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openshift-docs/modules/cluster-api-architecture.adoc
2022-10-21 13:19:18 +00:00

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// Module included in the following assemblies:
//
// * machine_management/capi-machine-management.adoc
:_content-type: CONCEPT
[id="cluster-api-architecture_{context}"]
= Cluster API architecture
The {product-title} integration of the upstream Cluster API is implemented and managed by the Cluster CAPI Operator. The Cluster CAPI Operator and its operands are provisioned in the `openshift-cluster-api` namespace, in contrast to the Machine API, which uses the `openshift-machine-api` namespace.
[id="capi-arch-operator"]
== The Cluster CAPI Operator
The Cluster CAPI Operator is an {product-title} Operator that maintains the lifecycle of Cluster API resources. This Operator is responsible for all administrative tasks related to deploying the Cluster API project within an {product-title} cluster.
If a cluster is configured correctly to allow the use of the Cluster API, the Cluster CAPI Operator installs the Cluster API Operator on the cluster.
[NOTE]
====
The Cluster CAPI Operator is distinct from the upstream Cluster API Operator.
====
For more information, see the entry for the Cluster CAPI Operator in the _Cluster Operators reference_ content.
[id="capi-arch-resources"]
== Primary resources
The Cluster API is comprised of the following primary resources. For the Technology Preview of this feature, you must create these resources manually in the `openshift-cluster-api` namespace.
Cluster:: A fundamental unit that represents a cluster that is managed by the Cluster API.
Infrastructure:: A provider-specific resource that defines properties that are shared by all the compute machine sets in the cluster, such as the region and subnets.
Machine template:: A provider-specific template that defines the properties of the machines that a compute machine set creates.
Machine set:: A group of machines.
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Compute machine sets are to machines as replica sets are to pods. If you need more machines or must scale them down, you change the `replicas` field on the compute machine set to meet your compute needs.
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With the Cluster API, a compute machine set references a `Cluster` object and a provider-specific machine template.
Machine:: A fundamental unit that describes the host for a node.
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The Cluster API creates machines based on the configuration in the machine template.