Docker Stack

This is used for creating a muiltcontainer architecture using docker compose and deploy it in the swarm cluster.

Docker compose + swarm = docker stack.

Commands

1.To see list of stack

# docker stack ls

2.To create a stck

# docker stack deploy -c stack_filename/docker_composefilename stackname

3.To see list of nodes where the stack service is running

# docker stack ps stackname

4.To see list of services in docker stack

# docker stack service stack_name

5.To delete a stck

# docker stack rm stack_name

Example:

Create a directory==>goinside the directory

Create a yml file ==> vim stack1.yml

---

version: 3

services:

mydb:

image: mysql:5

environment:

MYSQL_ROOT_PASSWORD: edureka

myworsdpress:

image: wordpress

ports:

-5050:80

deploy:

replicas: 3

...

To deploy the stack service

# docker stack deploy -c stack1.yml wordpress

Here -c : allows you to create docker compose file with any name

3.To see where the stack replicas are running

# docker stack ps wordpress

3 replicas of wordpress and 1 mysql replica will be created

4.To remove the stack

# docker stack rm wordpress

Example2:

Starting a jenkins linked with 2 tomcat servers, creating a stack file and adding details like no: of replicas and which service to run on which node

# vim stack2.yml

---

version: 3

services:

jenkins:

image: jenkins

ports:

-5050:8080

deploy:

replicas: 2

placement:

constraints:

-node.hostname == Manager

qaserver:

image: tomcat

ports:

-6060:8080

deploy:

replicas: 2

placement:

constraints:

-node.hostname == Worker1

prodserver:

image: tomcat

ports:

-7070:8080

deploy:

replicas: 3

placement:

constraints:

-node.hostname == Worker2

…

:wq!

# docker stack deploy -c stack2.yml stack-ci-cd

# docker stack ps stackci-cd

So all the replicas will be created will be running on thesre respective manager, worker 1 and worker 2 node as mentioned in stack file

Here under constraints we have give 1 node, but if you want we can give more than 1 node also, so if one node is not available then the service will start running on another node.

If in conatraint you have given only 1 node, then if the node is out of resources or is down, then the services will wait until that node comes alive again.

Example2: Advance:

Create a docker stack file to setup the selenium testing environment and also put an upper limit on the h/w allocation

---

version: '3'

services:

hub:

image: selenium/hub

ports:

-4444:4444

deploy:

replicas: 1

resources:

limits:

cpus: "0.1"

memory: "200M"

chrome:

image: selenium/node-chrome-debug

ports:

-5901:5900

deploy:

replicas: 2

resources:

limits:

cpus: "0.01"

memory: "100M"

firefox:

image: selenium/node-firefox-debug

ports:

-5901:5900

deploy:

replicas: 1

…

2.To deploy the services from above stack file:

# docker stack deploy -c stack3.yml selenium

3.View the services

# docker stack ps selenium