Scale multiple containers of a service in a single host - performance

Question

I am scaling multiple containers of a service on a single linux host by command "docker-compose up --scale". However, each container can use all the resources (CPU and RAM) of the host. It seems to be useless to scale like that.
Thus, I try to limit availabe CPU and RAM for each container (I am currently using docker-compose version 2) by "cpus" and "mem_limit" tag in docker-compose.yml file.
This is my docker-compose.yml file
version: "2.2"
services:
test:
image: test
mem_limit: 500000000
container_name: test
build: ./test
restart: always
mem_limit: 500000000
mem_reservation: 300m
cpus: 0.5
networks:
- test-network
ports:
- "9000:80"
But I don't know that if it is useful to scale multiple containers of a service on a single host? Also, is there any ways to automatically scale this service (scale on demand)?
Thank you,

Answer 1

version: "3"
services:
test:
image: test
deploy:
replicas: 5
resources:
limits:
cpus: "0.5"
memory: 500M
restart_policy:
condition: always
ports:
- "9000:80"
networks:
- test-network
networks:
test-network:
docker swarm init #Initialize machine as docker swarm manager
docker stack deploy -c docker-compose.yml testing #This will start 5 containers for the same image as replica
You can scale the app by changing the replicas to 6 value in docker-compose.yml, saving the change, and re-running
docker stack deploy -c docker-compose.yml testing #Docker performs an in-place update, no need to tear the stack down first or kill any containers
For detailed explanation you can follow this article, https://docs.docker.com/get-started/part3/.
But i suggest you to start with first part of this tutorial.
And for any docker experiments you can try https://labs.play-with-docker.com/