Diagnostics Anonymous

Photo of Curtis Lusmore Curtis Lusmore,

When working with large systems, especially with software, inevitably something will go wrong and you’ll be stuck trying to diagnose it. My years of developing software have given me a lot of practice diagnosing errors or unintended behaviour in software systems (usually in my own code), and over time I’ve built up a systematic process that I run through to speed up the process. In writing this post, I came to realise that my process actually has quite a lot in common with 12-step programs, so I’ve tweaked the format a little to make the content a little more interesting.

1. We admitted that there was a problem—that the system had become unmanageable

The first step is to admit that you have a problem. Sometimes you are working on something and struggling to get it to behave how you want, and you are just reaching the point where you begin to question whether you are taking the right approach. Or perhaps you saw what you thought was an isolated incident that you corrected, but you’re starting to suspect there might be more to it. It’s important to stop and admit that there is a problem if you want to have any hope of understanding it.

Hopefully when you started doing whatever went wrong, you had an idea in your head of what you were hoping to achieve. If you didn’t, hey, maybe you don’t need to solve the problem after all. Just leave everything broken and move on. More likely, you were trying to solve a particular problem or achieve a particular outcome. Keep this in the back of your mind because it’s important that you remind yourself of it every so often to make sure you’re on track to actually solving it, that you haven’t gone so far down a rabbit hole that you forget what you were trying to do in the first place.

Quite often, when attempting to solve one problem you stumble upon a second problem, and the best solution is to not solve the second problem at all, but to find a better solution to the first problem. This scenario is known as an XY problemwhere you encounter a problem X, attempt to solve it but encounter problem Y, and then focus on Y. As an example, if you’re stuck trying to figure out how to get cheese to stick to the side of the bread when you put it into the toaster, perhaps you need to realise that the real problem is you want to make grilled cheese and the real solution is to use a sandwich toaster, not a regular toaster.

2. Came to believe there must be a way to resolve it

Now that you have admitted that you have a problem, the next step is to understand how things could be better. Ask yourself the following questions. “What do I think should happen? What are the outputs I’m hoping to see?” How will you know when you’ve solved the problem? If you had a magic lamp, what wish would you ask of the genie? Genies can be really pedantic so you need to be as precise and unambiguous as possible.

3. Made a decision to turn our will over to resolving it

Unfortunately you probably don’t have a magic lamp, so you’re going to have to resolve the problem yourself. It’s important to commit yourself to solving the problem, adjust your mindset, and make sure you have the best environment for tackling it. Try to clear any clutter off your desk and your screen, pull up any documents that might be useful, and get a pen and paper ready.

4. Made a searching and fearless inventory of the system and environment

Gather up any relevant information you can find. Current log files, old log files, error messages, network traces, known issue lists, documentation, requirements, test cases, configuration, patch information, everything. Information is key here and you want as much of it as you can. If you can find historical data, get it because it can help you track changes over time.

5. Stated to ourselves the exact nature of the problem

It’s important to take note of what behaviour you’re actually seeing and how to compare it with what you want to happen. As you start trying to solve the problem, you need to know that you’re affecting the system, and if possible, whether you’re making things better or worse. Ask yourself the following questions.

What is actually happening? How is this different to what I expected? When does this behaviour occur? Has it always happened, or did it break? If it broke, did anything change around the time that it broke? Did I change something right before it broke? Often the cause of a problem is the last thing you did before you noticed it. Is there a pattern to when it works and when it doesn’t, like a certain number of repetitions, only during certain times of the day, only after some other event, only in certain environments? If it’s environmental, what’s different between the environments? These questions help us to consider external factors that might be causing the problem. It’s good to get these out of the way first, because there’s no point in wasting your time on trial-and-error if the cause ends up being unrelated to the changes you try making.

