Deploying Applications to Multiple Clusters with Dynamic Scheduling

Scheduling applications of multiple replicas to several clusters by cluster capacity

This tutorial will walk you through how to deploy applications to multiple clusters with dynamic scheduling. It is different from static dividing scheduling. When using dynamic scheduling, the replicas of an application will be split based on cluster capacity.

Defining Your Applications

Let’s see an example using dynamic scheduling. Below Subscription “dynamic-dividing-scheduling-demo” defines the target child clusters to be distributed to, and the resources to be deployed with.

# examples/dynamic-dividing-scheduling/subscription.yaml
apiVersion: apps.clusternet.io/v1alpha1
kind: Subscription
metadata:
  name: dynamic-dividing-scheduling-demo
  namespace: default
spec:
  subscribers: # filter out a set of desired clusters
    - clusterAffinity:
        matchExpressions:
          - key: clusters.clusternet.io/cluster-id
            operator: Exists
  schedulingStrategy: Dividing
  dividingScheduling:
    type: Dynamic
    dynamicDividing:
      strategy: Spread # currently we only support Spread dividing strategy
  feeds: # defines all the resources to be deployed with
    - apiVersion: v1
      kind: Namespace
      name: qux
    - apiVersion: v1
      kind: Service
      name: my-nginx-svc
      namespace: qux
    - apiVersion: apps/v1 # with a total of 6 replicas
      kind: Deployment
      name: my-nginx
      namespace: qux

The Deployment qux/my-nginx above will run in a set of clusters with a total of 6 replicas. For example, if we’ve got three matching clusters as below.

  • cluster-01 can run 3 replicas of Deployment qux/my-nginx
  • cluster-02 can run 6 replicas of Deployment qux/my-nginx
  • cluster-03 can run 9 replicas of Deployment qux/my-nginx

clusternet-scheduler will assign replicas to each matching cluster by their capacity. As a result, these three clusters will run 1, 2, 3 replicas respectively.

You can get the scheduling result by checking the status of Subscription dynamic-dividing-scheduling-demo.

bindingClusters:
  - clusternet-v7wzq/clusternet-cluster-bb2xp
  - clusternet-wlf5b/clusternet-cluster-skxd4
  - clusternet-bbf20/clusternet-cluster-aqx3b
  desiredReleases: 6
  replicas:
    apps/v1/Deployment/qux/my-nginx:
    - 1
    - 2
    - 3
    v1/Namespace/qux: []
    v1/Service/qux/my-nginx-svc: []

If you want to apply overrides per cluster, please follow How to Set Overrides in Clusternet.

Applying Your Applications

After installing kubectl plugin kubectl-clusternet, you could run commands below to distribute this application to child clusters.

$ kubectl clusternet apply -f examples/dynamic-dividing-scheduling/
namespace/qux created
deployment.apps/my-nginx created
service/my-nginx-svc created
subscription.apps.clusternet.io/dynamic-dividing-scheduling-demo created
$ # or
$ # kubectl-clusternet apply -f examples/dynamic-dividing-scheduling/

You can check aggregated status of feeds/resources running in each child clusters.


Last modified July 14, 2022: add docs on dynamic scheduling and status aggregation (#26) (588d770)