Chapter 5. Red Hat Operators

Purpose

The Cloud Credential Operator manages cloud provider credentials as Kubernetes custom resource definitions (CRDs).

Project

openshift-cloud-credential-operator

CRDs

Configuration objects

No configuration required.

Notes

Purpose

The Cluster Authentication Operator installs and maintains the Authentication custom resource in a cluster and can be viewed with:

$ oc get clusteroperator authentication -o yaml

Project

cluster-authentication-operator

Purpose

The Cluster Autoscaler Operator manages deployments of the OpenShift Cluster Autoscaler using the cluster-api provider.

Project

cluster-autoscaler-operator

CRDs

Purpose

The Cluster Image Registry Operator manages a singleton instance of the OpenShift Container Platform registry. It manages all configuration of the registry, including creating storage.

On initial start up, the Operator creates a default image-registry resource instance based on the configuration detected in the cluster. This indicates what cloud storage type to use based on the cloud provider.

If insufficient information is available to define a complete image-registry resource, then an incomplete resource is defined and the Operator updates the resource status with information about what is missing.

The Cluster Image Registry Operator runs in the openshift-image-registry namespace and it also manages the registry instance in that location. All configuration and workload resources for the registry reside in that namespace.

Project

cluster-image-registry-operator

Purpose

The Cluster Monitoring Operator manages and updates the Prometheus-based cluster monitoring stack deployed on top of OpenShift Container Platform.

Project

openshift-monitoring

CRDs

Configuration objects

$ oc -n openshift-monitoring edit cm cluster-monitoring-config

Purpose

The Cluster Network Operator installs and upgrades the networking components on an OpenShift Container Platform cluster.

Purpose

The OpenShift Controller Manager Operator installs and maintains the OpenShiftControllerManager custom resource in a cluster and can be viewed with:

$ oc get clusteroperator openshift-controller-manager -o yaml

The custom resource definition (CRD) openshiftcontrollermanagers.operator.openshift.io can be viewed in a cluster with:

$ oc get crd openshiftcontrollermanagers.operator.openshift.io -o yaml

Project

cluster-openshift-controller-manager-operator

Purpose

The Cluster Samples Operator manages the sample image streams and templates stored in the openshift namespace.

On initial start up, the Operator creates the default samples configuration resource to initiate the creation of the image streams and templates. The configuration object is a cluster scoped object with the key cluster and type configs.samples.

The image streams are the Red Hat Enterprise Linux CoreOS (RHCOS)-based OpenShift Container Platform image streams pointing to images on registry.redhat.io. Similarly, the templates are those categorized as OpenShift Container Platform templates.

The Cluster Samples Operator deployment is contained within the openshift-cluster-samples-operator namespace. On start up, the install pull secret is used by the image stream import logic in the internal registry and API server to authenticate with registry.redhat.io. An administrator can create any additional secrets in the openshift namespace if they change the registry used for the sample image streams. If created, those secrets contain the content of a config.json for docker needed to facilitate image import.

The image for the Cluster Samples Operator contains image stream and template definitions for the associated OpenShift Container Platform release. After the Cluster Samples Operator creates a sample, it adds an annotation that denotes the OpenShift Container Platform version that it is compatible with. The Operator uses this annotation to ensure that each sample matches the compatible release version. Samples outside of its inventory are ignored, as are skipped samples.

Modifications to any samples that are managed by the Operator are allowed as long as the version annotation is not modified or deleted. However, on an upgrade, as the version annotation will change, those modifications can get replaced as the sample will be updated with the newer version. The Jenkins images are part of the image payload from the installation and are tagged into the image streams directly.

The samples resource includes a finalizer, which cleans up the following upon its deletion:

Upon deletion of the samples resource, the Cluster Samples Operator recreates the resource using the default configuration.

Project

cluster-samples-operator

Purpose

The Cluster Storage Operator sets OpenShift Container Platform cluster-wide storage defaults. It ensures a default storage class exists for OpenShift Container Platform clusters.

Project

cluster-storage-operator

Configuration

No configuration is required.

Notes

Purpose

Project

cluster-version-operator

Purpose

The Console Operator installs and maintains the OpenShift Container Platform web console on a cluster.

Project

console-operator

Purpose

The DNS Operator deploys and manages CoreDNS to provide a name resolution service to pods that enables DNS-based Kubernetes Service discovery in OpenShift Container Platform.

The Operator creates a working default deployment based on the cluster’s configuration.

The DNS Operator manages CoreDNS as a Kubernetes daemon set exposed as a service with a static IP. CoreDNS runs on all nodes in the cluster.

Project

cluster-dns-operator

Purpose

The etcd cluster Operator automates etcd cluster scaling, enables etcd monitoring and metrics, and simplifies disaster recovery procedures.

Project

cluster-etcd-operator

CRDs

Configuration objects

$ oc edit etcd cluster

Purpose

The Ingress Operator configures and manages the OpenShift Container Platform router.

Project

openshift-ingress-operator

CRDs

Configuration objects

Notes

The Ingress Operator sets up the router in the openshift-ingress project and creates the deployment for the router:

$ oc get deployment -n openshift-ingress

The Ingress Operator uses the clusterNetwork[].cidr from the network/cluster status to determine what mode (IPv4, IPv6, or dual stack) the managed ingress controller (router) should operate in. For example, if clusterNetwork contains only a v6 cidr, then the ingress controller operate in IPv6-only mode.

