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Kuadrant DNS

A Kuadrant DNSPolicy custom resource:

  1. Targets Gateway API networking resources Gateways to provide dns management by managing the lifecycle of dns records in external dns providers such as AWS Route53 and Google DNS.

How it works

A DNSPolicy and its targeted Gateway API networking resource contain all the statements to configure both the ingress gateway and the external DNS service. The needed dns names are gathered from the listener definitions and the IPAdresses | CNAME hosts are gathered from the status block of the gateway resource.

The DNSPolicy custom resource

Overview

The DNSPolicy spec includes the following parts:

  • A reference to an existing Gateway API resource (spec.targetRef)
  • LoadBalancing specification (spec.loadBalancing)
  • HealthCheck specification (spec.healthCheck)

High-level example and field definition

apiVersion: kuadrant.io/v1
kind: DNSPolicy
metadata:
  name: my-dns-policy
spec:
  # reference to an existing networking resource to attach the policy to
  # it can only be a Gateway API Gateway resource
  # it can only refer to objects in the same namespace as the DNSPolicy
  # it can target a specific listener using sectionName 
  targetRef:
    group: gateway.networking.k8s.io
    kind: Gateway
    name: mygateway
    sectionName: api # (optional) if not set policy applies to all listeners that do not have a policy attached directly
    
 # reference to an existing secret resource containing provider credentials and configuration
 # it can only refer to Secrets in the same namespace as the DNSPolicy that have the type kuadrant.io/(provider) e.g kuadrant.io/aws
  providerRefs:
   - name: my-aws-credentials
 
  # (optional) loadbalancing specification
  # use it for providing the specification of how dns will be configured in order to provide balancing of requests across multiple clusters. If not configured, a simple A or CNAME record will be created. If you have a policy with no loadbalancing defined and want to move to a loadbalanced configuration, you will need to delete and re-create the policy.
  loadBalancing:
    # is this the default geo to be applied to records. It is important that you set the default geo flag to true **Only** for the GEO value you wish to act as the catchall GEO, you should not set multiple GEO values as default for a given targeted listener. Example: policy 1 targets listener 1 with a geo of US and sets default to true. Policy 2 targets a listener on another cluster and set the geo to EU and default to false. It is fine for policies in the same default GEO to set the value to true. The main thing is to have only one unique GEO set as the default for any shared listener hostname.
    defaultGeo: true
    # weighted specification. This will apply the given weight to the records created based on the targeted gateway listeners. If you have multiple gateways that share a listener host, you can set different weight values to influence how much traffic will be brought to a given gateway.
    weight: 100
    # This is the actual GEO location to set for records created by this policy. This can and should be different if you have multiple gateways across multiple geographic areas. 
    
    # AWS: To see all regions supported by AWS Route 53, please see the official (documentation)[https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/resource-record-sets-values-geo.html]. With Route 53 when setting a continent code use a "GEO-" prefix otherwise it will be considered a country code. 
    
    # GCP: To see all regions supported by GCP Cloud DNS, please see the official (documentation)[https://cloud.google.com/compute/docs/regions-zones]
    
    #To see the different values you can use for the geo based DNS with Azure take a look at the following (documentation)[https://learn.microsoft.com/en-us/azure/traffic-manager/traffic-manager-geographic-regions]
    geo: IE

  # (optional) health check specification
  # health check probes with the following specification will be created for each DNS target, these probes constantly check that the endpoint can be reached. They will flag an unhealthy endpoint in the status. If no DNSRecord has yet been published and the endpoint is unhealthy, the record will not be published until the health check passes.
  healthCheck:
    # the path on the listener host(s) that you want to check. 
    path: /health
    # how many times does the health check need to fail before unhealthy.
    failureThreshold: 3
    # how often should it be checked.
    interval: 5min
    # additionalHeadersRef is reference to a local secret with a set of key value pairs to be used as headers when sending the health check request.
    additionalHeadersRef:
      name: headers

Check out the API reference for a full specification of the DNSPolicy CRD.

Using the DNSPolicy

DNS Provider Setup

A DNSPolicy acts against a target Gateway by processing its listeners for hostnames that it can create dns records for. In order for it to do this, it must know about the dns provider. This is done through the creation of dns provider secrets containing the credentials and configuration for the dns provider account.

If for example a Gateway is created with a listener with a hostname of echo.apps.hcpapps.net:

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: my-gw
spec:
  listeners:
    - allowedRoutes:
        namespaces:
          from: All
      name: api
      hostname: echo.apps.hcpapps.net
      port: 80
      protocol: HTTP

In order for the DNSPolicy to act upon that listener, a DNS provider Secret must exist for that hostnames' domain.

apiVersion: v1
kind: Secret
metadata:
  name: my-aws-credentials
  namespace: <Gateway Namespace>
data:
  AWS_ACCESS_KEY_ID: <AWS_ACCESS_KEY_ID>
  AWS_REGION: <AWS_REGION>
  AWS_SECRET_ACCESS_KEY: <AWS_SECRET_ACCESS_KEY>
type: kuadrant.io/aws

