feat: add annotation and label filters to Ambassador Host Source (#2633)

* Add annotation filter to Ambassador Host Source

This change makes the Ambassador Host source respect the External-DNS annotationFilter allowing for an Ambassador Host resource to specify what External-DNS deployment to use when there are multiple External-DNS deployments within the same cluster. Before this change if you had two External-DNS deployments within the cluster and used the Ambassador Host source the first External-DNS to process the resource will create the record and not the one that was specified in the filter annotation.

I added the `filterByAnnotations` function so that it matched the same way the other sources have implemented annotation filtering. I didn't add the controller check only because I wanted to keep this change to implementing the annotationFilter.

Example: Create two External-DNS deployments 1 public and 1 private and set the Ambassador Host to use the public External-DNS using the annotation filter.

```
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns-private
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns-private
  template:
    metadata:
      labels:
        app: external-dns-private
      annotations:
        iam.amazonaws.com/role: {ARN} # AWS ARN role
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:latest
        args:
        - --source=ambassador-host
        - --domain-filter=example.net # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
        - --provider=aws
        - --policy=upsert-only # would prevent ExternalDNS from deleting any records, omit to enable full synchronization
        - --aws-zone-type=private # only look at public hosted zones (valid values are public, private or no value for both)
        - --registry=txt
        - --txt-owner-id= {Hosted Zone ID} # Insert Route53 Hosted Zone ID here
        - --annotation-filter=kubernetes.io/ingress.class in (private)
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns-public
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns-public
  template:
    metadata:
      labels:
        app: external-dns-public
      annotations:
        iam.amazonaws.com/role: {ARN} # AWS ARN role
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:latest
        args:
        - --source=ambassador-host
        - --domain-filter=example.net # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
        - --provider=aws
        - --policy=upsert-only # would prevent ExternalDNS from deleting any records, omit to enable full synchronization
        - --aws-zone-type= # only look at public hosted zones (valid values are public, private or no value for both)
        - --registry=txt
        - --txt-owner-id= {Hosted Zone ID} # Insert Route53 Hosted Zone ID here
        - --annotation-filter=kubernetes.io/ingress.class in (public)
---
apiVersion: getambassador.io/v3alpha1
  kind: Host
  metadata:
    name: your-hostname
    annotations:
      external-dns.ambassador-service: emissary-ingress/emissary
      kubernetes.io/ingress.class: public
  spec:
		acmeProvider:
      authority: none
		hostname: your-hostname.example.com
```

Fixes #2632

* Add Label filltering for Ambassador Host source

Currently the `--label-filter` flag can only be used to filter CRDs, Ingress, Service and Openshift Route objects which match the label selector passed through that flag. This change extends the functionality to the Ambassador Host type object.

When the flag is not specified the default value is `labels.Everything()` which is an empty string, the same as before. An annotation based filter is inefficient because the filtering has to be done in the controller instead of the API server like with label filtering. The Annotation based filtering has been left in for legacy reasons so the Ambassador Host source can be used inconjunction with the other sources that don't yet support label filltering.

It is possible to use label based filltering with annotation based filltering so you can initially filter by label then filter the returned hosts by annotation. This is not recomended

* Update Ambassador Host source docs

Add that the Ambassador Host source now supports both annotation and label filltering.

docs/sources/sources.md

@@ -2,7 +2,7 @@
 
 | Source | Resources | annotation-filter | label-filter |
 |---------------------------------|-------------------------------------------------------------------------------|-------------------|--------------|
-| ambassador-host | Host.getambassador.io |  |  |
+| ambassador-host | Host.getambassador.io | Yes | Yes |
 | connector | | | |
 | contour-httpproxy | HttpProxy.projectcontour.io | Yes | |
 | cloudfoundry | | | |

pkg/apis/externaldns/types.go

@@ -430,7 +430,7 @@ func (cfg *Config) ParseFlags(args []string) error {
  app.Flag("openshift-router-name", "if source is openshift-route then you can pass the ingress controller name. Based on this name external-dns will select the respective router from the route status and map that routerCanonicalHostname to the route host while creating a CNAME record.").StringVar(&cfg.OCPRouterName)
  app.Flag("namespace", "Limit resources queried for endpoints to a specific namespace (default: all namespaces)").Default(defaultConfig.Namespace).StringVar(&cfg.Namespace)
  app.Flag("annotation-filter", "Filter resources queried for endpoints by annotation, using label selector semantics").Default(defaultConfig.AnnotationFilter).StringVar(&cfg.AnnotationFilter)
- app.Flag("label-filter", "Filter resources queried for endpoints by label selector; currently supported by source types crd, gateway-httproute, gateway-grpcroute, gateway-tlsroute, gateway-tcproute, gateway-udproute, ingress, node, openshift-route, and service").Default(defaultConfig.LabelFilter).StringVar(&cfg.LabelFilter)
+ app.Flag("label-filter", "Filter resources queried for endpoints by label selector; currently supported by source types crd, gateway-httproute, gateway-grpcroute, gateway-tlsroute, gateway-tcproute, gateway-udproute, ingress, node, openshift-route, service and ambassador-host").Default(defaultConfig.LabelFilter).StringVar(&cfg.LabelFilter)
  app.Flag("ingress-class", "Require an Ingress to have this class name (defaults to any class; specify multiple times to allow more than one class)").StringsVar(&cfg.IngressClassNames)
  app.Flag("fqdn-template", "A templated string that's used to generate DNS names from sources that don't define a hostname themselves, or to add a hostname suffix when paired with the fake source (optional). Accepts comma separated list for multiple global FQDN.").Default(defaultConfig.FQDNTemplate).StringVar(&cfg.FQDNTemplate)
  app.Flag("combine-fqdn-annotation", "Combine FQDN template and Annotations instead of overwriting").BoolVar(&cfg.CombineFQDNAndAnnotation)

