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poor-mans-drs

A Red Hat Advanced Cluster Management(ACM) Policy that migrates VM's from nodes that have high cpu and memory usage.

How does it do this:
- ACM will loop through every worker node and get their allocatable CPU/Memory
- ACM will loop through every worker node and get their current CPU/Memory Usage
- ACM policy sets a value for usage % to start migrating nodes, default is set to 50%. Value can be changed in policy.
- ACM will create a configmap called drs-worker-node-name-info on openshift-cnv with the values obtained and calculated from above.
- ACM will loop through virtual machines and compare the status of the nodes they are running on with the values calculated above.
- If node VM is on has high memory and cpu usage, ACM will highlight VM for migration. - ACM will check if their is an existing migration for that VM that is not Failed or Succeded status i.e A running Migration. If there is nor running migration ACM will create a new VM Migration object to move the VM.

Tested On

  • OCP 4.15
  • ACM 2.11

Deployment steps

  • Install ACM

  • Install OpenShift Virtualization

  • Steps must be run with cluster-admin privileges

  • Steps might require subscription-admin privilege

    oc adm policy add-cluster-role-to-user open-cluster-management:subscription-admin $(oc whoami)

  • Create Sample Deployment artifacts

    oc apply -k ./deploy

  • To exclude a VM from being managed by this policy label the VM with "acm-drs/exclude"

  • In the ACM UI , under infrastructure, clustersets,drs clusterset - add the clusters that should be inside the drs clusterset.

  • You can run one of the below test scenarios

    Test1:
    Running a stress-ng test pod that moves with the VM. Script below will get VM node and apply a node selector for the same node to the stress-ng pod.The stress-ng pod will stress the node CPU which should trigger the ACM policy to create a VM Migration to move the VM to another node. After a small wait the process should start all over again.

    • Start test and create Infra
    ./test/test1/test1.sh start
    • Exit from Test- CTRL-C from previous command and run below
    ./test/test1/test1.sh stop

    Test1 Verification:

    • Once test starts you should see increased load on the stressed node.

    • You can confirm from the configmap created by the policy for tracking metrics. Will be the same as the node on openshift-cnv namespace. Node-metrics-configmap

    • Script logs will also tell the source and target VM's for Node migrations. Script Logs

    • You can also list the VMIM objects to see the migrations. VMIM Objects