The f5-virtualserver source sandbox

This repository can be used as inspiration for adding a new external-dns source, basically a source to use when creating DNS records in a specific provider e.g. AWS (Route 53) or Designate (OpenStack).

In this sandbox i've created a new source to create DNS records based on F5 Networks VirtualServer CRDs. There's two fields in the VirtualServer CRD that is of interest, the host and the virtualServerAddress fields.

To test this out i've build external-dns locally and create a kind cluster, when i start external-dns locally it'll connect to the `` cluster and start to watch for VirtualServer CRDs.

One awesome feature in external-dns is that you can use the inmemory provider to store DNS records in memory, you don't need something live to connect to. Useful to do some manual testing of external-dns.

Please note that the f5-virtualserver source will enumerate all VirtualServers in the cluster, some virtual servers will have a static IP address assigned others through an IPAM controller that writes the IP address in the status field of the VirtualServer. The vs-status-updater directory in this repository includes code to do exactly that, write to the status field. This code can be used to test both scenarios.

First time

1. Clone your external-dns fork, or the upstream repository directly.

2. Optional: Checkout a (feature) branch.

3. Create the kind cluster:

kind create cluster --config=kind/dev-cluster.yaml

4. Install the CRDs shipped from F5 Networks (defined as part of the k8s-bigip-ctlr repository):

kubectl create -f https://raw.githubusercontent.com/F5Networks/k8s-bigip-ctlr/refs/heads/master/docs/cis-20.x/config_examples/customResourceDefinitions/stable/customresourcedefinitions.yml

5. Build external-dns locally:

make build

Testing with a VirtualServer with a static IP address configured

1. Start external-dns:

./build/external-dns \
  --source=f5-virtualserver \
  --provider=inmemory \
  --log-level=debug \
  --policy=upsert-only \
  --registry=txt \
  --interval=1m \
  --txt-owner-id=external-dns-cluster \
  --domain-filter=example.com

2. Create the VirtualServer object:

kubectl create -f manifests/virtualserver-static.yaml

3. See the logs of external-dns.

Testing with a VirtualServer with a dynamically configured IP address (via the included vs-status-updater)

1. Start external-dns:

./build/external-dns \
  --source=f5-virtualserver \
  --provider=inmemory \
  --log-level=debug \
  --policy=upsert-only \
  --registry=txt \
  --interval=1m \
  --txt-owner-id=external-dns-cluster \
  --domain-filter=example.com

2. Create the VirtualServer object:

kubectl create -f manifests/virtualserver-ipam.yaml

3. Run the vs-status-updater, without flags accepting the sane defaults:

cd vs-status-updater
go run main.go

or with flags:

cd vs-status-updater
go run main.go -namespace "default" -vs-name "example-vs-ipam" -vs-address "192.168.1.101" -status "Ok"

Now updated the status of the VirtualServer:

go run main.go -namespace "default" -vs-name "example-vs-ipam" -vs-address "" -status "Error"

This will update the status field of the VirtualServer called example-vs-ipam in the default namespace. With the flags you can reconfigure the status field as it would've been done when running a real F5 IPAM controller.

At the moment we're not handling cases when the status.status field of the VirtualServer is not Ok e.g. "" or ERROR which means that we don't exit early in the f5-virtualserver source. If we end up with a status of e.g. ERROR external-dns will still try to create a record AND upsert (basically removing the old one), the record it tries to create is of type CNAME, which is valid and it makes sense.

Testing with the DNSEndpoint CRD

You'll see external-dns create records in the inmemory provider by watching the standard output of the external-dns binary. If you want to test the crd source, which watches for DNSEndpoint CRDs (provided by external-dns):

1. Install the CRD:

kubectl create -f https://raw.githubusercontent.com/kubernetes-sigs/external-dns/master/docs/contributing/crd-source/crd-manifest.yaml

2. Create a DNSEndpoint object:

kubectl create -f manifests/dnsendpoint.yaml