Watchdog Container

docker-compose.yml

x-commonKeys: &commonOptions
  restart: always
  stdin_open: true
  tty: true

x-dnsServers: &dnsServers
  dns:
    - 45.90.28.29
    - 45.90.30.29

services:
  watchdog:
    image: alpine
    container_name: watchdog
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - ./watchdog.sh:/watchdog.sh
    entrypoint: /bin/sh
    command: /watchdog.sh
    <<: [*dnsServers, *commonOptions]

Example Healtcheck

something:
    container_name: something
    image: lscr.io/linuxserver/prowlarr:latest
    ....
    healthcheck:
      test: curl -sf http://localhost || exit 1
      interval: 60s
      timeout: 30s
      retries: 5
      start_period: 30s

watchdog.sh

#!/bin/sh

apk add --no-cache curl bash docker || exit 1

echo "🔍 Watchdog Started. Monitoring Containers..."

while true; do
  unhealthy=$(docker ps --format '{{.Names}}' | while read name; do
    health=$(docker inspect --format='{{if .State.Health}}{{.State.Health.Status}}{{end}}' "$name")

    if [ -z "$health" ]; then
      # Container does not have health check
      return
    fi

    if [ "$health" = "starting" ]; then
      # Container is still starting
      return
    fi

    # Container is unhealthy
    if [ "$health" = "unhealthy" ]; then
      echo "$name"
    fi
  done)

  for c in $unhealthy; do
    echo "[$(date)] 🔁 Restarting Unhealthy Container: $c"

    docker restart "$c"
  done

  sleep 60
done