In the following example, ingress controllers managed by the Ingress Operator will run in IPv4-only mode because only one cluster network exists and the network is an IPv4 cidr:

$ oc get network/cluster -o jsonpath='{.status.clusterNetwork[*]}'

map[cidr:10.128.0.0/14 hostPrefix:23]

Purpose

The Kubernetes API Server Operator manages and updates the Kubernetes API server deployed on top of OpenShift Container Platform. The Operator is based on the OpenShift library-go framework and it is installed using the Cluster Version Operator (CVO).

Project

openshift-kube-apiserver-operator

CRDs

Configuration objects

$ oc edit kubeapiserver

Purpose

The Kubernetes Controller Manager Operator manages and updates the Kubernetes Controller Manager deployed on top of OpenShift Container Platform. The Operator is based on OpenShift library-go framework and it is installed via the Cluster Version Operator (CVO).

It contains the following components:

By default, the Operator exposes Prometheus metrics through the metrics service.

Project

cluster-kube-controller-manager-operator

Purpose

The Kubernetes Scheduler Operator manages and updates the Kubernetes Scheduler deployed on top of OpenShift Container Platform. The Operator is based on the OpenShift Container Platform library-go framework and it is installed with the Cluster Version Operator (CVO).

The Kubernetes Scheduler Operator contains the following components:

By default, the Operator exposes Prometheus metrics through the metrics service.

Project

cluster-kube-scheduler-operator

Configuration

The configuration for the Kubernetes Scheduler is the result of merging:

All of these are sparse configurations, invalidated JSON snippets which are merged in order to form a valid configuration at the end.

Purpose

The Machine API Operator manages the lifecycle of specific purpose custom resource definitions (CRD), controllers, and RBAC objects that extend the Kubernetes API. This declares the desired state of machines in a cluster.

Project

machine-api-operator

CRDs

Purpose

The Machine Config Operator manages and applies configuration and updates of the base operating system and container runtime, including everything between the kernel and kubelet.

There are four components:

Project

openshift-machine-config-operator

Purpose

The Marketplace Operator is a conduit to bring off-cluster Operators to your cluster.

Project

operator-marketplace

Purpose

The Node Tuning Operator helps you manage node-level tuning by orchestrating the Tuned daemon. The majority of high-performance applications require some level of kernel tuning. The Node Tuning Operator provides a unified management interface to users of node-level sysctls and more flexibility to add custom tuning specified by user needs.

The Operator manages the containerized Tuned daemon for OpenShift Container Platform as a Kubernetes daemon set. It ensures the custom tuning specification is passed to all containerized Tuned daemons running in the cluster in the format that the daemons understand. The daemons run on all nodes in the cluster, one per node.

Node-level settings applied by the containerized Tuned daemon are rolled back on an event that triggers a profile change or when the containerized Tuned daemon is terminated gracefully by receiving and handling a termination signal.

The Node Tuning Operator is part of a standard OpenShift Container Platform installation in version 4.1 and later.

Project

cluster-node-tuning-operator

Purpose

Operator Lifecycle Manager (OLM) helps users install, update, and manage the lifecycle of Kubernetes native applications (Operators) and their associated services running across their OpenShift Container Platform clusters. It is part of the Operator Framework, an open source toolkit designed to manage Operators in an effective, automated, and scalable way.

Figure 5.1. Operator Lifecycle Manager workflow

OLM runs by default in OpenShift Container Platform 4.5, which aids cluster administrators in installing, upgrading, and granting access to Operators running on their cluster. The OpenShift Container Platform web console provides management screens for cluster administrators to install Operators, as well as grant specific projects access to use the catalog of Operators available on the cluster.

For developers, a self-service experience allows provisioning and configuring instances of databases, monitoring, and big data services without having to be subject matter experts, because the Operator has that knowledge baked into it.

CRDs

Operator Lifecycle Manager (OLM) is composed of two Operators: the OLM Operator and the Catalog Operator.

Each of these Operators is responsible for managing the custom resource definitions (CRDs) that are the basis for the OLM framework:

Each of these Operators is also responsible for creating the following resources:

OLM Operator

The OLM Operator is responsible for deploying applications defined by CSV resources after the required resources specified in the CSV are present in the cluster.

The OLM Operator is not concerned with the creation of the required resources; you can choose to manually create these resources using the CLI or using the Catalog Operator. This separation of concern allows users incremental buy-in in terms of how much of the OLM framework they choose to leverage for their application.

The OLM Operator uses the following workflow:

Catalog Operator

The Catalog Operator is responsible for resolving and installing cluster service versions (CSVs) and the required resources they specify. It is also responsible for watching catalog sources for updates to packages in channels and upgrading them, automatically if desired, to the latest available versions.

To track a package in a channel, you can create a Subscription object configuring the desired package, channel, and the CatalogSource object you want to use for pulling updates. When updates are found, an appropriate InstallPlan object is written into the namespace on behalf of the user.

The Catalog Operator uses the following workflow:

Catalog Registry

The Catalog Registry stores CSVs and CRDs for creation in a cluster and stores metadata about packages and channels.

A package manifest is an entry in the Catalog Registry that associates a package identity with sets of CSVs. Within a package, channels point to a particular CSV. Because CSVs explicitly reference the CSV that they replace, a package manifest provides the Catalog Operator with all of the information that is required to update a CSV to the latest version in a channel, stepping through each intermediate version.

Additional resources

For more information, see the sections on understanding Operator Lifecycle Manager (OLM).

Purpose

The OpenShift API Server Operator installs and maintains the openshift-apiserver on a cluster.

Project

openshift-apiserver-operator

CRDs

Purpose

The Prometheus Operator for Kubernetes provides easy monitoring definitions for Kubernetes services and deployment and management of Prometheus instances.

Once installed, the Prometheus Operator provides the following features:

Project

prometheus-operator