Komorebi is a lightweight netcat-based HTTP server written in Bash. It was written to solve this situation:
- You have service A running on a machine that has an HTTP interface for health checking
- Service A's health check always returns an HTTP response code of 200 regardless of health (but returns descriptive data in the HTTP body)
- Service B does HTTP health checks on service A and determines health by HTTP response code
Thus, Service B considers Service A as "healthy" even if A's health check HTTP body is:
{ "status": "Completely Dead" }
Komorebi can help here because it supports arbitrary commands and translates the exit code into one of two HTTP responses:
- 200 OK
- 500 Internal Error
Komorebi has only one requirement: that nc is available somewhere in your $PATH. You can install it with:
apt-get install netcat-openbsd
The traditional netcat package doesn't seem to behave correctly, so make sure you get the openbsd version.
If netcat-openbsd isn't installed, Komorebi will automatically try to install it if it can find apt-get. It assumes you are root (Heh, sorry...).
Here's one way of using Komorebi:
$ COMMAND='curl -s localhost:9200/health-check | grep -q GOOD' PORT=3000 ./komorebi
Starting Komorebi HTTP server on port 3000
Command: 'curl -s localhost:9200/health-check | grep -q GOOD'
Komorebi will return 200 if the body of the health check on port 9200 has the word "GOOD" in it. Otherwise it will return a 500.
If you don't have git, you can just:
$ curl 'https://raw.githubusercontent.com/heepster/komorebi/master/komorebi' | COMMAND='<command>' PORT='<port>' bash
Here are the default values Komorebi will use if you don't specify:
COMMAND: 'date'
PORT: 1500