Tune logging levels in Production without recompiling code

IAP Software Development Practice JournalThis article first appeared in Software Development Practice, Issue 1, published by IAP (ISSN 2050-1455) 

Abstract

When raising log events in code it can be difficult to choose a severity level (such as Error, Warning, etc.) which will be appropriate for Production; moreover, the severity of an event type may need to be changed after the application has been deployed based on experience of running the application. Different environments (Development (Dev), User Acceptance Testing (UAT), Non-Functional Testing (NFT), Production, etc.) may also require different severity levels for testing purposes. We do not want to recompile an application just to change log severity levels; therefore, the severity level of all events should be configurable for each application or component, and be decoupled from event-raising code, allowing us to tune the severity without recompiling the code.

A simple way to achieve this power and flexibility is to define a set of known event IDs by using a sparse enumeration (enum in C#, Java, and C++), combined with event-ID-to-severity mappings contained in application configuration, allowing the event to be logged with the appropriate configured severity, and for the severity to be changed easily after deployment.

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Using LogParser and Log Replay to Bootstrap Load Test Scripts

In a previous post I mentioned how Microsoft LogParser can be used to discover HTTP endpoints in legacy applications. Another great use for LogParser is to generate files to drive load test scripts.

Loaded truck by jcurtis4082 (Flickr)

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Endpoint Discovery using Microsoft LogParser

A few years ago, I was working on a project for a UK client who needed to replace or rewrite a legacy inventory management  web application written in classic ASP. The problem: no documentation, and complicated, spaghetti source code with many apparently duplicate or redundant ASP files and ASMX web service endpoints.

Finger pointing by bhollar (Flickr)

Which ASP pages were actually in use? We had to find a way to limit our application migration efforts to  only those pages which were used by the application. A colleague at the time introduced me to what must be one of the best-kept secrets in the Windows developer world: Microsoft Log Parser.

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Microsoft Application Blocks

Microsoft Application Blocks form a collection of ready-built ‘clumps’ of code which solve common problems such as security management, data access, logging, etc. They are the tangible result of the Microsoft Patterns and Practices advice: all of it sound and solid.

John Jakovich, one of the 4 Guys From Rolla, gives a useful An Introduction and Overview of the Microsoft Application Blocks. He summarises the utility of the Application Blocks thus:

…you don’t have to worry about the tedious details required to return a DataReader or write an exception to the System Log. This allows us to concentrate on the business logic in our applications.

I have written too many logging frameworks in the past: it’s boring above all else. I just want to log exceptions in a thread-safe manner, with a unique ID.which I can display to the user if necessary. If someone (i.e MS) has already written code to do (most of) this, then fine – I’ll use it.

The Security block is particularly useful for ASP.NET 1.1, where security and profile management is not as simple as in version 2.0. All that boring stuff about storing Role information in cookies? Solved! Better still, any security holes will be fixed by MS. Again, more time to concentraste on business logic.

Design Guidelines for Class Library Developers

The Application Blocks tie in nicely with a set of guidelines from MS on class library development. They include advice on:

  • array usage
  • exposure to COM
  • casting
  • threading

and several other subjects. This is basically just a gloop of Common Sense, but well worth a read.

MBR BootFX Application Framework

An alternative to the MS Application Blocks comes from Matt Baxter-Reynolds (he of DotNet247) in the form of BootFX:

The MBR BootFX Application Framework is a best-of-breed application
framework that we offer to all our clients who engage us to develop
software applications or software components for them. It’s designed
to give us a “leg up” on new projects by providing a tried and tested
code base for common software development activities.

There are lots of goodies there, including Object Relational Mapping (ORM), and support for SQL Server, Oracle, and MySQL databases. To top it all, it’s open source, via the Mozilla Public Licence 1.1. I met Matt 18 months or so back at a seminar run by Iridium; very personable guy.

Tracking Exceptions in Web Services with GUIDs

Note: This article first appeared in CVu Issue 17.5 (October 2005). CVu is the journal of ACCU, an organisation in the UK dedicated to excellence in software programming. Some links may not work.

Synopsis

This article demonstrates a technique for tracking exceptions across process boundaries in distributed systems using Globally Unique Identifiers (GUIDs); data from log files, bug reports, and on-screen error messages can then be correlated, allowing specific errors to be pinpointed.

Particular attention is paid to XML Web Services, with additional reference to DCOM, CORBA, Java/RMI and .Net Remoting.

The examples are given in C# [.NET 1.1], but the technique can be applied easily to Java and other languages.

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