Everything I can find about Software Maintenance

Given that most of us will spend most of our careers maintaining and supporting software and not building something new from scratch, there is a surprising and disappointing lack of useful information on software maintenance, on the problems that we all face in software maintenance. I’ve tried to put together here an index to useful books, articles and blog posts and white papers on software maintenance.

Last updated: 2011-July-12

Maintenance Blog Posts

Jeff Atwood’s The Noble Art of Maintenance Programming is a thoughtful post on how maintenance programmers are unjustifiably unappreciated: how maintenance is much harder and more important than most people, even the people doing the work, understand.

In Sustained engineering Idiocy, Microsoft’s Eric Brechner explores how to organize your maintenance team, and the pros and cons of juggling maintenance and support responsibilities with new development work. Although some of his writing is internally Microsoft-focused, his blog is worth following for general good ideas on software development management and maintenance.

Robert Glass wrote an insightful essay on the challenges in software maintenance, "Software Maintenance is a Solution, not a Problem", in his book Software Conflict 2.0: The Art and Science of Software Engineering. You can read a copy of the essay here.

Greg Jorgensen, the Typical Programmer, shares a positive perspective on The Joys of Maintenance Programming, describing how maintenance programming can be a satisfying and successful career choice.

Steve Shaw at Intelliware wrote a short paper on his team's experience following Agile methods in software maintenance; what practices worked (short iterations, testing, prioritization, common code ownership) and what didn't (pairing, stories and story cards, stand-ups, metaphor).

The Good Books

There are some excellent books and other resources on writing and maintaining code. Starting with Code Complete 2 by Steve McConnell. The definitive book on how to write good code, maintain it and debug it.

Legacy code means different things to different people. For some programmers, legacy code is code is any code that they didn’t write. For others, it is code that stills runs on abandoned or out-of-date platforms and technologies. But everyone agrees that it is code that is difficult to understand, difficult to support and difficult to change. And in maintenance you are going to spend a lot of time dealing with it. Working Effectively with Legacy Code by Michael Feathers lays out how to get a legacy code base under control, and the steps on how to make changes safely and properly.

The Passionate Programmer by Chad Fowler offers some good advice to programmers (and managers) looking for meaning in software development and maintenance.

More on Legacy Code

There are also a couple of good online presentations from the smart people at ThoughtWorks on how they have dealt with legacy code problems. One presentation by Matt Simons and Jonny LeRoy covers how to get a handle on existing code, mapping the code and identifying risk areas, creating dashboards to visualize the state of the code base using open source tools like Panopticode and Codecity (which offers a cool 3D cityscape view of your code, making metrics fun for everyone), or Sonar (actually, they didn’t mention Sonar, but it’s another good source management dashboard). Then they outline different strategies for incrementally re-writing large applications, emphasizing Martin Fowler’s Strangler pattern, and how they have applied these ideas to different customer problems.

Another good presentation from Josh Graham at ThoughtWorks on Brownfield Software walks through an interesting case study where his team came in to help with a major overhaul of a large, 10-year-old core business system.

Refactoring is a foundational discipline for maintenance – Martin Fowler put a name and a disciplined structure to the work that we all do, or should do, when changing code. Seriously, is there anybody who hasn’t read this book by now, who doesn’t follow some/most of these ideas in maintaining code?

Debug It! by Paul Butcher is a narrowly-focused but useful book, about debugging, problem-solving techniques, handling bugs, and writing code that is easy to debug. Especially useful for programmers new to maintenance.

Managing Maintenance

There are some great books on managing software development projects, like Steve McConnell's Rapid Development, and Scott Berkun's Making Things Happen. Many of the ideas in these books will help you in managing software maintenance work.

There are only a couple of books that take on managing software maintenance:

Alain April and some other researchers have put together a Software Maintenance Maturity Model, a la the CMMI. It's obviously process-heavy and bureaucratic, but it does a thorough job of mapping out all of the work involved in software maintenance, and it's interesting in an abstract way.

If you're managing a large enterprise maintenance team and working through a lot of structure and standards, then Thomas Pigoski's Practical Software Maintenance offers advice based on real experience - the author ran a large maintenance organization for the US Navy, and is now the CEO of TechSoft, an outsourcing firm that handles maintenance for other companies. Unfortunately this book is out of date (published 1996) and predates modern Agile and Lean methods and practices and new technologies. Pigoski also wrote the chapter on software maintenance in the IEEE SWEBOK, an academic definition of software engineering.

