FROM <source-image> ADD <path-to-binary> /usr/local/bin/kube-scheduler
You can run multiple, custom schedulers alongside the default scheduler and configure which scheduler to use for each pods.
To schedule a given pod using a specific scheduler, specify the name of the scheduler in that pod specification.
Information on how to create the scheduler binary is outside the scope of this document. For an example, see Configure Multiple Schedulers in the Kubernetes documentation. |
The general process for including a custom scheduler in your cluster involves creating an image and including that image in a deployment.
Package your scheduler binary into a container image.
Create a container image containing the scheduler binary.
For example:
FROM <source-image> ADD <path-to-binary> /usr/local/bin/kube-scheduler
Save the file as Dockerfile, build the image, and push it to a registry.
For example:
docker build -t <dest_env_registry_ip>:<port>/<namespace>/<image name>:<tag> docker push <dest_env_registry_ip>:<port>/<namespace>/<image name>:<tag>
In OpenShift Container Platform, create a deployment for the custom scheduler.
apiVersion: v1
kind: ServiceAccount
metadata:
name: custom-scheduler
namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: custom-scheduler
subjects:
- kind: ServiceAccount
name: custom-scheduler
namespace: kube-system
roleRef:
kind: ClusterRole
name: system:kube-scheduler
apiGroup: rbac.authorization.k8s.io
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: custom-scheduler
namespace: kube-system
labels:
app: custom-scheduler
spec:
replicas: 1
selector:
matchLabels:
app: custom-scheduler
template:
metadata:
labels:
app: custom-scheduler
spec:
serviceAccount: custom-scheduler
containers:
- name: custom-scheduler
image: "<namespace>/<image name>:<tag>" (1)
imagePullPolicy: Always
1 | Specify the container image you created for the custom scheduler. |
After your custom scheduler is deployed in your cluster, you can configure pods to use that scheduler instead of the default scheduler.
Create or edit a pod configuration and specify the name of the scheduler with the schedulerName
parameter. The name must be unique.
apiVersion: v1
kind: Pod
metadata:
name: custom-scheduler-example
labels:
name: custom-scheduler-example
spec:
schedulerName: custom-scheduler (1)
containers:
- name: pod-with-second-annotation-container
image: docker.io/ocpqe/hello-pod
1 | The name of the scheduler to use. When no scheduler name is supplied, the pod is automatically scheduled using the default scheduler. |
Run the following command to create the pod:
$ oc create -f <file-name>.yaml
For example:
$ oc create -f custom-scheduler-example.yaml
Run the following command to check that the pod was created:
$ oc get pod <file-name>
For example:
$ oc get pod custom-scheduler-example
NAME READY STATUS RESTARTS AGE
custom-scheduler-example 1/1 Running 0 4m
Run the following command to check that the custom scheduler scheduled the pod:
$ oc describe pod <pod-name>
For example:
$ oc describe pod custom-scheduler-example
The name of the scheduler is listed, as shown in the following truncated output:
... Events: FirstSeen LastSeen Count From SubObjectPath Type Reason Message --------- -------- ----- ---- ------------- -------- ------ ------- 1m 1m 1 custom-scheduler Normal Scheduled Successfully assigned custom-scheduler to <$node1> ...