upgrade elastic on docker

 elastic on docker use docker-compose

in docker-compose.yml:

services:
  es31:
    image: docker.elastic.co/elasticsearch/elasticsearch:${VERSION}

in .env file(on same dir)

VERSION=7.7.0

When new release exist,
1- just change the version in file .env
2- stop the docker 
3- start the docker again (docker-compose up es31)

Elasticsearch engine will handle all the process to upgrade. If you has cluster with multiple node, repeat steps above with all the non-master node.  The master node should be the last one.