June 26, 2023. Today was another one of those days where you feel like you’re fighting against the entire universe to get something working smoothly. But it’s moments like these that make being an engineer so rewarding.

This morning started off relatively calm, just like any other day. I had a few tickets open from my queue, and I was ready to dive into them. The first ticket was about an unexpected crash in one of our applications, deployed on Kubernetes using a custom WebAssembly (Wasm) module we recently integrated. It’s been a while since we’ve seen issues with Wasm, but these things can happen.

I quickly grabbed the logs and started tracing through the stack frames. The application was running under a busy service, which made it difficult to get any useful information from the crash reports. I spent some time trying to understand where exactly in the code the application failed. As expected, the error message wasn’t very helpful—it just said “Segmentation fault.”

After a few iterations of debugging and refactoring, I realized that the problem might be related to memory allocation in Wasm. The Wasm module we were using was relatively new, so there could be some quirks or bugs lurking around.

I decided to start with the simplest test case: an empty function that simply returns 0. However, even this basic example didn’t work without crashing the application. At this point, I began to feel like a detective trying to solve a mystery with very limited clues.

To narrow down the issue, I turned to some of the newer tools in our arsenal, including Perf and Valgrind, which we had recently started using for better performance and memory analysis. These tools were new to me, but they quickly became my best friends today. With their help, I was able to pinpoint that the crash occurred during a specific function call where we were trying to allocate memory.

The next step was to dig into the Wasm module’s codebase. We had a few different modules from various contributors, so I carefully reviewed each one to see if any of them could be causing the issue. After a bit of back-and-forth and some trial and error, I identified a function that seemed suspiciously prone to memory issues.

I reached out to our developer community on Slack, hoping someone might have encountered something similar before. Within minutes, a colleague chimed in with a suggestion about using a different memory allocation strategy. This gave me the breakthrough I needed. After implementing the change and redeploying, we managed to get through that service without any issues.

Reflecting on this experience, it’s clear that WebAssembly is still an emerging technology, and there are certainly growing pains as we continue to adopt it more widely. But the journey of debugging and refining these tools has been worth it. It’s moments like these that remind me why I chose a career in engineering—to solve problems and push the boundaries of what’s possible.

As I sit here now, reflecting on today’s experience, I can’t help but think about all the discussions around FinOps and cloud cost pressure. While those are valid concerns, they don’t change the fact that our job is to build reliable systems that work for everyone. Today was a reminder that there will always be challenges, but that’s what makes this field so exciting.

In the evening, I plan to share my findings with our team and document everything we’ve learned from this experience. It’s these small victories, both in terms of learning and fixing issues, that make being an engineer such a rewarding career path.