Chapter 4. Configuring OpenShift Serverless applications

4.1. Multi-container support for Serving
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You can deploy a multi-container pod by using a single Knative service. This method is useful for separating application responsibilities into smaller, specialized parts.

4.1.1. Configuring a multi-container service
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Multi-container support is enabled by default. You can create a multi-container pod by specifiying multiple containers in the service.

Procedure

Modify your service to include additional containers. Only one container can handle requests, so specify ports for exactly one container. Here is an example configuration with two containers:

Multiple containers configuration

apiVersion: serving.knative.dev/v1
kind: Service
...
spec:
  template:
    spec:
      containers:
        - name: first-container 
          image: gcr.io/knative-samples/helloworld-go
          ports:
            - containerPort: 8080 
        - name: second-container 
          image: gcr.io/knative-samples/helloworld-java

apiVersion: serving.knative.dev/v1
kind: Service
...
spec:
  template:
    spec:
      containers:
        - name: first-container

1


          image: gcr.io/knative-samples/helloworld-go
          ports:
            - containerPort: 8080

2


        - name: second-container

3


          image: gcr.io/knative-samples/helloworld-java

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1: First container configuration.
2: Port specification for the first container.
3: Second container configuration.

4.1.2. Probing a multi-container service
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You can specify readiness and liveness probes for multiple containers. This feature is not enabled by default and you must configure it using the KnativeServing custom resource (CR).

Procedure

Configure multi-container probing for your service by enabling the multi-container-probing feature in the KnativeServing CR.
Multi-container probing configuration
```
...
spec:
  config:
    features:
      "multi-container-probing": enabled 
...
```
```
...
spec:
  config:
    features:
      "multi-container-probing": enabled 
```
1
```
...
```
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1
Enabled multi-container-probing feature
Apply the updated KnativeServing CR.
```
oc apply -f <filename>
```
```
$ oc apply -f <filename>
```
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Modify your multi-container service to include the specified probes.

Multi-container probing

apiVersion: serving.knative.dev/v1
kind: Service
...
spec:
 template:
   spec:
     containers:
       - name: first-container
         image: ghcr.io/knative/helloworld-go:latest
         ports:
           - containerPort: 8080
         readinessProbe: 
           httpGet:
             port: 8080
       - name: second-container
         image: gcr.io/knative-samples/helloworld-java
         readinessProbe: 
           httpGet:
             port: 8090

apiVersion: serving.knative.dev/v1
kind: Service
...
spec:
 template:
   spec:
     containers:
       - name: first-container
         image: ghcr.io/knative/helloworld-go:latest
         ports:
           - containerPort: 8080
         readinessProbe:

1


           httpGet:
             port: 8080
       - name: second-container
         image: gcr.io/knative-samples/helloworld-java
         readinessProbe:

2


           httpGet:
             port: 8090

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1: Readiness probe of the first container
2: Readiness probe of the second container

4.1.2.1. Additional resources
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General understanding of Knative Probing

4.2. EmptyDir volumes
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emptyDir volumes are empty volumes that are created when a pod is created, and are used to provide temporary working disk space. emptyDir volumes are deleted when the pod they were created for is deleted.

4.2.1. Configuring the EmptyDir extension
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The kubernetes.podspec-volumes-emptydir extension controls whether emptyDir volumes can be used with Knative Serving. To enable using emptyDir volumes, you must modify the KnativeServing custom resource (CR) to include the following YAML:

Example KnativeServing CR

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    features:
      kubernetes.podspec-volumes-emptydir: enabled
...

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    features:
      kubernetes.podspec-volumes-emptydir: enabled
...

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4.3. Persistent Volume Claims for Serving
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Some serverless applications require permanent data storage. By configuring different volume types, you can provide data storage for Knative services. Serving supports mounting of the volume types such as secret, configMap, projected, and emptyDir.

