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modules/abstraction-layers.adoc

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[id='abstraction-layers-{context}']
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= {product-title} abstraction layers
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The Docker service provides the abstraction for packaging and creating
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The container service provides the abstraction for packaging and creating
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Linux-based, lightweight container images. Kubernetes provides the
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cluster management and orchestrates containers on multiple hosts.
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modules/architecture-overview.adoc

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{product-title} v4 runs on top of a Kubernetes cluster, with data about the
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objects stored in etcd, a reliable clustered key-value store. The cluster is
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enhanced with standard components that you need to run your cluster, including
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network, ingress, logging and monitoring, that run as Operators to increase the
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network, ingress, logging, and monitoring, that run as Operators to increase the
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ease and automation of installation, scaling, and maintenance.
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////

modules/cloud_installations.adoc

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When you install a fully-managed {product-title} cluster, you download the
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installer from link:try.openshift.com. This site manages:
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* Rest API for accounts
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* REST API for accounts
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* Registry tokens, which are the pull secrets that you use to obtain the required
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components
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* Cluster registration, which associates the cluster identity to your Red Hat
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account to facilitate usage metrics gathering
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account to facilitate the gathering of usage metrics
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In {product-title} version 4.0, the installer is a go binary that performs a
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In {product-title} version 4.0, the installer is a Go binary that performs a
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series of file transformations on a set of assets. With the fully-managed option,
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you delegate the infrastructure bootstrapping and provisioning to the installer
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instead of doing it yourself. Because you do not use the installer to upgrade or

modules/installation-options.adoc

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You must provide the hosts and update RHEL on them. {product-title} provides:
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* Managed control plane
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* Ansible to manage kubelet and runtime
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* Ansible to manage kubelet and container runtime
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With both installation types, installation and upgrade both use an Operator

modules/machine-api-overview.adoc

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The three primary resources are:
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`Machines`:: A fundamental unit that describes a node host. A `machine` has a
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`Machines`:: A fundamental unit that describes a `Node`. A `machine` has a
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class, which describes the types of compute nodes that are offered for different
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cloud platforms. For example, a `machine` type for a worker node on Amazon Web
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Services (AWS) might define a specific machine type and required metadata.
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`MachineAutoscaler`:: This resource automatically scales `machines` in
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a cloud. You can set the minimum and maximum scaling boundaries for nodes in a
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specified `MachineSet`, and the `MachineAutoscaler` maintains that range of nodes.
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The `MachineAutoscaler` object takes effect after a `ClusterAutoscaler` object
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exists. Both `ClusterAutoscaler` and `MachineAutoscaler` resources are made
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available by the `ClusterAutoscalerOperator`.
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`MachineHealthChecker`:: This resource detects when a machine is unhealthy,
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deletes it, and, on supported platforms, makes a new machine.
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`ClusterAutoscaler`:: This resource is based on the upstream
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ScalingPolicy so you can scale up nodes but not scale them down.
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In 3.x, you couldn't roll out a multi-az architecture easily because the cluster
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did not manage machine provisioning. It's easier in 4.0. Each machinset is scoped
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to a single az so the installer will actually send out machinesets across AZs
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on your behalf. And then because your compute is actually dynamic here, and in
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In {product-title} version 3.11, you could not roll out a multi-zone architecture easily because the cluster
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did not manage machine provisioning. It is easier in 4.0. Each `MachineSet` is scoped
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to a single zone, so the installer sends out `MachineSets` across availability zones
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on your behalf. And then because your compute is dynamic, and in
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the face of a zone failure, you always have a zone for when you need to rebalance
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your machines. the autoscaler proviedes best-effort balancing over the life of a cluster.
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your machines. The autoscaler provides best-effort balancing over the life of a cluster.

modules/node-management.adoc

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The fully-managed version of {product-title} version 4.0 integrates management of
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the container operating system and cluster management. Because the cluster manages
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both its updates and updates to RHCOS, {product-title} provides an opinionated
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lifecycle management experience that simplifies the orchestration of node upgrades.
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lifecycle management experience that simplifies the orchestration of upgrades.
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{product-title} employs three DaemonSets and controllers to simplify node management:
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DaemonSet runs on each compute node in the cluster and watches for changes in
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the machine configuration for it to apply. The machine configuration is a subset
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of the Ignition configuration. The `machine-config-daemon` reads the machine configuration to see
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if it needs to do an `os tree` update, if it should apply a series of `systemd`
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if it needs to do an OSTree update, if it should apply a series of systemd
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kubelet file changes, configuration changes, or other changes to the
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operating system or {product-title} configuration.
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pods, applies the update, and reboots. This process is key to the success of
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managing {product-title} and RHCOS updates together.
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The `machine-config-server` applies configurations to nodes as they join the
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The `machine-config-server` provides configurations to nodes as they join the
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cluster. It orchestrates configuration to nodes and changes to the operating system
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and is used in both cluster installation and node maintenance. The
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`machine-config-server` components upgrade the operating system and controls the Ignition
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configuration for nodes.
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////
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The `bootkube` process calls the `machine-config-server` component when the
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{product-title} installer bootstraps the initial master node. After installation,
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the `machine-config-server` runs in the cluster. It reads the `machine-config`
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custom resource definitions (CRDs) and serves the required Ignition configurations
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to new nodes when they join the cluster.
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////

