Chapter 8. Configuring custom domains for Knative services
8.1. Configuring a custom domain for a Knative service
Knative services are automatically assigned a default domain name based on your cluster configuration. For example, <service_name>-<namespace>.example.com
. You can customize the domain for your Knative service by mapping a custom domain name that you own to a Knative service.
You can do this by creating a DomainMapping
resource for the service. You can also create multiple DomainMapping
resources to map multiple domains and subdomains to a single service.
8.2. Custom domain mapping
You can customize the domain for your Knative service by mapping a custom domain name that you own to a Knative service. To map a custom domain name to a custom resource (CR), you must create a DomainMapping
CR that maps to an Addressable target CR, such as a Knative service or a Knative route.
8.2.1. Creating a custom domain mapping
You can customize the domain for your Knative service by mapping a custom domain name that you own to a Knative service. To map a custom domain name to a custom resource (CR), you must create a DomainMapping
CR that maps to an Addressable target CR, such as a Knative service or a Knative route.
Prerequisites
- The OpenShift Serverless Operator and Knative Serving are installed on your cluster.
-
Install the OpenShift CLI (
oc
). - You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
You have created a Knative service and control a custom domain that you want to map to that service.
NoteYour custom domain must point to the IP address of the OpenShift Container Platform cluster.
Procedure
Create a YAML file containing the
DomainMapping
CR in the same namespace as the target CR you want to map to:apiVersion: serving.knative.dev/v1alpha1 kind: DomainMapping metadata: name: <domain_name> 1 namespace: <namespace> 2 spec: ref: name: <target_name> 3 kind: <target_type> 4 apiVersion: serving.knative.dev/v1
Example service domain mapping
apiVersion: serving.knative.dev/v1alpha1 kind: DomainMapping metadata: name: example.com namespace: default spec: ref: name: example-service kind: Service apiVersion: serving.knative.dev/v1
Example route domain mapping
apiVersion: serving.knative.dev/v1alpha1 kind: DomainMapping metadata: name: example.com namespace: default spec: ref: name: example-route kind: Route apiVersion: serving.knative.dev/v1
Apply the
DomainMapping
CR as a YAML file:$ oc apply -f <filename>
8.3. Custom domains for Knative services using the Knative CLI
You can customize the domain for your Knative service by mapping a custom domain name that you own to a Knative service. You can use the Knative (kn
) CLI to create a DomainMapping
custom resource (CR) that maps to an Addressable target CR, such as a Knative service or a Knative route.
8.3.1. Creating a custom domain mapping by using the Knative CLI
Prerequisites
- The OpenShift Serverless Operator and Knative Serving are installed on your cluster.
You have created a Knative service or route, and control a custom domain that you want to map to that CR.
NoteYour custom domain must point to the DNS of the OpenShift Container Platform cluster.
-
You have installed the Knative (
kn
) CLI. - You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
Procedure
Map a domain to a CR in the current namespace:
$ kn domain create <domain_mapping_name> --ref <target_name>
Example command
$ kn domain create example.com --ref example-service
The
--ref
flag specifies an Addressable target CR for domain mapping.If a prefix is not provided when using the
--ref
flag, it is assumed that the target is a Knative service in the current namespace.Map a domain to a Knative service in a specified namespace:
$ kn domain create <domain_mapping_name> --ref <ksvc:service_name:service_namespace>
Example command
$ kn domain create example.com --ref ksvc:example-service:example-namespace
Map a domain to a Knative route:
$ kn domain create <domain_mapping_name> --ref <kroute:route_name>
Example command
$ kn domain create example.com --ref kroute:example-route
8.4. Domain mapping using the Developer perspective
You can customize the domain for your Knative service by mapping a custom domain name that you own to a Knative service. You can use the Developer perspective of the OpenShift Container Platform web console to map a DomainMapping
custom resource (CR) to a Knative service.
8.4.1. Mapping a custom domain to a service by using the Developer perspective
Prerequisites
- You have logged in to the web console.
- You are in the Developer perspective.
- The OpenShift Serverless Operator and Knative Serving are installed on your cluster. This must be completed by a cluster administrator.
- You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads in OpenShift Container Platform.
You have created a Knative service and control a custom domain that you want to map to that service.
NoteYour custom domain must point to the IP address of the OpenShift Container Platform cluster.
Procedure
- Navigate to the Topology page.
-
Right-click on the service that you want to map to a domain, and select the Edit option that contains the service name. For example, if the service is named
example-service
, select the Edit example-service option. In the Advanced options section, click Show advanced Routing options.
- If the domain mapping CR that you want to map to the service already exists, you can select it in the Domain mapping list.
-
If you want to create a new domain mapping CR, type the domain name into the box, and select the Create option. For example, if you type in
example.com
, the Create option is Create "example.com".
- Click Save to save the changes to your service.
Verification
- Navigate to the Topology page.
- Click on the service that you have created.
- In the Resources tab of the service information window, you can see the domain you have mapped to the service listed under Domain mappings.
8.5. Domain mapping using the Administrator perspective
If you do not want to switch to the Developer perspective in the OpenShift Container Platform web console or use the Knative (kn
) CLI or YAML files, you can use the Administator perspective of the OpenShift Container Platform web console.
8.5.1. Mapping a custom domain to a service by using the Administrator perspective
Knative services are automatically assigned a default domain name based on your cluster configuration. For example, <service_name>-<namespace>.example.com
. You can customize the domain for your Knative service by mapping a custom domain name that you own to a Knative service.
You can do this by creating a DomainMapping
resource for the service. You can also create multiple DomainMapping
resources to map multiple domains and subdomains to a single service.
