Introduction
Context reminder
Today, a new part of my homelab posts serie :). In the first post, I’ve explained my architecture choices for my 4 Raspberry Pi cluster. In the second, I’ve setup a GlusterFS replicated volumes on all my servers in order to have a shared folders between them (so you don’t care where containers are created).
In this post, I’ll talk about the initial docker swarm setup.
Assumptions
I have 4 Raspberry Pi, all having a /mnt/cluster-data
GlusterFS volume mounted so that any files in
there will be replicated on all Pis.
As a reminder, my 4 Raspberry Pi are named
cell, ptitcell1, ptitcell2, ptitcell3. For GlusterFS, they all have
the same roles, but not for our docker swarm cluster, so pay attention
to the servers name :).
For the rest of the article, you should have an understanding of what docker, containers or a cluster are. You should also know your way a little navigating in a linux terminal. If not, go read some documentation first :).
Docker Swarm setup:
Definition
Docker Swarm1: > A swarm consists of multiple Docker hosts which run in swarm mode and act as managers (to manage membership and delegation) and workers (which run swarm services). A given Docker host can be a manager, a worker, or perform both roles.
Docker Swarm Node(s)2: > A node is an instance of the Docker engine participating in the swarm.
Docker Swarm Manager(s)3: > Dispatches units of work called tasks to worker nodes.
Docker Swarm Worker(s)4: > Receive and execute tasks dispatched from manager nodes.
My choices
I decided to setup a cluster with 1 manager node and 3 workers nodes. You can choose a different setup with multiple manager if you want but in this case adapt the following steps to your situation. I might later on change this, it isn’t complex to add a new manager or workers later on if needed.
Installation
Ok, let’s go then :)
First, install docker on all the pi5:
curl -sSL https://get.docker.com | sh;
sudo usermod -aG docker pi
Then, on the manager node (cell in my case):
docker swarm init --advertise-addr <CellIpAddress> --default-addr-pool 10.10.0.0/16
Replace <CellIpAddress> by the local IP address of your node manager.
The --default-addr-pool is optional and is needed only if it conflicts
with other network6.
On all the other nodes of our cluster (for me: ptitcell{1,2,3}):
docker swarm join --token <token> <CellIpAddress>:2377
Replace <CellIpAddress> by the local IP address of your node manager.
And that should do it for basic setup, it’s that simple :)
Testing
Now, let’s start a simple container to see if this is working as expected. Let’s start a very simple container that create a simple webpage to visualize our containers. For this, we will use alexellis2/visualizer-arm.
docker service create \
--name viz \
--publish 8080:8080 \
--constraint node.role==manager \
--mount type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock \
alexellis2/visualizer-arm:latest
Now you can open a browser and go to http://<CellIpAddress>:8080
Finally, let’s transform this in a docker-compose.yml as this will be
the format I will use to define all my services later on.
I’m saving all my services config files (docker-compose.yml) in
/mnt/cluster-data/services-config/<nameOfTheService>, so in this case,
I’m creating a
/mnt/cluster-data/services-config/vizualizer/docker-compose.yml with
the following content:
version: "3"
services:
viz:
image: alexellis2/visualizer-arm:latest
volumes:
- "/var/run/docker.sock:/var/run/docker.sock"
ports:
- "8080:8080"
deploy:
placement:
constraints:
- node.role == manager
And start it with the following command:
docker stack deploy viz -c /mnt/cluster-data/services-config/visualizer/docker-compose.yml
Now you can go back to http://<CellIpAddress>:8080 to check if
everything is still working!
...
deploy:
placement:
constraints:
- node.role == manager
↑ This part is to force the container to be started on the docker swarm manager node.
If everything is working fine, you now have a docker swarm cluster setup
and ready to manage services! We’ll go through this in our next post. In
the meantime, you can stop and remove the viz stack:
docker stack rm viz
To be Continued… :-)
Now we have a very basic docker swarm setup working and ready to manage stack, services and containers :) … But that will be in my next blog post where we’ll start managing real services, with traefik 2 as a reverse proxy with automated redirection to https and automatic ssl via letsencrypt.
In this blog posts serie:
You can follow all posts about my Home Lab setup on the dedicated page.
In the Home Lab setup series:
To Do
To be writen: Monitoring, Backups, Tests environment, …