If your application pod use dynamically provisioned glusterfs volumes in your Kubernetes/openshift cluster, it could be that, the volumes are provisioned using `intree` gluster provisioner. Are you confused when I say “intree” ? by `intree` I am talking about the plugin/driver compiled and shipped with kubernetes/openshift release. While using `intree` drivers in the cluster, admin is not worried about how to deploy it, the reason being, by default it is running or registered with Kube API server and listening for persistent volume actions. However Kubernetes sig-storage is also maintaining an external-storage repo which hosts other controllers and provisioners.
External storage repo is not just hosting `external` provisioners, it also hosts other controllers like the snapshot controller. This repo is hosted under incubator and the beauty is that, the flexibility to update the code! If you ever contributed a patch to Kubernetes you would know how difficult it is :), you need to take care of many things including release timelines of kubernetes..etc.
We also had a requirement which has to be quickly satisfied for integrating gluster with one other important project, getting things done at dependent project’s timeline was bit difficult, I would explain what feature we were chasing in my next blog, till then let it hide. To achieve the same we started to implement an external file provisioner for gluster file. We already have an external gluster block provisioner in this same repo, if you are already using gluster block provisioner you know what is external provisioner and how to use it?
The external provisioner for gluster file was merged in external storage repo a couple of months back! You can pull this provisioner and run it in kubernetes/openshift as a pod! The workflow of creating and deleting the persistent volumes remains the same as you use intree plugins or drivers today. The only difference is that you need to mention or use ‘external provisioner’ name in the storage class instead of ‘intree provisioner name’
For example, in Kubernetes/openshift to provision gluster file volumes you would have used provisioner name `kubernetes.io/glusterfs` however in this case, the provisioner name is different and you could use `gluster.org/glusterfile`. The latter name or the external provisioner name is configurable and you can give any name. It’s a configuration parameter which has to be set in your pod template, the provisioner will listen for the requests which match the name specified in the storage class.
Below demo shows how to provision and delete volumes using this external file provisioner. All the artifacts which are used in this demo is available here . Follow this doc for file provisioner deployment .
Demo:
All good, you used external file provisioner and provisioned/deleted gluster file volumes, however, you may have a question comes up to your mind that, why we have one more provisioner for gluster file when we already have intree plugins for provisioner and delete volumes? The answer will be covered in the next blog post on this same topic 🙂
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