6. Were entirely ready to resolve the problem

At this point you should have all the information available to you that might be useful resolving the problem, you have a clear understanding of the precise nature of the problem and what it means for the problem to be resolved, and all that is left is to get into it. You may have found that in running through all the previous steps, you realised what the problem was and you have already figured out how to solve it. Actually this happens so frequently, people gave a name to this phenomenon—rubber ducking. The very act of describing your problem out loud, even to an inanimate object like a rubber duck, often forces you to uncloud your mind and see the problem for what it really is. If you’ve made it this far and you still haven’t solved the problem, it’s finally time to start actually doing something.

7. Humbly remove shortcomings

Start by putting out any current fires—anything that is just going to keep causing more problems while you diagnose. You don’t want people hounding you to hurry up while you’re neck deep in diagnostics, and you don’t want the problem to change or get worse while you’re looking at it. Get the system into a nice, stable, safe state so that you can diagnose the problem in peace.

8. Made a list of all components that are affected, and how we can amend them

Now it’s time to start narrowing down the search space. What components in the system or features in the software are you using? Think about all the behind-the-scenes processes that might also be running in the background, and requests that might be coming in from other systems. Which of them can you reconfigure, to actually make changes to the system? Which of them can you disable to block the number of interactions? Which of them can you step through slowly, verifying after each step that things are looking good? Which of them can you orchestrate manually? What can you reset between each attempt to eliminate the possibility of interaction between attempts? Make an educated guess as to what will happen for each change you could make—try to avoid just making random changes without understanding what you think will happen.

9. Made direct amends to such components wherever possible

Based on your educated guesses, start making some changes. Where possible, try to make only a single change at a time, and monitor to see what effect the change has. If you don’t notice any change, or if the change doesn’t appear to resolve the issue, revert the change and try to get as close to the original state as possible. You want to make sure that when you finally do resolve the issue, you actually know which changes were required. Compare new behaviour, new results and new log entries with those collected during step 4. Compare observed behaviour with what you guessed would happen. Try to be as thorough and systematic as possible, recording your actions and the results. There isn’t really a great deal more general advice I can give on the actions required to resolve arbitrary issues—of course this is going to be far too tightly coupled to the system to be broadly applicable.

10. Continued to take inventory, and when things were off, promptly fixed them

During and after resolving the problem, it’s important to keep gathering as much information as you can to continue monitoring the system. As I said before, often the cause of a problem is the last action you took. You’re now in the action-taking phase, and you want to make sure that if you cause any problems, you see them as quickly as possible. You also want to make sure that you don’t accidentally revert the changes that you made to resolve the problem, causing it to occur all over again. Not to mention that the changes that you made to resolve your problem might interact badly with other parts of the system, causing more problems. Keep an eye on the system until you’re satisfied that everything is stable, and run through any tests or validation steps required to convince yourself that the system is now working correctly.

11. Sought to improve our contact with the system, knowledge and the ability to act on it

Now that you’ve resolved the problem and started to collect information to monitor the system and ensure there are no regressions, it’s time to understand what really went wrong. Sure, there were visible symptoms that you identified in the earlier steps and those have already been resolved, but beneath the surface there’s always a deeper problem and it might still be there, waiting to surface as a new set of symptoms. This could be a lack of understanding of how the components in the system work or interact with each other, a breakdown in a human process that led to the issue, or a gap in monitoring that meant nobody was alerted to the issue early enough. Have a think about other improvements that can be made to prevent this and similar problems from happening again.

12. Having an awakening, we tried to document this knowledge, and practice it in the future

The last step is to document everything you’ve learnt so far. The goal should be to ensure that this problem never happens again, for this environment, for you, and for everybody else who has access to your documentation. If you found any more general improvements to overarching processes or methodologies that could help prevent similar problems too, make sure relevant documentation is updated with the improvements and key learnings. Try to spread the knowledge to others in your organisation or even the wider community (as I’m trying to do now by writing this post). With a small up-front investment of your time in spreading the knowledge, bit by bit we can all work towards eliminating hours of wasted effort diagnosing and resolving known problems with known solutions.

Now that you have enjoyed (hopefully) reading my 12 steps, what are your strategies for resolving issues you encounter?