docker-compose v2.1 healthcheck and service_healthy

docker-compose.yml

version: '2.1'
services:
   web:
     image: nginx:alpine
     depends_on:
       db:
         condition: service_healthy
   db:
     image: redis:alpine
     healthcheck:
        test: ["CMD", "redis-cli","ping"]
        interval: 30s
        timeout: 10s
        retries: 3