Friday, February 07, 2020

Adventures in Code Spelunking


It started innocently enough. I had an Azure DevOps Test Plan that I wanted to associate some automation to. I’d wager that there are only a handful of people on the planet who’d be interested by this, and I’m one of them, but the online walk-throughs from Microsoft’s online documentation seemed compatible with my setup – so why not? So, with some time in my Saturday afternoon and some horrible weather outside, I decided to try it out. And after going through all the motions, my first attempt failed spectacularly with no meaningful errors.

I re-read the documentation, verified my setup and it failed a dozen more times. Google and StackOverflow yielded no helpful suggestions. None.

It’s the sort of problem that would drive most developers crazy. We’ve grown accustomed to having all the answers a simple search away. Surely others have already had this problem and solved it. But when the oracle of all human knowledge comes back with a fat goose egg you start to worry that we’ve all become a group of truly lazy developers that can only find ready-made code snippets from StackOverflow.

When you are faced with this challenge, don’t give up. Don’t throw up your hands and walk away. Surely there’s an answer, and if there isn’t, you can make one. I want to walk you through my process.

Read the logs

If the devil is in the details, surely he’ll be found in the log file. You’ve probably already scanned the logs for obvious errors, it’s okay to go back and look again. If it seems the log file is gibberish at first glance, it often is. But sometimes the log contains some gems that give clues as to what’s missing. Maybe the log warns that a default value is missing, maybe you’ll discover a typo in a parameter.

Read the logs, again

Amp up the verbosity on the logs if possible and try again. Often developers use the verbose logging to diagnose problems that happen in the field, so maybe the hidden detail in the verbose log may reveal further gems.

Now’s a good moment for some developer insight. Are these log messages helpful? Would someone reading the logs from your program be as delighted or frustrated with the quality of these output messages?

Keep an eye out for references to class names or methods that appear in the log or stack traces. These could lead to further clues or give you a starting point for the next stage.

Find the source

Microsoft is the largest contributor to open-source projects on Github than anyone else, so it makes sense that they bought them. Just watching the culture shift within Microsoft in the last decade has been astounding and now it seems that almost all of their properties have their source code freely available for public viewing. Some sleuthing may be required to find the right repository. Sometimes it’s as easy as Googling “<name-of-class> github” or following the link on a nuget or maven repository.

But once you’ve found the source, you enter a world of magic. Best case scenario, you immediately find the control logic in the code that relates to your problem. Worse case scenario, you learn more about this component than anyone you know. Maybe you’ll discover they parse inputs as case sensitive strings, or some conditional logic requires the presence of a parameter you’re not using.

Within Github, your secret weapon is the ability to search within the repository, as you can find the implementation and usages in a single search. Recent changes within Github’s web-interface allows you to navigate through the code by clicking on class and method names – support is limited to specific programming languages but I’ll be in heaven when this capability expands. The point is to find a place to start and keep digging. It’ll seem weird not being able to set a breakpoint and simply run the app, but the ability to mentally trace through the code is invaluable. Practice makes perfect.

If you’re lucky, the output from the log file will help guide you. Go back and read it again.

As another developer insight – this code might be beautiful or make you want to vomit. Exposure to other approaches can validate and grow your opinions on what makes good software. I encourage all developers to read as much code that isn’t theirs.

After spending some time looking at the source, check out their issues list. You might discover your problem is known by a different name that is only familiar to those that wrote it. Alternative suitable workarounds might appear from other problems.

Roadblocks are just obstacles you haven’t overcome

If you hit a roadblock, it helps to step back and think of other ways of looking at the problem. What alternative approaches could you explore? And above all else, never start from a position where you assume everything on your end is correct. Years ago when I worked part-time at the local computer repair shop, I learnt the hard way that the easiest and most blatantly obvious step, checking to see if it was plugged in, was the most important step to not skip. When you keep an open-mind, you will never run out of options.

As evidenced by the tweet above, the error message I was experiencing was something that had no corresponding source-code online and all of my problems were baked into a black-box that only exists on the build server when the build runs. When the build runs… on the build server. When the build runs on the build agent… that I can install on my machine. Within minutes of installing a local build agent, I had the mysterious black-box gift wrapped on my machine.

No source code? No problem. JetBrain’s dotPeek is a free utility that allows you to decompile and review any .net executable.

Just dig until you hit the next obstacle. Step back, reflect. Dig differently. As I sit in a coffee shop looking out at the harsh cold of our Canadian winter, I reflect that we have it so easy compared to the original pioneers who forged their path here. That’s who you are, a pioneer cutting a path that no one has tread before. It isn’t easy, but the payoff is worth it.

Happy coding.