Health Check Setup

Intermediate10 min

Configure container health checks so Docker can automatically detect unhealthy containers and orchestrators can restart them.

Prerequisites

-Docker installed

Steps

Add HEALTHCHECK to a Dockerfile

Define a health check command that Docker runs periodically to determine if the container is healthy.

$ echo 'HEALTHCHECK --interval=30s --timeout=10s --retries=3 CMD curl -f http://localhost:3000/health || exit 1'

Adjust interval and timeout based on your application's startup time and response characteristics.

Add health check in Docker Compose

Configure health checks in your compose file for each service.

$ cat <<'EOF' services: api: image: myapp:latest healthcheck: test: ["CMD", "curl", "-f", "http://localhost:3000/health"] interval: 30s timeout: 10s retries: 3 start_period: 40s EOF

Check container health status

View the health status and recent health check results.

$ docker inspect <container-name> --format '{{.State.Health.Status}}: {{range .State.Health.Log}}{{.Output}}{{end}}'

View health check history

See the last few health check results including timestamps and output.

$ docker inspect <container-name> --format '{{json .State.Health}}' | jq '.Log[-3:]'

Full Script

full-script.sh

#!/bin/bash
# Health Check Setup and Verification
set -euo pipefail

echo "=== Container Health Status ==="
docker ps --format 'table {{.Names}}\t{{.Status}}'

echo ""
echo "=== Detailed Health for All Containers ==="
for container in $(docker ps -q); do
  name=$(docker inspect "$container" --format '{{.Name}}' | sed 's/\///')
  health=$(docker inspect "$container" --format '{{if .State.Health}}{{.State.Health.Status}}{{else}}no healthcheck{{end}}')
  echo "$name: $health"
done

FAQ

Discussion

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#!/bin/bash # Health Check Setup and Verification set -euo pipefail echo "=== Container Health Status ===" docker ps --format 'table {{.Names}}\t{{.Status}}' echo "" echo "=== Detailed Health for All Containers ===" for container in $(docker ps -q); do name=$(docker inspect "$container" --format '{{.Name}}' | sed 's/\///') health=$(docker inspect "$container" --format '{{if .State.Health}}{{.State.Health.Status}}{{else}}no healthcheck{{end}}') echo "$name: $health" done