function-generate-subnets

A Crossplane Composition Function which will generate an ObserveOnly subnet object for each subnet ID found in an EKS cluster resource, then patch specific information from those objects to a field on the composite resource.

In order to use this function as part of the Composition, the composition must be written to use pipeline mode. See the documentation on Composition functions to better understand how this is integrated

Composition integration

This function is placed in the pipeline with a reference to the cluster object for that composition and an additional reference of where to patch information about the subnets it is generating for that provider.

This should be specified in your composition as:

  - step: generate-subnets
    functionRef:
      name: function-generate-subnets
    input:
      apiVersion: generatesubnets.fn.giantswarm.io
      kind: Subnet
      metadata:
        namespace: crossplane
      spec:
        clusterRef: eks-cluster
        patchTo: status.subnets

The function requires information from the XR and is opinionated about how that information should be presented.

In order to support the integration of this function into your pipelines, details about the XR requirements are published in definition_xrs.yaml.

The relevant sections of this XR specification should be extracted and merged into the definition you are writing. The specification cannot be used independantly as an XRD as it does not define all the required elements of an XRD, just the custom fields required by this function.

How it works

This function reads the subnet IDs from a cluster object relevant to the cloud provider.

For each integrated type, only the official upbound providers are supported.

It then uses the subnet IDs to generate one Subnet object for each subnet in the list and adds these to the set of desired composed objects and allows them to reconcile.

Once reconciliation is complete, the function collects information from the status.atProvider for each subnet and compiles this into a list of objects which is then applied to the status field of the XR.

As part of the reconciliation, the function calls out to the cloud provider to retrieve additional information such as whether the subnet has an internet gateway attached which the function uses to determine whether the subnet is public or private.

Providers currently supported by this function

• EKS cluster clusters.eks.upbound.io

Example status patch output

status.aws.subnets

    subnets:
    - availabilityZone: eu-central-1c
      cidrBlock: 192.168.128.0/19
      id: subnet-11111111111111111
      ipv6CidrBlock: ""
      isIpV6: false
      isPublic: false
      tags: {}
    - availabilityZone: eu-central-1b
      cidrBlock: 192.168.64.0/19
      id: subnet-22222222222222222
      ipv6CidrBlock: ""
      isIpV6: false
      isPublic: true
      tags: {}
    - availabilityZone: eu-central-1b
      cidrBlock: 192.168.160.0/19
      id: subnet-33333333333333333
      ipv6CidrBlock: ""
      isIpV6: false
      isPublic: false
      tags: {}
    - availabilityZone: eu-central-1a
      cidrBlock: 192.168.96.0/19
      id: subnet-44444444444444444
      ipv6CidrBlock: ""
      isIpV6: false
      isPublic: false
      tags: {}
    - availabilityZone: eu-central-1c
      cidrBlock: 192.168.32.0/19
      id: subnet-555555555555555555
      ipv6CidrBlock: ""
      isIpV6: false
      isPublic: true
      tags: {}
    - availabilityZone: eu-central-1a
      cidrBlock: 192.168.0.0/19
      id: subnet-6666666666666666666
      ipv6CidrBlock: ""
      isIpV6: false
      isPublic: true
      tags: {}

Installing

apiVersion: pkg.crossplane.io/v1beta1
kind: Function
metadata:
  name: function-generate-subnets
spec:
  package: docker.io/giantswarm/crossplane-fn-generate-subnets:v0.1.0

Building

# Run code generation - see input/generate.go
$ go generate ./...

# Lint the code
$ docker run --rm -v $(pwd):/app -v ~/.cache/golangci-lint/v1.54.2:/root/.cache -w /app golangci/golangci-lint:v1.54.2 golangci-lint run

$ go test ./... -coverprofile=cover.out && go tool cover -html=cover.out
?       github.com/giantswarm/crossplane-fn-generate-subnets/pkg/composite/v1beta1      [no test files]
?       github.com/giantswarm/crossplane-fn-generate-subnets/pkg/input/v1beta1  [no test files]
ok      github.com/giantswarm/crossplane-fn-generate-subnets    0.022s  coverage: 72.0% of statements

# Build a Docker image - see Dockerfile
$ docker buildx build .

Testing locally

To test this application locally you need to first install crossplane-cli.

The main function contains a "fake client" to bypass the calls to AWS.

To enable this, use the flag -f

For debug logs, use the flag -d

All local testing must run in insecure mode.

go run . --insecure -df

Next, in a second window run:

crossplane beta render examples/xr.yaml examples/composition.yaml examples/functions.yaml -o examples/observed.yaml

To support different scenarios, different observed states have been created:

• notreconciled.yaml contains the cluster in an unreconciled state

  crossplane beta render examples/xr.yaml examples/composition.yaml examples/functions.yaml -o examples/notreconciled.yaml

• partial-observed.yaml returns the subnets without the atProvider reference defined

  crossplane beta render examples/xr.yaml examples/composition.yaml examples/functions.yaml -o examples/partial-observed.yaml

Known Issues

When applying the patch if the specification of the status patch in your XRD does not match the definition in definition_xrs.yaml then it is possible to invoke a situation whereby resources in the composition do not become ready. See Crossplane issue 4968 for details on how this may occur