Prevent provisioning of persistent volumes on nodes with an empty paths list

[Exagone313]

Hi,

I have a cluster with two nodes:

• the first node is home to deployments using local-path-provisioner (aka first.example)
• the second node (aka second.example) was recently added to try to add room for deployments that do not need a persistent volume.

local-path-provisioner has been configured to have an empty paths list for nodes others that the first node:

    {
            "nodePathMap":[
            {
                    "node":"DEFAULT_PATH_FOR_NON_LISTED_NODES",
                    "paths":[]
            },
            {
                    "node":"first.example",
                    "paths":["/opt/local-path-provisioner"]
            }
            ]
    }

However, it seems that local-path-provisioner is trying to create persistent volumes on the second node:

error syncing claim "e0b17b36-47e5-416f-a4c7-5eada4db8165": failed to provision volume with StorageClass "local-path": no local path available on node second.example

My guess is that local-path-provisioner is not responsible for that choice, and that it's just a "fail-safe".

If one node is listed but with paths set to [], the provisioner will refuse to provision on this node.

The node is selected by the scheduler for the volume:

/* vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/controller/volume.go */

// ProvisionOptions contains all information required to provision a volume
type ProvisionOptions struct {
	 /* ... */
	// Node selected by the scheduler for the volume.
	SelectedNode *v1.Node
}

But the pod that interacts with the persistent volume claim is not yet scheduled on a node (status Pending), maybe Kubernetes misses a mechanism for solving such case.

With a nodeSelector on the pod, the persistent volume is correctly created.

If I am correct, this issue can be converted into a documentation issue and I'm willing to add a sentence for that case.

---

• Kubernetes v1.18.9
• rancher/local-path-provisioner:v0.0.17

[innobead]

Yes, local-path-provsioner adopts WaitForFirstConsumer volume binding mode to wait for the consumer pod arranged. This is the native behavior of dynamic provision.

We will enhance the README a bit to make sure the case clear for the users, also welcome to contribute!

[ErikLundJensen]

I suggest that you use the nodeSelector on the DaemonSet to install the provisioner only at the nodes that actually has local storage.

[plasorak]

Hi, I'm running in the same issue.

I suggest that you use the nodeSelector on the DaemonSet to install the provisioner only at the nodes that actually has local storage.

Could you be a bit more precise? Which DeamonSet are you talking about?

I'm not sure I understand why putting a path: [] for the default nodes shouldn't work. Am I correct in assuming that if you created manually a pair of PV/PVC, the pod that uses it will run on a node which is able to satisfy this claim? If so why shouldn't this work? I'd like to avoid having to use the nodeSelector on my pod.