Healthcheck

With curl

Health check in docker-compose.yml is usually done as:

docker-compose.yml

healthcheck:
  test: ['CMD', 'curl', '--fail', 'http://localhost:${{ PORT }}${{ ENDPOINT }}']
  interval: 10s
  timeout: 5s
  retries: 5

Without curl (minimal images)

When curl or wget are not available the same can be achieved using the following healthcheck.sh script:

healthcheck.sh

#!/bin/bash

exec 5<> /dev/tcp/localhost/${{ PORT }}
cat <&5 &
printf "GET ${{ ENDPOINT }} HTTP/1.0\r\n\r\n" >&5

Wire it in via a volume mount:

docker-compose.yml

volumes:
  - ./healthcheck.sh:/healthcheck.sh
healthcheck:
  test: ['CMD', '/healthcheck.sh']
  interval: 10s
  timeout: 5s
  retries: 5

Caveats

Caution

This script only verifies that the TCP port is open — it does not inspect the HTTP status code, so it reports healthy even on a 5xx response. It also relies on bash’s /dev/tcp pseudo-device, which is unavailable in sh-only images (Alpine, distroless). For a real HTTP check in a minimal image, prefer a static wget/curl busybox applet or a small compiled probe.