linstor-scheduler-extender

LINSTOR scheduler extender plugin for Kubernetes which allows a storage driver to give the Kubernetes scheduler hints about where to place a new pod so that it is optimally located for storage performance.

Get started

If you want to get started directly with an existing LINSTOR setup, check out the single file deployment The deployment will create:

• All needed RBAC resources
• A Deployment spawning 2 replicas of the Kube-scheduler with linstor-scheduler-existing, configured to connect to http://piraeus-op-cs.default.svc

Copy the file, make any desired changes (see the options below) and apply:

$ kubectl apply -f deploy/linstor-scheduler.yaml
configmap/linstor-scheduler created
deployment.apps/linstor-scheduler created
serviceaccount/linstor-scheduler created
clusterrole.rbac.authorization.k8s.io/linstor-scheduler created
role.rbac.authorization.k8s.io/linstor-scheduler created
clusterrolebinding.rbac.authorization.k8s.io/linstor-scheduler created
rolebinding.rbac.authorization.k8s.io/linstor-scheduler created

$ kubectl -n kube-system get pods -l app.kubernetes.io/name=linstor-scheduler
NAME                                 READY   STATUS    RESTARTS   AGE
linstor-scheduler-6bb88fc66c-bq4fm   2/2     Running   0          52s
linstor-scheduler-6bb88fc66c-tllgm   2/2     Running   0          52s

Usage

To make your applications using linstor-scheduler, use the schedulerName: linstor field. For example, Pod Templates in a StatefulSet should look like:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: my-stateful-app
spec:
  serviceName: my-stateful-app
  selector:
    matchLabels:
      app.kubernetes.io/name: my-stateful-app
  template:
    metadata:
      labels:
        app.kubernetes.io/name: my-stateful-app
    spec:
      schedulerName: linstor
    ...

Configuration

linstor-scheduler-extender uses the environment variables specified in the golinstor library for configuration.

Variable	Description
LS_CONTROLLERS	A comma-separated list of LINSTOR controller URLs to connect to.
LS_USERNAME	Username to use for HTTP basic auth.
LS_PASSWORD	Password to use for HTTP basic auth.
LS_ROOT_CA	CA certificate to use for authenticating the server.
LS_USER_KEY	TLS key to use for authenticating the client to the server.
LS_USER_CERTIFICATE	TLS certificate to use for authenticating the client to the server.

The linstor-scheduler-extender itself can be configured using the following flags:

--verbose      Enable verbose logging

Admission controller

In case you want to automatically assign shcedulerName to all pods that use linstor volumes, you can enable admission controller, check out the single file deployment

The deployment will create:

• All needed RBAC resources
• A Deployment spawning 2 replicas of linstor-scheduler-admission
• A mutating admission webhook configuration for all pods in a cluster
• Two jobs for generate certificates and inject ca into webhook configuration

$ kubectl apply -f deploy/linstor-scheduler-admission.yaml
serviceaccount/linstor-scheduler-admission created
rolebinding.rbac.authorization.k8s.io/linstor-scheduler-admission created
clusterrolebinding.rbac.authorization.k8s.io/linstor-scheduler-admission created
role.rbac.authorization.k8s.io/linstor-scheduler-admission created
clusterrole.rbac.authorization.k8s.io/linstor-scheduler-admission created
job.batch/linstor-scheduler-admission-create created
job.batch/linstor-scheduler-admission-patch created
deployment.apps/linstor-scheduler-admission created
service/linstor-scheduler-admission created
mutatingwebhookconfiguration.admissionregistration.k8s.io/linstor-scheduler.admission.linbit.com created

$ kubectl -n kube-system get pods -l app.kubernetes.io/name=linstor-scheduler-admission
linstor-scheduler-admission-7d44d895c8-gmqc5   1/1     Running       0                24s
linstor-scheduler-admission-7d44d895c8-j99r6   1/1     Running       0                24s

The linstor-scheduler-admission itself can be configured using the following flags:

-driver string
  	Driver name (default "linstor.csi.linbit.com")
-scheduler string
  	Scheduler name (default "linstor")
-tls-cert-file string
  	TLS certificate file
-tls-key-file string
  	TLS key file