youndie@kotlin.website:~/src$ cat katcher/README.md

katcher

kotlin/native · htmx · sqlite
Self-hosted crash tracker for Kotlin: native binary, HTMX UI, embedded SQLite, and login delegated to whatever proxy already sits in front. Small enough that nobody has to justify running it.
github/katcherread the write-upall libraries

Why it exists

Every crash reporting service wanted one of three things: my data, a JVM with a gigabyte of heap, or a Kubernetes cluster. For a side project — or an internal tool at a company that would rather not ship stack traces to a third party — none of those is a good trade.

What you get

  • One native binary, 30–50 MB resident, starting in milliseconds. scp it to a box and run it.
  • Automatic grouping by fingerprint (message + stack trace), with a dashboard rendered server-side through HTMX — no bundler, no Node in production.
  • Embedded SQLite through sqlx4k. No database to operate.
  • No login screen on purpose. It trusts X-Auth-Request-User and X-Auth-Request-Email from oauth2-proxy, Traefik ForwardAuth or NGINX auth_request, and answers 401 without them. That buys Keycloak, Google or GitHub SSO without a line of OAuth code.

Install

docker run -p 8080:8080 -v ./data:/data ghcr.io/youndie/katcher:latest

Client, in the app you want to hear about:

Katcher.start {
    remoteHost = "https://katcher.example.com"
    appKey = "<YOUR_APP_KEY>"
    release = "1.0.0"
    environment = "Production"
}

One detail worth stealing whatever you use: an atomic guard around the handler, so a crash inside the reporter cannot re-enter it. Without one, a bad day becomes an infinite one.

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