,
  `Message` VARCHAR(500) NOT NULL ,
  `User` VARCHAR(50) NOT NULL ,
  `StatusCode` INT(10) NOT NULL ,
  `TimeUtc` DATETIME NOT NULL ,
  `Sequence` INT(10) NOT NULL AUTO_INCREMENT ,
  `AllXml` TEXT NOT NULL ,
  PRIMARY KEY (`Sequence`, `TimeUtc`) ,
  INDEX `IX_ErrorId` (`ErrorId`(8) ASC) , -- UNIQUE can't be created if it does not include all partition columns
  INDEX `IX_ELMAH_Error_App_Time_Seql` (`Application`(10) ASC, `TimeUtc` DESC, `Sequence` DESC) ,
  INDEX `IX_ErrorId_App` (`ErrorId`(8) ASC, `Application`(10) ASC) )
ENGINE InnoDB DEFAULT CHARACTER SET latin2
partition by range columns(`TimeUtc`)
(
  partition before20130719 values less than ('2013-07-19 00:00')
);

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Making elmah.axd a log viewer for multiple applications

Sebastian Solnica6 Comments

Elmah is a great exception logger for web applications. Next to the exception data (stacktrace, exception message etc.) it collects detailed request and runtime information. If I also mention that it’s easy to install and highly configurable it comes with no surprise that it became an industrial logging standard for .NET web applications. Elmah gives you a great choice of places where you can send your logs, though a database is the one I consider most useful. What I also value in Elmah is its log viewer (elmah.axd) – it has a nice exception list and a great exception details screen – I wish the ASP.NET Yellow Screen of Death had that look :). The only thing I don’t really like in this viewer is a fact that by default it is bound to the application that has Elmah installed and is accessible only under http://<app-url>/elmah.axd. If you do not secure access to this handler everyone can see detailed information on your code and environment – just have a look how many developers forget about it. In this post I will show you how to remove the elmah.axd handler from your application and how to create a separate ASP.NET application that would be a central Elmah log viewer for your applications.

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