Composite resource

As explained in Platform Engineering on Kubernetes

A Crossplane composite resource is a higher-level Kubernetes API resource that represents a composed infrastructure capability backed by underlying managed resources.

A Crossplane composite resource (XR) is a Kubernetes API resource that gives application teams a simplified interface for requesting a composed infrastructure capability. Platform teams define which underlying resources and cloud-provider configurations satisfy that request. section 5.2.2

The abstraction hides implementation choices such as whether a PostgreSQL request becomes a Google Cloud SQL instance, network configuration, and bucket. Crossplane compositions create those resources and can publish connection details in Kubernetes Secrets. section 5.2.2

A composite-resource workflow separates platform responsibilities from application delivery:

• Platform teams define Composite Resource Definitions and compositions that wire together managed resources for a cloud provider. section 5.2.2
• Application teams request domain-specific resources through the Kubernetes API without selecting the provider or every underlying component. section 5.2.2
• Crossplane provisions the composed resources, reports synchronization and readiness, and creates credentials for workloads to consume. section 5.2.3 section 5.3.1

Conference application infrastructure

A Conference deployment requests database and message-broker composite resources. Kubernetes output shows SQL, key-value, and Kafka resources with SYNCED and READY set to True; generated Secrets and service endpoints then supply application connection settings. section 5.3.1

Figure 5.7 Provisioning a PostgreSQL instance in Google Cloud with Crossplane compositions

Trace how a PostgreSQL composite resource expands into Google Cloud infrastructure and supporting configuration. section 5.2.2

How Platform Engineering on Kubernetes covers it

How deep it goes

Explains composition boundaries, provisioning prerequisites, readiness status, and generated credentials without detailing composition schemas.

Examples

Uses PostgreSQL, Redis, and Kafka resources, with kubectl output showing readiness, services, and generated credentials.

What it assumes

Assumes a Kubernetes cluster, Crossplane installation, provider configuration, cloud APIs, and sufficient provider permissions.

What you can do after

Apply it via the Kubernetes API to request composed infrastructure and connect workloads through generated Secrets and service endpoints.

How it connects

Connects Composite Resource Definitions, Crossplane compositions, managed resources, Kubernetes Secrets, and cloud providers.

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Related concepts

• Crossplane compositionuses · A Crossplane composition is a declarative Crossplane pattern that combines multiple managed resources and configuration into a higher-level infrastructure resource.
• managed resourceuses · A managed resource is a Kubernetes resource whose desired state and lifecycle are reconciled with a corresponding external infrastructure resource by a Crossplane provider.

This explainer was generated by Manning's knowledge graph from the text of Platform Engineering on Kubernetes. The section links point to the parts of the book it draws on.