Another academic book which I can't recommend for practitioners is Software Maintenance: Concepts and Practice by Penny Grubb and Armstrong Takang. If you're already working in maintenance, you won't find anything here that you don't already know or that will change the way that you think or work. It's more of an introductory text for undergrad Comp Sci courses.

Studies, Statistics and Lies

Dr. Jussi Koskinen, a Comp Sci professor in Finland, maintains a useful summary of software maintenance cost data and sources.

If I want any kind of data on software development or software maintenance, the first person that I go to is Capers Jones. His book on Estimating Software Costs was last updated in 2007, and includes extensive data on software cost information and statistics and trends on software maintenance and support. Or you can read Applied Software Measurement or Software Engineering Best Practices - all of these books are built on the same comprehensive research. You can spend days going through this stuff - I have, and I keep finding interesting things.

Some of his research specific to software maintenance and legacy software is captured in a white paper called Geriatric Issues of Aging Software. A couple of different versions of this paper can be found on the web, the best of them is found in CrossTalk: The Journal of Defense Software Engineering dated December 2007.

One of the foundational studies on software maintenance is more than 30 years old now: a study of software maintenance at 487 IT organizations by Lientz and Swanson. It's widely referenced, and still the most comprehensive analysis of what work goes into maintenance (or at least what did in 1978). A newer (1998), smaller, but still interesting study by Janice Singer talks a lot about bugs and bug tracking, and how unimportant documentation actually is in maintenance.

Building, releasing and deploying code

And there are some good books on building, deploying and delivering code, on Continuous Integration and source code management, all of which are important in maintaining and releasing code. The best of these is the new book on Continuous Delivery by Jez Humble and David Farley. It’s full of practical advice on how to improve your code build and deployment practices; and on data migration and test automation strategies; and more far-out ideas on how far-out you can push automation in build and deployment.

Lean and Kanban and Maintenance

If you are interested in how Lean Manufacturing and Kanban ideas can be applied to software maintenance, and quite a few people are, a place to start is the XIT case study which explains how Kanban was first used to speed up and simplify management of maintenance work by a small cross-application team at Microsoft. I think there’s too much hype and religious debate around what is a conceptually simple idea (visualizing and limiting work in progress), but Kanban offers a natural framework for getting control over maintenance and support work, helping to deal with interruptions and constantly changing priorities.

Operations and DevOps

Developers need to understand how their code runs in production, need to care about and know about operations and performance and how to handle failures. This becomes even more important, more necessary, in maintenance: it’s a reality that maintenance teams face all day each day, rather than just another set of requirements for the future. Some smart people in the DevOps community are trying to come up with a more collaborative and agile way for operations and development teams to work together. Most of their work focuses on large-scale Web Operations problems and operations toolchains, but there is some good thinking here on how to improve deployment, on metrics and monitoring, and on dealing with architectural problems like scaling, and failure handling and recovery.

While helpful, most of the thinking in DevOps is being done from the operations point of view (maybe it should be called OpsDev instead…). The best book on operations problems by and for developers and software architects is still Release It! by Michael Nygard. He makes clear how important it is to, and how to, design scalable and resilient software architectures, and how and why to build an operations view into your system.

If you are working with Ops (especially in an enterprise shop) you should understand the basics of ITIL, and the cost and risks of change in production, and how to to get a production system under control. The best place to start on this is The Visible Ops Handbook, a tiny primer on intelligent IT change management.

Dealing with Data

One of the biggest problems in software maintenance is handling changes to data and data models. Scott Ambler's book Refactoring Databases walks through an incremental approach to making structural changes to database models, and how to test and deploy these changes.

Secure Software Maintenance

Dealing with security risks for legacy systems is another wormcan, and you're not going to find a lot of information to help you understand where to start, other than this set of white papers on legacy systems and COTS from Cigital, available on the US Department of Homeland Security’s Build Security In portal.

Forums and Discussion Groups

I can't find any discussion groups on software maintenance or sustaining engineering.

Stack Overflow has some interesting threads on maintenance and refactoring and other maintenance problems. It’s one of the mainstay resources for developers looking for advice on maintenance issues or anything else for that matter.

And finally...

You can learn a lot from antipatterns. How to Write Unmaintainable Code by Roedy Green is thorough, thought-provoking and fun.

I would like to hear from people about any other useful books, blogs, articles or forums that focus on software maintenance and support problems - what resources you trust, what you have found helpful.