Checking PostgreSQL health for dependent services in docker-compose (for e.g. Grafana)

docker-compose.yml

x-pg-healthcheck: &pg-healthcheck
  healthcheck:
    test: ["CMD-SHELL", "pg_isready -U postgres"]
    interval: 5s
    timeout: 5s
    retries: 5

x-pg-config: &shared-pg-config
  image: postgres:13.0-alpine
  restart: 'unless-stopped'

version: '3.8'
services:
  postgres:
    <<: *shared-pg-config
    ports:
    - '5432:5432'
    environment:
      POSTGRES_DB: grafana
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres-changeme
    volumes:
      - ./data/postgres-grafana:/var/lib/postgresql/data:delegated
    <<: *pg-healthcheck
  ev-warehouse:
    <<: *shared-pg-config
    ports:
    - '5433:5432'
    environment:
      POSTGRES_DB: ev-analytics-warehouse
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres-changeme
    volumes:
      - ./data/postgres-ev-warehouse:/var/lib/postgresql/data:delegated
    <<: *pg-healthcheck
  grafana:
    build: .
    restart: 'unless-stopped'
    ports:
      - '3000:3000'
    environment:
      DB_HOST: postgres:5432
      DB_NAME: grafana
      DB_USER: postgres
      DB_PASS: postgres-changeme
      WAREHOUSE_DB_HOST: ev-warehouse:5432
      WAREHOUSE_DB_NAME: ev-analytics-warehouse
      WAREHOUSE_DB_USER: postgres
      WAREHOUSE_DB_PASS: postgres-changeme
    depends_on:
      postgres:
        condition: service_healthy
      ev-warehouse:
        condition: service_healthy
    links:
      - postgres