Rob Ferguson

Setting up Docker Swarm Mode on my Raspberry Pi 3 PicoCluster

Rob Ferguson -

In a previous post, I wrote about setting up my Raspberry Pi 3 PicoCluster.

In this post, I'll walk you through the steps I followed when setting up Docker Swarm Mode on my Raspberry Pi 3 PicoCluster.

Install Docker

We can download the latest .deb package (for the RPi 3's ARM architecture) from Docker's packagecloud.io repo:

wget https://apt.dockerproject.org/repo/pool/main/d/docker-engine/docker-engine_1.12.3-0~jessie_armhf.deb

And, copy (scp) it to each node:

export FILE=docker-engine_1.12.3-0~jessie_armhf.deb
export USER=picocluster
scp $FILE $USER@pc0:$FILE
scp $FILE $USER@pc1:$FILE
scp $FILE $USER@pc2:$FILE
scp $FILE $USER@pc3:$FILE
scp $FILE $USER@pc4:$FILE

Now, we can install Docker and add the "picocluster" user to the Docker group (repeat for each node):

ssh manager sudo apt install libapparmor1
ssh manager sudo dpkg -i $FILE
ssh manager sudo usermod -aG docker $USER

Note: In a previous post, I setup a SSH configuration file to save key strokes and to make things much easier to remember.

Check that everything is OK:

ssh manager
docker version

You should see output like:

Create a swarm

Now, we can bootstrap the manager node:

docker swarm init

You should see output like:

Check that everything is OK:

docker node ls

You should see output like:

To join the swarm as a worker we first need to retreive the join token for worker nodes (from the manager node):

docker swarm join-token --quiet worker

You should see output like:

SWMTKN-1-0ul3khhcxl0mbgw46j91q300z0h3hkd22efoz61jradxkedecm-4nuzigyociikgwzdttaqbm0dc

Now, we can bootstrap some worker nodes:

function getip() { (traceroute $1 2>&1 | head -n 1 | cut -d\( -f 2 | cut -d\) -f 1) }
export TOKEN=SWMTKN-1-0ul3khhcxl0mbgw46j91q300z0h3hkd22efoz61jradxkedecm-4nuzigyociikgwzdttaqbm0dc
export MANAGER_IP=$(getip pc0)
export PORT=2377
ssh worker-1 docker swarm join --token $TOKEN $MANAGER_IP:$PORT
ssh worker-2 docker swarm join --token $TOKEN $MANAGER_IP:$PORT
ssh worker-3 docker swarm join --token $TOKEN $MANAGER_IP:$PORT
ssh worker-4 docker swarm join --token $TOKEN $MANAGER_IP:$PORT

To view the current state of the swarm:

docker info

You should see output like:

Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 0
Server Version: 1.12.3
...
Swarm: active
 NodeID: 894zvyqhzy395mt3jogw2g14s
 Is Manager: true
 ClusterID: 5bxf4abzgdfbao2q70owqm4bh
 Managers: 1
 Nodes: 5
...

To view information about nodes:

docker node ls

You should see output like:

Deploy a service to the swarm

Now, lets bring up a container:

docker service create --replicas 1 --name ping hypriot/rpi-alpine-scratch ping docker.com

To see a list of running services:

docker service ls

You should see output like:

To scale up the number of tasks:

docker service scale ping=10

You should see output like:

To list a service's tasks:

docker service ps ping

You should see output like:

To remove the service:

docker service rm ping

Way cool :)

References: