This article is PART 2 of a series on Dockerizing your own personal infrastructure (Docker Swarm, RexRay, Traefik, Let’s Encrypt, DigitalOcean, Jenkins, Ansible)
REX-Ray enables stateful applications, such as databases, to persist and maintain its data after the life cycle of the container has ended. Built-in high availability enables orchestrators such as Docker Swarm, Kubernetes, and Mesos Frameworks like Marathon to automatically orchestrate storage tasks between hosts in a cluster.
In order to set up volume persistence for your data, you will need to install a docker storage plugin. After some failed attempts I have settled on rex-ray as it integrates with all the big cloud providers. Rexray can run both as a standalone service and as a docker plugin, but it was easier for me to configure it as a docker plugin.
In order to install the docker plugin and configure it to use Digital Ocean block storage you will need a Digital Ocean access token.
The following command should be run on all nodes in the swarm ( both managers and workers )
docker plugin install rexray/dobs DOBS_TOKEN=aaabbbcccdddeeefff DOBS_REGION=ams3 LINUX_VOLUME_FILEMODE=0775
This command installs RexRay as a docker plugin with the Digital Ocean token provided, allowing it to connect to the Digital Ocean api and manage your block storage, and with the droplet region you are using. I am not sure why this is required, but i assume the Digital Ocean api requires the droplet region for some of the methods used.
The filemode parameter is useful depending on the permissions your data required.
The parameter LIBSTORAGE_VOLUME_OPERATIONS_MOUNT_ROOT_PATH can be used in order to mount the data inside a specified subdirectory of the volume.
Now we can create the volume on the manager. The size option tells rexray to create a digital ocean block storage of 1GB and attach it to your manager. Your swarm workers will automatically have access to it as well
docker volume create --name=mynewvolume --opt=size=1 --driver=rexray/dobs
Now in your docker-compose.yml file for your stack, you will need to add the external volume and reference it
version: '3.3' volumes: mynewvolume: external: true services: db: image: mysql:5.7 volumes: - mynewvolume:/var/lib/mysql
One limitation i have found is that you can attach a maximum of 7 block storage volumes to a droplet.
For more info, here’s a link to the official documentation for RexRay RexRay Docs — RexRay Digital Ocean Provider Docs.
The following article in the series contains information on how to deploy container stacks to a docker swarm using Ansible and Jenkins