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.
Bug Hunt
A 400ms Latency Spike That Turned Out to Be DNS
p99 jumped on one service. The database was fine, every dependency reported healthy, and the flame graph pointed at nothing. That turned out to be the clue.
Kubernetes
OOMKilled: Why Your Container Died and Your Metrics Showed Nothing
Exit code 137, a memory graph that looks perfectly healthy, and no application error. Here is why your monitoring missed it and how to find the real number.
Kubernetes
CrashLoopBackOff: A Complete Diagnostic Flowchart
CrashLoopBackOff is not an error, it is a symptom with about nine distinct causes. Here is how to identify which one you have in under three minutes.
Kubernetes
Debugging DNS Inside Kubernetes When nslookup Lies
nslookup resolves and your application cannot connect. The two use different resolvers, and the difference is where the bug lives.
Docker
Permission Denied in a Container When the File Is Right There
Non root containers break in predictable ways. Here is how UID mapping, volume ownership, and read only filesystems produce the same error.
Docker
Debugging a Container With No Shell, No curl, and No ps
Distroless and scratch images are great for security and miserable when something breaks. Here is how to investigate a container that ships nothing.
Kubernetes
ImagePullBackOff vs ErrImagePull: What Each One Means
Two statuses, one underlying problem, and about six causes. Here is how to read the event message and fix the right thing.