modules/node-types.adoc

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[id='node-roles-{context}']
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= Node roles in {product-title}
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{product-title} assigns nodes different roles. These roles define the function
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{product-title} assigns hosts different roles. These roles define the function
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of the node within the cluster. The cluster contains standard definitions for
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standard role types, such as bootstrap, master, and worker.
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modules/operators-overview.adoc

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In {product-title} v4, all control plane components are run and managed as
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applications on the infrastructure to ensure a uniform and consistent management
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experience. The control plane, services run as static pods so they can
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experience. The control plane services run as static pods so they can
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manage normal workloads or processes the same way that they manage disaster
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recovery. Aside from the core control plane components, other services run as
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normal pods on the cluster, managed by regular Kubernetes constructs. Unlike in the past
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The cluster version Operator, when we talk about payload manifests, is a
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second-level Operator, the Operators that actually manage {product-title} as if
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it were a native Kubernetes application. Second-level Operators are not a
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codified concept, but thenamespace where your code exists, the service accounts
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or roles the second-level Operator runs as, the CRD and pull secret that drives
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the operation of the Operator, and the Operator deployment.
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codified concept, but the namespace where your code exists, the service accounts
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or roles the second-level Operator runs as, the
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link:https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/#customresourcedefinitions[Custom Resource Definition] (CRD)
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and pull secret that drives the operation of the Operator, and the Operator deployment.
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Second-level Operators write out to a CRD resource called the cluster Operator
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Second-level Operators write out to a CRD resource called the ClusterOperator
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that allows the cluster version Operator to understand the progress of the
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managed component's deployment
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managed component's deployment.
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[id='OLM-operators-{context}']
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== Operators managed by OLM
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In addition to the Operators that comprise {product-title}, the Cluster
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Operator Lifecycle Management (OLM) component manages more Operators.
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The Cluster Operator Lifecycle Management (OLM) component manages Operators
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that are available for use in applications. It does not manage the Operators that
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comprise {product-title}.
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OLM is a framework that manages Kubernetes-native applications as Operators.
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Instead of managing Kubernetes manifests, it manages Kubernetes Operators.
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OLM manages two classes of Operators, Red Hat Operators and certified Operators.
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Some Red Hat Operators drive the cluster functions, like the scheduler and
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problem detectors. Others are provider for you to manage yourself and use in
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problem detectors. Others are provided for you to manage yourself and use in
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your applications, like etcd. {product-title} also offers certified Operators,
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which the community built around the OLM and maintains. These certified Operators
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are traditional applications that are Kubernetes-aware because they are wrapped
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in an Operator.
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which the community built and maintains. These certified Operators provide an
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API layer to traditional applications so you can manage the application through
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Kubernetes constructs.

modules/update-service-overview.adoc

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The {product-title} update service is the hosted service that provides over the air updates to both
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{product-title} and RHCOS. It provides a graph, or diagram that contain
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_vertices_ and the _edges_ that connect them, of component Operators. The edges
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in the graph show which versions you can safely upgrade to. The cluster version
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Operator checks with the {product-title} update service and determines valid upgrades and upgrade paths
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in the graph show which versions you can safely upgrade to, and the vertices
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vertices are update payloads that specify the intended state of the managed cluster components.
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The cluster versionOperator checks with the {product-title} update service and determines valid upgrades and upgrade paths
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based on current component versions and information in the graph. If you
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configure it to do so, the {product-title} update service sends the release artifacts that it needs to
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perform the upgrade to your image registry, and the cluster version Operator
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release, the {product-title} update service can apply the update to your cluster or notify you that it
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////
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The interaction between the registry and the {product-title} update service is different during
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bootstrap and continuous update modes. When you bootstrap the initial
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infrastructure, the cluster version Operator finds
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the fully qualified image name for the shortname of the images that it needs to
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apply to the server during installation. It looks at the image stream that it needs
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to apply and renders it to disk. It calls bootkube and waits for a temporary minimal control
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plane to come up and load the cluster version Operator.
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////
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During continuous update mode, two controllers run. One continuously updates
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the payload manifests, applies them to the cluster, and outputs the status of
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the controlled rollout of the Operators, whether they are available, upgrading,
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or failed. The second controller constantly checks with to Cincinnati to
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or failed. The second controller polls the {product-title} update service to
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determine if updates are available.

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