Technology articles

Depending on your workloads, you may want to have workers with realtime kernel in your cluster. How to configure and how to enroll the nodes into an Openshift cluster is not on the scope of this article, we will assume that you have the worker node up and running with realtime kernel. Once you have it, how to properly schedule workloads that make use of it? CPU manager and kubelet static policy - https://docs.openshift.com/container-platform/4.2/scalability_and_performance/using-cpu-manager.html CPU Manager manages groups of CPUs and constrains workloads to specific CPUs. This is useful for several cases, in our case for low-latency applications. In order to enable CPU manager following steps are needed: Label a node with cpu manager: # oc label node perf-node.example.com cpumanager=true Edit the machineconfigpool worker, and add a label to reference a custom kubelet: # oc edit machineconfigpool worker metadata: creationTimestamp: 2019-xx-xxx generation: 3 labels: ...

This blogpost is going to show how to automatically enroll RHEL 8 (realtime) to Openshift 4.1 deployments, using UPI method. This assumes that you will setup an OpenShift cluster using UPI, following the according documentation: https://docs.openshift.com/container-platform/4.1/installing/installing_bare_metal The procedure on how to spin up this cluster in a semi-automated way is also shown at https://github.com/redhat-nfvpe/upi-rt . This article will assume that you have this UPI cluster up and running. Enroll RHEL 8 nodes as workers By default, all nodes added into an OpenShift cluster are based on RHCOS. But there are use caes where you may need RHEL nodes. This is the case of RT (real time) nodes, where you need an specific kernel. This can be achieved with the help of kickstart, and some specific configuration of PXE kernel args (in this case achieved with matchbox). We are going to use RHEL8 images, booted with PXE, but we are going to add some specific configuration to...