Docker Healthchecks

Rationale

Use these to verify the health of database containers. This allows me to only run web services when a database is healthy. This prevents us from hiding a silent failure.

MariaDB

healthcheck:
  test: ["CMD", "healthcheck.sh", "--connect", "--innodb_initialized"]
  start_period: 10s
  interval: 10s
  timeout: 5s
  retries: 3

MySQL

healthcheck:
  test: ["CMD", "mysqladmin" ,"ping", "-h", "localhost"]
  timeout: 20s
  retries: 10

Postgres

healthcheck:
  test: ["CMD", "pg_isready", "-U", "<user>"]
  interval: 30s
  timeout: 20s
  retries: 3    

Web Services

healthcheck:
  test: ["CMD-SHELL", "curl -f http://localhost:3000/api/healthz | grep pass"]
  interval: 1m
  timeout: 2m
  retries: 5
   

If the service has an HTTP endpoint and has the curl binary, use the above to create a healthcheck.

Use CMD-SHELL as the first token to be able to pipe output from curl to grep

Valkey

healthcheck:
  test: ["CMD-SHELL", "valkey-cli ping | grep PONG"]
  start_period: 20s
  interval: 30s
  retries: 5
  timeout: 3s