Explorations in software troubleshooting
A system is a point of view – natural for a poet, yet terrifying for a scientist. Gerald Weinberg, An Introduction to General Systems Thinking, page 52. Up until this point, I haven’t really addressed the idea of “a system” directly, but systems are implicit in all of these discussions. A “system” is the thing …
I was running a performance test recently, and I saw some odd behavior. My usual process is to restart the application, let it finish initializing, and then run a simulation for about an hour. That’s usually enough time to collect enough samples to get a good idea of the performance of various requests. My 1 …
Recently, I’ve been writing about hypothesis generators – techniques you can use to generate problem-solving ideas if you get stuck. The next hypothesis generator is the principle of recent change. You can use this one if you are looking at system that worked at one time, but is not working now. The principle of recent …
In my last article, I introduced the first of the hypothesis generators – techniques you can use to generate problem-solving ideas if you get stuck. The next hypothesis generator to consider is “Make it look like this”. You can use this one if you have two separate deployments of the same software system where one …
The scientific method gives you a powerful framework for organizing your troublehacking activities. When applying the scientific method, you formulate hypotheses and then your work focuses on proving or disproving the hypotheses. But just how do you go about formulating a hypothesis? Sometimes all it takes is a few minutes of brainstorming, but what do …
Introduction Sometimes, a performance problem appears rather suddenly. One day, performance is reasonable but the next, operations are much slower. This can sometimes be caused by a change in behavior in the database layer. Oracle, for example, may change execution plans for SQL statements after updating statistics. In this article, I’ll look at why that …
In theory, there is no difference between theory and practice. But, in practice, there is. Jan L. A. van de Snepscheut as quoted by Doug Rosenberg and Matt Stephens (2007) Use Case Driven Object Modeling with UMLTheory and Practice p. xxvii Most of the TROUBLEhacker site discusses the theory of troubleshooting. There is material on …
I was recently reminded about the difficulty in seeing what’s there by my coffee machine. My mental model of the coffee machine is pretty simple: I put in the grounds, I add water, and I press a button to make coffee. My machine has some other features and some other buttons, but I don’t care …
Do not fall into the error of the artisan who boasts of twenty years experience in his craft while in fact he has had only one year of experience — twenty times. Trevanian in Shubumi: A Novel. I genuinely enjoy problem solving. But there is one thing I hate: solving a problem more than once. …
If you have any degree of success as a trouble hacker, you’ll soon get the chance to tackle harder and harder problems. Sooner or later, you are going to run into something that you haven’t seen before. You’ll be in an unfamiliar area of code, or you’ll be looking at technology you haven’t yet worked …