By default, Kuadrant will list the available zones and find the matching zone based on the listener host in the gateway listener. If it finds more than one matching zone for a given listener host, it will not update any of those zones. When providing a credential you should limit that credential down to just have write access to the zones you want Kuadrant to manage. Below is an example of a an AWS policy for doing this type of thing:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "route53:ListTagsForResources",
                "route53:GetHealthCheckLastFailureReason",
                "route53:GetHealthCheckStatus",
                "route53:GetChange",
                "route53:GetHostedZone",
                "route53:ChangeResourceRecordSets",
                "route53:ListResourceRecordSets",
                "route53:GetHealthCheck",
                "route53:UpdateHostedZoneComment",
                "route53:UpdateHealthCheck",
                "route53:CreateHealthCheck",
                "route53:DeleteHealthCheck",
                "route53:ListTagsForResource",
                "route53:ListHealthChecks",
                "route53:GetGeoLocation",
                "route53:ListGeoLocations",
                "route53:ListHostedZonesByName",
                "route53:GetHealthCheckCount"
            ],
            "Resource": [
                "arn:aws:route53:::hostedzone/Z08187901Y93585DDGM6K",
                "arn:aws:route53:::healthcheck/*",
                "arn:aws:route53:::change/*"
            ]
        },
        {
            "Sid": "VisualEditor1",
            "Effect": "Allow",
            "Action": [
                "route53:ListHostedZones"
            ],
            "Resource": "*"
        }
    ]
}

Targeting a Gateway networking resource

When a DNSPolicy targets a Gateway, the policy will be enforced on all gateway listeners.

Target a Gateway by setting the spec.targetRef field of the DNSPolicy as follows:

apiVersion: kuadrant.io/v1beta2
kind: DNSPolicy
metadata:
  name: <DNSPolicy name>
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: Gateway
    name: <Gateway Name>

Targeting a specific Listener of a gateway

A DNSPolicy can target a specific listener in a gateway using the sectionName property of the targetRef configuration. When you set the sectionName, the DNSPolicy will only affect that listener and no others. If you also have another DNSPolicy targeting the entire gateway, the more specific policy targeting the listerner will be the policy that is applied.

apiVersion: kuadrant.io/v1beta2
kind: DNSPolicy
metadata:
  name: <DNSPolicy name>
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: Gateway
    name: <Gateway Name>
    sectionName: <myListenerName>

DNSRecord Resource

The DNSPolicy will create a DNSRecord resource for each listener hostname. The DNSPolicy resource uses the status of the Gateway to determine what dns records need to be created based on the clusters it has been placed onto.

Given the following multi cluster gateway status:

status:
  addresses:
    - type: kuadrant.io/MultiClusterIPAddress
      value: kind-mgc-workload-1/172.31.201.1
    - type: kuadrant.io/MultiClusterIPAddress
      value: kind-mgc-workload-2/172.31.202.1
  listeners:
    - attachedRoutes: 1
      conditions: []
      name: kind-mgc-workload-1.api
      supportedKinds: []
    - attachedRoutes: 1
      conditions: []
      name: kind-mgc-workload-2.api
      supportedKinds: []

A DNSPolicy targeting this gateway would create an appropriate DNSRecord based on the routing strategy selected.

loadbalanced

apiVersion: kuadrant.io/v1alpha1
kind: DNSRecord
metadata:
  name: echo.apps.hcpapps.net
  namespace: <Gateway Namespace>
spec:
  endpoints:
    - dnsName: 24osuu.lb-2903yb.echo.apps.hcpapps.net
      recordTTL: 60
      recordType: A
      targets:
        - 172.31.202.1
    - dnsName: default.lb-2903yb.echo.apps.hcpapps.net
      providerSpecific:
        - name: weight
          value: "120"
      recordTTL: 60
      recordType: CNAME
      setIdentifier: 24osuu.lb-2903yb.echo.apps.hcpapps.net
      targets:
        - 24osuu.lb-2903yb.echo.apps.hcpapps.net
    - dnsName: default.lb-2903yb.echo.apps.hcpapps.net
      providerSpecific:
        - name: weight
          value: "120"
      recordTTL: 60
      recordType: CNAME
      setIdentifier: lrnse3.lb-2903yb.echo.apps.hcpapps.net
      targets:
        - lrnse3.lb-2903yb.echo.apps.hcpapps.net
    - dnsName: echo.apps.hcpapps.net
      recordTTL: 300
      recordType: CNAME
      targets:
        - lb-2903yb.echo.apps.hcpapps.net
    - dnsName: lb-2903yb.echo.apps.hcpapps.net
      providerSpecific:
        - name: geo-country-code
          value: '*'
      recordTTL: 300
      recordType: CNAME
      setIdentifier: default
      targets:
        - default.lb-2903yb.echo.apps.hcpapps.net
    - dnsName: lrnse3.lb-2903yb.echo.apps.hcpapps.net
      recordTTL: 60
      recordType: A
      targets:
        - 172.31.201.1
  providerRefs:
    - name: my-aws-credentials

After DNSRecord reconciliation the listener hostname should be resolvable through dns:

dig echo.apps.hcpapps.net +short
lb-2903yb.echo.apps.hcpapps.net.
default.lb-2903yb.echo.apps.hcpapps.net.
lrnse3.lb-2903yb.echo.apps.hcpapps.net.
172.31.201.1

simple

apiVersion: kuadrant.io/v1alpha1
kind: DNSRecord
metadata:
  name: echo.apps.hcpapps.net
  namespace: <Gateway Namespace>
spec:
  endpoints:
    - dnsName: echo.apps.hcpapps.net
      recordTTL: 60
      recordType: A
      targets:
        - 172.31.201.1
        - 172.31.202.1
  providerRefs:
   - name: my-aws-credentials

After DNSRecord reconciliation the listener hostname should be resolvable through dns:

dig echo.apps.hcpapps.net +short
172.31.201.1

Known limitations

  • One Gateway can only be targeted by one DNSPolicy unless subsequent DNSPolicies choose to specific a sectionName in their targetRef.
  • DNSPolicies can only target Gateways defined within the same namespace of the DNSPolicy.