Docker
Why Your Docker Build Reinstalls Every Dependency Every Time
One changed byte early in a Dockerfile throws away everything after it. Here is how the cache key is computed and how to order instructions so it survives.
MicroVMs
Debugging Production Without Touching Production
The bug only reproduces with real state. Copying the database loses the parts that matter. Cloning the whole machine keeps them.
DevOps
Consumer Lag Is Not a Throughput Problem Until You Prove It Is
Lag climbing on one partition while the rest keep up tells you something specific. Here is how to read the numbers before you add consumers that cannot help.
Networking
TLS Handshake Failures: the Error the Server Actually Sent
handshake failure, protocol version, unknown ca and bad certificate all mean different things. Here is how to get the real reason out of a connection that…
MicroVMs
The Domain Resolved Everywhere Except Where I Was Sitting
A CNAME that dig confirmed, a browser that refused, and a certificate stuck on pending. Three separate caches pretending to be one problem.
DevOps
Your systemd Service Will Not Start and the Logs Say Nothing
status=203/EXEC, status=217/USER, and the other exit codes that mean something specific. Here is how to read them and what each one actually points at.
MicroVMs
The Test That Only Failed When It Ran Second
A suite that passed alone and failed in the pipeline. The bug was not in the test, it was in what the previous job left behind on the runner.
Networking
Cloudflare 526: The Redirect Loop Behind One Setting
Flexible gives you an infinite redirect. Full strict gives you a 526. The documentation says Full or higher, and higher is the one that breaks.
Node.js
EMFILE: Too Many Open Files, and Why Raising ulimit Is Wrong
The quick fix is raising ulimit. The real question is what is holding thousands of descriptors open and never closing them.
MicroVMs
I Rebooted the VM and the Kernel Did Not Change
A patched kernel that kept reporting the old version after every reboot. The reboot was working perfectly. My assumption about where the kernel comes from…
Bug Hunt
The Outage Caused by a Successful Health Check
Every replica restarted at once during a brief database blip. The health check was working exactly as designed, and the design was wrong.
Docker
exec format error: The ARM64 and AMD64 Mismatch Explained
Your image builds on a Mac and dies in production. What the error means, how to check an image's architecture, and how to build multi arch properly.