Lab 18: The ‘Scale’ Command

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The docker-compose scale <service name> = <no of instances> sets the number of containers to run for a service.

NOTE:The scale command is deprecated, instead Use the up command with the –scale flag.
docker-compose up --scale <service name> = <no of instances>

Pre-requisite:

Tested Infrastructure

Platform	Number of Instance	Reading Time
Play with Docker	1	5 min

Pre-requisite

Create an account with DockerHub
Open PWD Platform on your browser
Click on Add New Instance on the left side of the screen to bring up Alpine OS instance on the right side

Assignment

Create a docker-compose.yml file
Bringing up the containers
Listout the services
Scale service

Create a docker-compose.yml file

version: '3.1'
services:
   redis-master:
     image: redis:latest 
     container_name: webserver
     restart: unless-stopped
     ports:
       - "6379"
   redis-slave: 
     image: gcr.io/google_samples/gb-redisslave:v1 
     ports: 
       - "6379"
     environment: 
       - GET_HOSTS_FROM=dns
   frontend: 
     image: gcr.io/google-samples/gb-frontend:v3 
     ports: 
       - "80:80" 
     environment: 
       - GET_HOSTS_FROM=dns

Bringing up the containers

$ docker-compose up -d

Checking container status

$ docker-compose ps
       Name                     Command               State            Ports         
-------------------------------------------------------------------------------------
root_frontend_1      apache2-foreground               Up      0.0.0.0:80->80/tcp     
root_redis-slave_1   /entrypoint.sh /bin/sh -c  ...   Up      0.0.0.0:32769->6379/tcp
webserver            docker-entrypoint.sh redis ...   Up      0.0.0.0:32768->6379/tcp  

Listout the services

$ docker-compose ps --services
redis-slave
frontend
redis-master

Scale service

$ docker-compose scale redis-slave=3
Starting root_redis-slave_1 ... done
Creating root_redis-slave_2 ... done
Creating root_redis-slave_3 ... done

Checking container status

$ docker-compose ps
       Name                     Command                State              Ports         
----------------------------------------------------------------------------------------
root_frontend_1      apache2-foreground               Up         0.0.0.0:80->80/tcp                      
root_redis-slave_1   /entrypoint.sh /bin/sh -c  ...   Up         0.0.0.0:32772->6379/tcp
root_redis-slave_2   /entrypoint.sh /bin/sh -c  ...   Up         0.0.0.0:32775->6379/tcp
root_redis-slave_3   /entrypoint.sh /bin/sh -c  ...   Up         0.0.0.0:32776->6379/tcp
webserver            docker-entrypoint.sh redis ...   Up         0.0.0.0:32768->6379/tcp

NOTE: Host machine can only bind an unallocated port to the container, so trying scale service which is mounted to host will fail.

Lab 18: The ‘Scale’ Command

Pre-requisite:

Tested Infrastructure

Pre-requisite

Assignment

Create a docker-compose.yml file

Bringing up the containers

Checking container status

Listout the services

Scale service

Checking container status

Lab 18: The ‘Scale’ Command

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