source/ambassador_host.go

@@ -57,8 +57,10 @@ type ambassadorHostSource struct {
  dynamicKubeClient dynamic.Interface
  kubeClient kubernetes.Interface
  namespace string
+ annotationFilter string
  ambassadorHostInformer informers.GenericInformer
  unstructuredConverter *unstructuredConverter
+ labelSelector labels.Selector
 }
 
 // NewAmbassadorHostSource creates a new ambassadorHostSource with the given config.
@@ -67,6 +69,8 @@ func NewAmbassadorHostSource(
  dynamicKubeClient dynamic.Interface,
  kubeClient kubernetes.Interface,
  namespace string,
+ annotationFilter string,
+ labelSelector labels.Selector,
 ) (Source, error) {
  var err error
 
@@ -85,6 +89,7 @@ func NewAmbassadorHostSource(
 
  informerFactory.Start(ctx.Done())
 
+ // wait for the local cache to be populated.
  if err := waitForDynamicCacheSync(context.Background(), informerFactory); err != nil {
  return nil, err
  }
@@ -98,20 +103,23 @@ func NewAmbassadorHostSource(
  dynamicKubeClient: dynamicKubeClient,
  kubeClient: kubeClient,
  namespace: namespace,
+ annotationFilter: annotationFilter,
  ambassadorHostInformer: ambassadorHostInformer,
  unstructuredConverter: uc,
+ labelSelector: labelSelector,
  }, nil
 }
 
 // Endpoints returns endpoint objects for each host-target combination that should be processed.
 // Retrieves all Hosts in the source's namespace(s).
 func (sc *ambassadorHostSource) Endpoints(ctx context.Context) ([]*endpoint.Endpoint, error) {
- hosts, err := sc.ambassadorHostInformer.Lister().ByNamespace(sc.namespace).List(labels.Everything())
+ hosts, err := sc.ambassadorHostInformer.Lister().ByNamespace(sc.namespace).List(sc.labelSelector)
  if err != nil {
  return nil, err
  }
 
- endpoints := []*endpoint.Endpoint{}
+ // Get a list of Ambassador Host resources
+ ambassadorHosts := []*ambassador.Host{}
  for _, hostObj := range hosts {
  unstructuredHost, ok := hostObj.(*unstructured.Unstructured)
  if !ok {
@@ -123,7 +131,18 @@ func (sc *ambassadorHostSource) Endpoints(ctx context.Context) ([]*endpoint.Endp
  if err != nil {
  return nil, err
  }
+ ambassadorHosts = append(ambassadorHosts, host)
+ }
+
+ // Filter Ambassador Hosts
+ ambassadorHosts, err = sc.filterByAnnotations(ambassadorHosts)
+ if err != nil {
+ return nil, errors.Wrap(err, "failed to filter Ambassador Hosts by annotation")
+ }
 
+ endpoints := []*endpoint.Endpoint{}
+
+ for _, host := range ambassadorHosts {
  fullname := fmt.Sprintf("%s/%s", host.Namespace, host.Name)
 
  // look for the "exernal-dns.ambassador-service" annotation. If it is not there then just ignore this `Host`
@@ -269,3 +288,35 @@ func newUnstructuredConverter() (*unstructuredConverter, error) {
 
  return uc, nil
 }
+
+// Filter a list of Ambassador Host Resources to only return the ones that
+// contain the required External-DNS annotation filter
+func (sc *ambassadorHostSource) filterByAnnotations(ambassadorHosts []*ambassador.Host) ([]*ambassador.Host, error) {
+ // External-DNS Annotation Filter
+ labelSelector, err := metav1.ParseToLabelSelector(sc.annotationFilter)
+ if err != nil {
+ return nil, err
+ }
+
+ selector, err := metav1.LabelSelectorAsSelector(labelSelector)
+ if err != nil {
+ return nil, err
+ }
+
+ // empty filter returns original list of Ambassador Hosts
+ if selector.Empty() {
+ return ambassadorHosts, nil
+ }
+
+ // Return a filtered list of Ambassador Hosts
+ filteredList := []*ambassador.Host{}
+ for _, host := range ambassadorHosts {
+ annotations := labels.Set(host.Annotations)
+ // include Ambassador Host if its annotations match the annotation filter
+ if selector.Matches(annotations) {
+ filteredList = append(filteredList, host)
+ }
+ }
+
+ return filteredList, nil
+}