You can configure persistent volume claims (PVCs) for your Knative services. The Persistent volume types are implemented as plugins. To determine if there are any persistent volume types available, you can check the available or installed storage classes in your cluster. Persistent volumes are supported, but require a feature flag to be enabled.

Warning

The mounting of large volumes can lead to a considerable delay in the start time of the application.

4.3.1. Enabling PVC support
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Procedure

To enable Knative Serving to use PVCs and write to them, modify the KnativeServing custom resource (CR) to include the following YAML:
Enabling PVCs with write access
```
...
spec:
  config:
    features:
      "kubernetes.podspec-persistent-volume-claim": enabled
      "kubernetes.podspec-persistent-volume-write": enabled
...
```
```
...
spec:
  config:
    features:
      "kubernetes.podspec-persistent-volume-claim": enabled
      "kubernetes.podspec-persistent-volume-write": enabled
...
```
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- The kubernetes.podspec-persistent-volume-claim extension controls whether persistent volumes (PVs) can be used with Knative Serving.
- The kubernetes.podspec-persistent-volume-write extension controls whether PVs are available to Knative Serving with the write access.

To claim a PV, modify your service to include the PV configuration. For example, you might have a persistent volume claim with the following configuration:

Note

Use the storage class that supports the access mode you are requesting. For example, you can use the ocs-storagecluster-cephfs storage class for the ReadWriteMany access mode.

The ocs-storagecluster-cephfs storage class is supported and comes from Red Hat OpenShift Data Foundation.

PersistentVolumeClaim configuration

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: example-pv-claim
  namespace: my-ns
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: ocs-storagecluster-cephfs
  resources:
    requests:
      storage: 1Gi

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: example-pv-claim
  namespace: my-ns
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: ocs-storagecluster-cephfs
  resources:
    requests:
      storage: 1Gi

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In this case, to claim a PV with write access, modify your service as follows:

Knative service PVC configuration

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  namespace: my-ns
...
spec:
 template:
   spec:
     containers:
         ...
         volumeMounts: 
           - mountPath: /data
             name: mydata
             readOnly: false
     volumes:
       - name: mydata
         persistentVolumeClaim: 
           claimName: example-pv-claim
           readOnly: false

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  namespace: my-ns
...
spec:
 template:
   spec:
     containers:
         ...
         volumeMounts:

1


           - mountPath: /data
             name: mydata
             readOnly: false
     volumes:
       - name: mydata
         persistentVolumeClaim:

2


           claimName: example-pv-claim
           readOnly: false

3

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1: Volume mount specification.
2: Persistent volume claim specification.
3: Flag that enables read-only access.

Note

To successfully use persistent storage in Knative services, you need additional configuration, such as the user permissions for the Knative container user.

4.4. Init containers
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Init containers are specialized containers that are run before application containers in a pod. They are generally used to implement initialization logic for an application, which may include running setup scripts or downloading required configurations. You can enable the use of init containers for Knative services by modifying the KnativeServing custom resource (CR).

Note

Init containers may cause longer application start-up times and should be used with caution for serverless applications, which are expected to scale up and down frequently.

4.4.1. Enabling init containers
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Prerequisites

You have installed OpenShift Serverless Operator and Knative Serving on your cluster.
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.

Procedure

Enable the use of init containers by adding the kubernetes.podspec-init-containers flag to the KnativeServing CR:

Example KnativeServing CR

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    features:
      kubernetes.podspec-init-containers: enabled
...

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    features:
      kubernetes.podspec-init-containers: enabled
...

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4.5. Startup probes
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Startup probes verify whether a service has started successfully, helping to reduce cold start times for containers with slow startup processes. Startup probes run only during the container’s initialization phase and do not execute periodically. If a startup probe fails, the container adheres to the defined restartPolicy.

4.5.1. Progress deadline
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By default, services have a progress deadline that defines the time limit for a service to complete its initial startup. When using startup probes, ensure that the progress deadline is set to exceed the maximum time required by the startup probes. If the progress deadline is set too low, the startup probes might not finish before the deadline is reached, which can prevent the service from starting.

