Networking
x509: certificate signed by unknown authority
Your browser trusts the certificate and your application does not. They use different trust stores, and inside a container there may not be one at all.
Rohit Bhadani
I write about why software breaks and how people figure it out. Founder of Krova Cloud, building isolated microVMs on our own hypervisor. Years of Shopify theme work and shared hosting before that. If I have not reproduced it, I do not publish it.
Debugging
Your Flaky Tests Are Not Flaky, They Are Telling You Something
A test that fails one time in fifty is reporting a real property of your system. Retrying it is throwing away the evidence.
React
Too Many Re-renders: Finding the Infinite Loop in React
React caught the loop and stopped it. Here are the five ways to create one and how the Profiler tells you which you have.
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.
DevOps
Your CI Cache Is Making Builds Slower and Occasionally Wrong
A cache with the wrong key restores nothing and uploads everything. A cache with too broad a key restores stale artifacts. Both are common.
JavaScript
Unexpected token < in JSON at position 0 Means You Got HTML
The angle bracket is the first character of an HTML error page. Your API returned a page, not JSON, and here is how to find out which page.
Networking
Your Cache-Control Header Is Probably Wrong
no-cache does not mean do not cache. max-age on a CDN is not what you think. Here is what each directive actually does.
JavaScript
No Access-Control-Allow-Origin: What CORS Is Really Doing
CORS errors are a browser protecting you from a response it already received. Understanding that one fact makes every CORS error obvious.
Tooling
fatal: refusing to merge unrelated histories
Git is protecting you from combining two repositories that share no common ancestor. Sometimes that is exactly what you want.
Docker
Containers Share a Kernel and That Is the Whole Story
The difference between a container and a microVM is one sentence long, and almost every isolation decision follows from it.
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.
Node.js
Finding a Node.js Memory Leak With Heap Snapshots
Memory climbs, the process gets killed, and restarting fixes it for six hours. Here is the diff based method that finds the retainer.