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ExternalDNS - Vultr Webhook

ExternalDNS is a Kubernetes add-on for automatically managing Domain Name System (DNS) records for Kubernetes services by using different DNS providers. By default, Kubernetes manages DNS records internally, but ExternalDNS takes this functionality a step further by delegating the management of DNS records to an external DNS provider such as this one. Therefore, the Vultr webhook allows to manage your Vultr domains inside your kubernetes cluster with ExternalDNS.

To use ExternalDNS with Vultr, you need your Vultr API token of the account managing your domains. For detailed technical instructions on how the Vultr webhook is deployed using the Bitnami Helm charts for ExternalDNS, seedeployment instructions.

Kubernetes Deployment

The deployment can be performed in every way Kubernetes supports. The following example shows the deployment as a sidecar container in the ExternalDNS pod using the Bitnami Helm charts for ExternalDNS.

⚠️ This webhook requires at least ExternalDNS v0.14.0.

The webhook can be installed using either the Bitnami chart or the ExternalDNS one.

First, create the Vultr secret:

kubectl create secret generic vultr-credentials --from-literal=api-key='<EXAMPLE_PLEASE_REPLACE>' -n external-dns

Using the Bitnami chart

Skip this if you already have the Bitnami repository added:

helm repo add bitnami https://charts.bitnami.com/bitnami

You can then create the helm values file, for example external-dns-vultr-values.yaml:

image:
  registry: registry.k8s.io
  repository: external-dns/external-dns
  tag: v0.14.0

provider: webhook

extraArgs:
  webhook-provider-url: http://localhost:8888
  txt-prefix: reg-

sidecars:
  - name: vultr-webhook
    image: vultr/external-dns-vultr-webhook:v0.1.0
    ports:
      - containerPort: 8888
        name: webhook
      - containerPort: 8080
        name: http
    livenessProbe:
      httpGet:
        path: /health
        port: http
      initialDelaySeconds: 10
      timeoutSeconds: 5
    readinessProbe:
      httpGet:
        path: /ready
        port: http
      initialDelaySeconds: 10
      timeoutSeconds: 5
    env:
      - name: VULTR_API_KEY
        valueFrom:
          secretKeyRef:
            name: vultr-credentials
            key: api-key

And then:

# install external-dns with helm
helm install external-dns-vultr bitnami/external-dns -f external-dns-vultr-values.yaml -n external-dns

Using the ExternalDNS chart

Skip this if you already have the ExternalDNS repository added:

helm repo add external-dns https://kubernetes-sigs.github.io/external-dns/

You can then create the helm values file, for example external-dns-vultr-values.yaml:

namespace: external-dns
policy: sync
provider:
  name: webhook
  webhook:
    image:
      repository: vultr/external-dns-vultr-webhook
      tag: v0.1.0
    env:
      - name: VULTR_API_KEY
        valueFrom:
          secretKeyRef:
            name: vultr-credentials
            key: api-key
    livenessProbe:
      httpGet:
        path: /health
        port: http-wh-metrics
      initialDelaySeconds: 10
      timeoutSeconds: 5
    readinessProbe:
      httpGet:
        path: /ready
        port: http-wh-metrics
      initialDelaySeconds: 10
      timeoutSeconds: 5

extraArgs:
  - --txt-prefix=reg-

And then:

# install external-dns with helm
helm install external-dns-vultr external-dns/external-dns -f external-dns-vultr-values.yaml --version 1.14.3 -n external-dns

Environment variables

The following environment variables are available:

Variable Description Notes
VULTR_API_KEY Vultr API token Mandatory
DRY_RUN If set, changes won't be applied Default: false
WEBHOOK_HOST Webhook hostname or IP address Default: localhost
WEBHOOK_PORT Webhook port Default: 8888
HEALTH_HOST Liveness and readiness hostname Default: 0.0.0.0
HEALTH_PORT Liveness and readiness port Default: 8080
READ_TIMEOUT Servers' read timeout in ms Default: 60000
WRITE_TIMEOUT Servers' write timeout in ms Default: 60000

Additional environment variables for domain filtering:

Environment variable Description
DOMAIN_FILTER Filtered domains
EXCLUDE_DOMAIN_FILTER Excluded domains
REGEXP_DOMAIN_FILTER Regex for filtered domains
REGEXP_DOMAIN_FILTER_EXCLUSION Regex for excluded domains

If the REGEXP_DOMAIN_FILTER is set, the following variables will be used to build the filter:

  • REGEXP_DOMAIN_FILTER
  • REGEXP_DOMAIN_FILTER_EXCLUSION

otherwise, the filter will be built using:

  • DOMAIN_FILTER
  • EXCLUDE_DOMAIN_FILTER

Tweaking the configuration

While tweaking the configuration, there are some points to take into consideration:

  • if WEBHOOK_HOST and HEALTH_HOST are set to the same address/hostname or one of them is set to 0.0.0.0 remember to use different ports.

  • if your records don't get deleted when applications are uninstalled, you might want to verify the policy in use for ExternalDNS: if it's upsert-only no deletion will occur. It must be set to sync for deletions to be processed. Please add the following to external-dns-vultr-values.yaml if you want this strategy:

    policy: sync

Development

The basic development tasks are provided by make. Run make help to see the available targets.