I need to start multiple containers for the same image. If I create my compose file as shown below, it works fine.
version: '2'
services:
app01:
image: app
app02:
image: app
app03:
image: app
app04:
image: app
app05:
image: app
Is there an easy way for me to mention the number of instances for the compose instead of copy and pasting multiple times?
The old "scale" feature is now called replicas and it is part of the current Docker Compose specs, 2.19.1 as of writing.
Note that replicas is ignored if you name your container using container_name: myname. You must let the Docker generate the names.
services:
myapp:
image: awesome/webapp
deploy:
mode: replicated
replicas: 6
As others mentioned, the Docker API has changed. I'm updating my answer since it's the one most people will probably look at.
docker-compose up -d --scale app=5
Unfortunately, we cannot specify this in a docker-compose.yml file currently as of version 3.5 (1.18.0 in re-numbered version).
Details:
They did introduce the scale option for version 2.2 and 2.3 of docker-compose, but they removed it for version 3.0. Also, to use version 2.2 or 2.3 you would need to download an older version of the docker-compose tool. The current version does not support 2.2 or 2.3 (it does support 2.0 or 2.1 however).
There is also a new deploy section with replicas: 5 but it's only for swarm mode.
docker-compose scale app=5
See docker compose up.
Then you only need this docker-compose file:
version: '2'
services:
app:
image: app
docker-compose up, it will run the preconfigured number of instances?
expose: for exposing ports to other services on the same network or ports: to expose ports to the host (publicly accessible). docs.docker.com/compose/compose-file/#short-syntax-1
-d (daemon mode) means all containers started using the same docker-compose file will stop once Ctrl+C is used to terminate the last scaled container. Very dangerous. I'd suggest adding -d to docker-compose up in the answer above, to avoid copy/paste disasters.up -d. Typo this time.You can do it with replica as mentioned in Compose specification:
version: '3'
services:
worker:
image: dockersamples/examplevotingapp_worker
networks:
- frontend
- backend
deploy:
mode: replicated
replicas: 6
One can use docker-compose --compatibility up to make Docker accept a deploy section without using swarm.
docker-compose up commands.
deploy intro/header docs state that the entire section is ignored by docker-compose up (docs.docker.com/compose/compose-file/#deploy)
docker-compose --compatibility up to make docker accept deploy section without using swarm.
The scale command is now deprecated, and you should use up instead.
docker-compose up --scale app=2
More details are on docker compose up.
docker-compose up --scale appB=2 appB to only start service B. I normally do docker-compose up then if I want additional instances of a particular service I follow up with docker-compose up --scale appB=5 appBYou can do this:
version: "3.4"
services:
service1: &service_1
image: app
service2:
<<: *service_1
service3:
<<: *service_1
For more information on <<, see What is the << (double left arrow) syntax in YAML called, and where's it specified?.
expose port, the other containers will not able to connect via service discovery.
Works for me well:
version: "3.9"
services:
web:
image: redis:6.2-alpine
...
deploy:
mode: replicated
replicas: 3
and run the command then:
docker-compose --compatibility up