If you have cluster administrator permissions on OpenShift Container Platform (or cluster or dedicated administrator permissions on OpenShift Dedicated or Red Hat OpenShift Service on AWS), you can create a DomainMapping
custom resource (CR) by using the Administrator perspective in the web console.
Prerequisites
- You have logged in to the web console.
- You are in the Administrator perspective.
- You have installed the OpenShift Serverless Operator.
- You have installed Knative Serving.
- You have created a project or have access to a project with the appropriate roles and permissions to create applications and other workloads.
You have created a Knative service and control a custom domain that you want to map to that service.
NoteYour custom domain must point to the IP address of the cluster.
Procedure
- Navigate to CustomResourceDefinitions and use the search box to find the DomainMapping custom resource definition (CRD).
- Click the DomainMapping CRD, then navigate to the Instances tab.
- Click Create DomainMapping.
Modify the YAML for the
DomainMapping
CR so that it includes the following information for your instance:apiVersion: serving.knative.dev/v1alpha1 kind: DomainMapping metadata: name: <domain_name> 1 namespace: <namespace> 2 spec: ref: name: <target_name> 3 kind: <target_type> 4 apiVersion: serving.knative.dev/v1
Example domain mapping to a Knative service
apiVersion: serving.knative.dev/v1alpha1 kind: DomainMapping metadata: name: custom-ksvc-domain.example.com namespace: default spec: ref: name: example-service kind: Service apiVersion: serving.knative.dev/v1
Verification
Access the custom domain by using a
curl
request. For example:Example command
$ curl custom-ksvc-domain.example.com
Example output
Hello OpenShift!
8.6. Securing a mapped service using a TLS certificate
8.6.1. Securing a service with a custom domain by using a TLS certificate
After you have configured a custom domain for a Knative service, you can use a TLS certificate to secure the mapped service. To do this, you must create a Kubernetes TLS secret, and then update the DomainMapping
CR to use the TLS secret that you have created.
If you use net-istio
for Ingress and enable mTLS via SMCP using security.dataPlane.mtls: true
, Service Mesh deploys DestinationRules
for the *.local
host, which does not allow DomainMapping
for OpenShift Serverless.
To work around this issue, enable mTLS by deploying PeerAuthentication
instead of using security.dataPlane.mtls: true
.
Prerequisites
-
You configured a custom domain for a Knative service and have a working
DomainMapping
CR. - You have a TLS certificate from your Certificate Authority provider or a self-signed certificate.
-
You have obtained the
cert
andkey
files from your Certificate Authority provider, or a self-signed certificate. -
Install the OpenShift CLI (
oc
).
Procedure
Create a Kubernetes TLS secret:
$ oc create secret tls <tls_secret_name> --cert=<path_to_certificate_file> --key=<path_to_key_file>
Add the
networking.internal.knative.dev/certificate-uid: <id>`
label to the Kubernetes TLS secret:$ oc label secret <tls_secret_name> networking.internal.knative.dev/certificate-uid="<id>"
If you are using a third-party secret provider such as cert-manager, you can configure your secret manager to label the Kubernetes TLS secret automatically. Cert-manager users can use the secret template offered to automatically generate secrets with the correct label. In this case, secret filtering is done based on the key only, but this value can carry useful information such as the certificate ID that the secret contains.
NoteThe cert-manager Operator for Red Hat OpenShift is a Technology Preview feature. For more information, see the Installing the cert-manager Operator for Red Hat OpenShift documentation.
Update the
DomainMapping
CR to use the TLS secret that you have created:apiVersion: serving.knative.dev/v1alpha1 kind: DomainMapping metadata: name: <domain_name> namespace: <namespace> spec: ref: name: <service_name> kind: Service apiVersion: serving.knative.dev/v1 # TLS block specifies the secret to be used tls: secretName: <tls_secret_name>
Verification
Verify that the
DomainMapping
CR status isTrue
, and that theURL
column of the output shows the mapped domain with the schemehttps
:$ oc get domainmapping <domain_name>
Example output
NAME URL READY REASON example.com https://example.com True
Optional: If the service is exposed publicly, verify that it is available by running the following command:
$ curl https://<domain_name>
If the certificate is self-signed, skip verification by adding the
-k
flag to thecurl
command.
8.6.2. Improving net-kourier memory usage by using secret filtering
By default, the informers implementation for the Kubernetes client-go
library fetches all resources of a particular type. This can lead to a substantial overhead when many resources are available, which can cause the Knative net-kourier
ingress controller to fail on large clusters due to memory leaking. However, a filtering mechanism is available for the Knative net-kourier
ingress controller, which enables the controller to only fetch Knative related secrets. You can enable this mechanism by setting an environment variable to the KnativeServing
custom resource (CR).
If you enable secret filtering, all of your secrets need to be labeled with networking.internal.knative.dev/certificate-uid: "<id>"
. Otherwise, Knative Serving does not detect them, which leads to failures. You must label both new and existing secrets.
Prerequisites
- You have cluster administrator permissions on OpenShift Container Platform, or you have cluster or dedicated administrator permissions on Red Hat OpenShift Service on AWS or OpenShift Dedicated.
- A project that you created or that you have roles and permissions for to create applications and other workloads.
- Install the OpenShift Serverless Operator and Knative Serving.
-
Install the OpenShift CLI (
oc
).
Procedure
Set the
ENABLE_SECRET_INFORMER_FILTERING_BY_CERT_UID
variable totrue
fornet-kourier-controller
in theKnativeServing
CR:Example KnativeServing CR
apiVersion: operator.knative.dev/v1beta1 kind: KnativeServing metadata: name: knative-serving namespace: knative-serving spec: deployments: - env: - container: controller envVars: - name: ENABLE_SECRET_INFORMER_FILTERING_BY_CERT_UID value: 'true' name: net-kourier-controller