DellEMC Rex-Ray 0.8 Final Release was announced last week. Graduated as top-level project within {code} community, RexRay 0.8 release has been considered as one of the largest releases till date. The new release introduced support for long lists of new storage platforms like S3FS, EBS, EFS, GCEPD & ScaleIO shown below:
Public cloud storage is one of the fastest growing sector in storage with leaders like Amazon AWS, Google Cloud Storage and Microsoft Azure. With the release of RexRay 0.8, {code} community took the right approach in targeting the first community-contributed driver starting with Amazon EFS driver and then quickly adding additional community-contributed drivers like Digital Ocean, FittedCloud, Google Cloud Engine (GCEPD) & Microsoft Azure Unmanaged Disk driver.
Introducing New Docker 17.03 Volume Plugin System
With Docker 17.03 release, a new managed plugin system has been introduced. This is quite different from the old Docker plugin system. Plugins are now distributed as Docker images and can be hosted on Docker Hub or on a private registry.A volume plugin enables Docker volumes to persist across multiple Docker hosts.
In case you are very new to Docker Plugins, they basically extend Docker’s functionality. A plugin is a process running on the same or a different host as the docker daemon, which registers itself by placing a file on the same docker host in one of the plugin directories described either as a.sock files( UNIX domain sockets placed under /run/docker/plugins), .spec files( text files containing a URL, such as unix:///other.sock or tcp://localhost:8080 placed under /etc/docker/plugins or /usr/lib/docker/plugins)or.json files ( text files containing a full json specification for the plugin placed under /etc/docker/plugin). You can refer this in case you want to develop your own Docker Volume Plugin.
Running RexRay inside Docker container
Yes, you read it correct ! With the introduction of Docker 17.03 New Plugin Managed System, you can now run RexRay inside Docker container flawlessly. Rex-Ray Volume Plugin is written in Go and provides advanced storage functionality for many platforms including VirtualBox, EC2, Google Compute Engine, OpenStack, and EMC.
You can list out available Docker Volume Plugin for various storage platforms using docker search rexray as shown below:
Let us test-drive RexRay Volume Plugin for Swarm Mode cluster for the first time. I have 4-node Swarm Mode cluster running on Google Cloud Platform as shown below:
Verify that all the cluster nodes are running the latest 17.03.0-ce (Community Edition).
Installing the RexRay Volume plugin is just one-liner command:
You can inspect the Rex-Ray Volume plugin using docker plugin inspect command:
It’s time to create a volume using docker volume create utility :
$sudo docker volume create –driver rexray/gcepd –name storage1 –opt=size=32
You can verify if it is visible under GCE Console window:
Let us try running few application which uses RexRay volume plugin as shown:
{code}==>docker run -dit –name mydb -e MYSQL_ROOT_PASSWORD=wordpress -e MYSQL_USER=wordpress -e MYSQL_PASSWORD:wordpress –volume-driver=rexray/gcepd -v dbdata:/var/lib/mysql mysql:5.7
Verify that MySQL service is up and running using docker logs <container-id> command as shown below:
By now, we should be able to see new volume called “dbdata” created and shown under docker volume ls command:
Under GCE console, it should get displayed too:
Using Rex-Ray Volume Plugin under Docker 17.03 Swarm Mode
This is the most interesting section of this blog post. RexRay volume plugin worked great for us till now, especially for a single Docker host running multiple number of services.But what if I want to enable RexRay Volume to persist across multiple Docker Hosts(Swarm Mode cluster)? Yes, there is one possible way to achieve this – using Swarm Executor. It executes docker command across the swarm cluster. Credits to Madhu Venugopal @ Docker Team for assisting me testing with this tool.
Please remember that this is UNOFFICIAL way of achieving Volume Plugin implementation across swarm cluster. I found this tool really cool and hope that it gets integrated within Docker official repository.
First, we need to clone this repository:
$git clone https://github.com/mavenugo/swarm-exec
Run the below command to push the plugin across the swarm cluster:
$cd swarm-exec
$./swarm-exec.sh docker plugin install –grant-all-permissions rexray/gcepd GCEPD_TAG=rexray
First, let’s quickly verify the plugin on the master node as shown below:
While verifying it on the worker nodes:
The docker volume inspect <volname> should display this particular volume as rexray volume driver as shown below:
Creating a MySQL service which uses Rex-Ray volume under Swarm Mode cluster:
Verifying that the service is up and running:
To conclude, the new version of RexRay looks promising and brings support for various Cloud storage platform. It continues to be leading open source container orchestration engine and now with inclusion of Docker 17.03 Managed Plugin architecture, it will definitely reduce the pain for implementing persistent storage solution.
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