Docker Swarm Persistent Storage Using GlusterFS

Running stateful applications on Docker Swarm is a bit tricky since docker volumes are created on the server where the container runs. When the container is moved to a different server, data will will be inaccessible. Using GlusterFS is a solution for this problem. Through this article you will find simple and easy way to create GlusterFS Cluster. Creating Docker Swarm cluster is out of scope of this document.

I assume that you already have Docker Swarm cluster running:

root@akaftan0:/opt# docker node ls
ID        HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
gpd1zhyjpdekx8i0ogxrr9fsv *  akaftan0 Ready  Active  Leader 19.03.8
u9t8s7nsjscnw9qcpicrd3104    akaftan1 Ready  Active         19.03.8

1. Install GlusterFS

sudo apt-get install software-properties-common -y
sudo add-apt-repository ppa:gluster/glusterfs-3.12
sudo apt-get update
sudo apt install glusterfs-server -y
sudo systemctl start glusterd
sudo systemctl enable glusterd

2. Generate SSH Keys

ssh-keygen -t rsa

3. Probe Nodes

Please make sure that servers can resolve their names.

root@akaftan0:/opt# gluster peer probe akaftan1

4. Check GlusterFS Pool

root@akaftan0:/opt# gluster pool list
UUID                                    Hostname   State
a54e256b-f0c2-4963-9b3c-a3438ef5f11e    akaftan1   Connected
d953dda7-f8ea-4bf6-ad2f-b6cffb01d745    localhost  Connected

5. Create the GlusterFS Volume

sudo mkdir -p /opt/mnt-vol
sudo gluster volume volume-data akaftan0:/opt/mnt-vol akaftan1:/opt/mnt-vol force
gluster volume start volume-data
echo 'localhost:/volume-data /opt/mnt glusterfs defaults,_netdev,backupvolfile-server=localhost 0 0' >> /etc/fstab
mount.glusterfs localhost:/volume-data /opt/mnt

6. Create Directory

mkdir -p /opt/mnt/cassandra-data

7. Deploy Your Stateful Application

version: '3.7'
services:
  cassandra:
    image: cassandra:3.11.6
    ports:
      - "9042:9042"
    restart: unless-stopped
    volumes:
      - /opt/mnt-vol/cassandra-data:/var/lib/cassandra/data
networks:
  default:
    driver: "overlay"

Now, enjoy your stateful application on Docker Swarm.