Initialize Docker Swarm with Ansible
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README.md

ansible-docker-swarm

Setup Docker Swarm with Ansible.

In this setup I have a client node, which will be my jump box, as it will be used to ssh with the docker user to my swarm nodes with passwordless ssh access.

Pre-Check

Hosts file:

$ cat /etc/hosts
10.0.8.2 client
192.168.1.10 swarm-manager
192.168.1.11 swarm-worker-1
192.168.1.12 swarm-worker-2

SSH Config:

$ cat ~/.ssh/config 
Host client
  Hostname client
  User root
  IdentityFile /tmp/key.pem
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Host swarm-manager
  Hostname swarm-manager
  User root
  IdentityFile /tmp/key.pem
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Host swarm-worker-1
  Hostname swarm-worker-1
  User root
  IdentityFile /tmp/key.pem
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Host swarm-worker-2
  Hostname swarm-worker-2
  User root
  IdentityFile /tmp/key.pem
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Install Ansible:

$ apt install python-setuptools -y
$ easy_install pip
$ pip install ansible

Ensure passwordless ssh is working:

$ ansible -i inventory.ini -u root -m ping all
client | SUCCESS => {
    "changed": false, 
    "ping": "pong"
}
swarm-manager | SUCCESS => {
    "changed": false, 
    "ping": "pong"
}
swarm-worker-2 | SUCCESS => {
    "changed": false, 
    "ping": "pong"
}
swarm-worker-1 | SUCCESS => {
    "changed": false, 
    "ping": "pong"
}

Deploy Docker Swarm

$ ansible-playbook -i inventory.ini -u root deploy-swarm.yml 
PLAY RECAP 

client                     : ok=11   changed=3    unreachable=0    failed=0   
swarm-manager              : ok=18   changed=4    unreachable=0    failed=0   
swarm-worker-1             : ok=15   changed=1    unreachable=0    failed=0   
swarm-worker-2             : ok=15   changed=1    unreachable=0    failed=0   

SSH to the Swarm Manager and List the Nodes:

$ docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS      ENGINE VERSION
0ead0jshzkpyrw7livudrzq9o *   swarm-manager       Ready               Active              Leader              18.03.1-ce
iwyp6t3wcjdww0r797kwwkvvy     swarm-worker-1      Ready               Active                                  18.03.1-ce
ytcc86ixi0kuuw5mq5xxqamt1     swarm-worker-2      Ready               Active                                  18.03.1-ce

Create a Nginx Demo Service:

$ docker network create --driver overlay appnet
$ docker service create --name nginx --publish 80:80 --network appnet --replicas 6 nginx
$ docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE               PORTS
k3vwvhmiqbfk        nginx               replicated          6/6                 nginx:latest        *:80->80/tcp

$ docker service ps nginx
ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS
tspsypgis3qe        nginx.1             nginx:latest        swarm-manager       Running             Running 34 seconds ago                       
g2f0ytwb2jjg        nginx.2             nginx:latest        swarm-worker-1      Running             Running 34 seconds ago                       
clcmew8bcvom        nginx.3             nginx:latest        swarm-manager       Running             Running 34 seconds ago                       
q293r8zwu692        nginx.4             nginx:latest        swarm-worker-2      Running             Running 34 seconds ago                       
sv7bqa5e08zw        nginx.5             nginx:latest        swarm-worker-1      Running             Running 34 seconds ago                       
r7qg9nk0a9o2        nginx.6             nginx:latest        swarm-worker-2      Running             Running 34 seconds ago   

Test the Application:

$ curl -i http://192.168.1.10
HTTP/1.1 200 OK
Server: nginx/1.15.0
Date: Thu, 14 Jun 2018 10:01:34 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 05 Jun 2018 12:00:18 GMT
Connection: keep-alive
ETag: "5b167b52-264"
Accept-Ranges: bytes

Delete the Swarm:

$ ansible-playbook -i inventory.ini -u root delete-swarm.yml 

PLAY RECAP 
swarm-manager              : ok=2    changed=1    unreachable=0    failed=0   
swarm-worker-1             : ok=2    changed=1    unreachable=0    failed=0   
swarm-worker-2             : ok=2    changed=1    unreachable=0    failed=0   

Ensure the Nodes is removed from the Swarm, SSH to your Swarm Manager:

$ docker node ls
Error response from daemon: This node is not a swarm manager. Use "docker swarm init" or "docker swarm join" to connect this node to swarm and try again.

Thanks a lot to lucj, make sure to checkout his repo.