Consider increasing the progress deadline if you encounter any of these conditions in your deployment:

The service image takes a long time to pull due to its size.
The service takes a long time to become READY because of initial cache priming.
The cluster relies on autoscaling to allocate resources for new pods.

4.5.2. Configuring startup probing
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For OpenShift Serverless Serving, startup probes are not defined by default. You can define startup probes for your containers in your deployment configuration.

Procedure

Define startup probes for your service by modifying your deployment configuration. The following example shows a configuration with two containers:

Example of defined starup probes

apiVersion: serving.knative.dev/v1
kind: Service
# ...
spec:
  template:
    spec:
       containers:
        - name: first-container
          image: <image>
          ports:
            - containerPort: 8080
          # ...
          startupProbe: 
          httpGet:
            port: 8080
            path: "/"
        - name: second-container
          image: <image>
          # ...
          startupProbe: 
          httpGet:
            port: 8081
            path: "/"

apiVersion: serving.knative.dev/v1
kind: Service
# ...
spec:
  template:
    spec:
       containers:
        - name: first-container
          image: <image>
          ports:
            - containerPort: 8080
          # ...
          startupProbe:

1


          httpGet:
            port: 8080
            path: "/"
        - name: second-container
          image: <image>
          # ...
          startupProbe:

2


          httpGet:
            port: 8081
            path: "/"

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1: Startup probe of the first-container.
2: Startup probe of the second-container.

4.5.3. Configuring the progress deadline
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You can configure progress deadline settings to specify the maximum time allowed for your deployment to progress before the system reports a failure for the Knative Revision. This time limit can be specified in seconds or minutes.

To configure the progress deadline effectively, consider the following parameters:

initialDelaySeconds
failureThreshold
periodSeconds
timeoutSeconds

If the initial scale is not achieved within the specified time limit, the Knative Autoscaler component scales the revision to 0, and the Knative service enters a terminal Failed state.

By default, the progress deadline is set to 600 seconds. This value is specified as a Golang time.Duration string and must be rounded to the nearest second.

Procedure

To configure the progress deadline setting, use an annotation in your deployment configuration.

Example of progress deadline set to 60 seconds

apiVersion: serving.knative.dev/v1
kind: Service
...
spec:
  template:
    metadata:
       annotations:
            serving.knative.dev/progress-deadline: "60s"
    spec:
        containers:
            - image: ghcr.io/knative/helloworld-go:latest

apiVersion: serving.knative.dev/v1
kind: Service
...
spec:
  template:
    metadata:
       annotations:
            serving.knative.dev/progress-deadline: "60s"
    spec:
        containers:
            - image: ghcr.io/knative/helloworld-go:latest

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4.6. Resolving image tags to digests
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If the Knative Serving controller has access to the container registry, Knative Serving resolves image tags to a digest when you create a revision of a service. This is known as tag-to-digest resolution, and helps to provide consistency for deployments.

4.6.1. Tag-to-digest resolution
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To give the controller access to the container registry on OpenShift Container Platform, you must create a secret and then configure controller custom certificates. You can configure controller custom certificates by modifying the controller-custom-certs spec in the KnativeServing custom resource (CR). The secret must reside in the same namespace as the KnativeServing CR.

If a secret is not included in the KnativeServing CR, this setting defaults to using public key infrastructure (PKI). When using PKI, the cluster-wide certificates are automatically injected into the Knative Serving controller by using the config-service-sa config map. The OpenShift Serverless Operator populates the config-service-sa config map with cluster-wide certificates and mounts the config map as a volume to the controller.

4.6.1.1. Configuring tag-to-digest resolution by using a secret
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If the controller-custom-certs spec uses the Secret type, the secret is mounted as a secret volume. Knative components consume the secret directly, assuming that the secret has the required certificates.

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.
You have installed the OpenShift Serverless Operator and Knative Serving on your cluster.

Procedure

Create a secret:

Example command

$ oc -n knative-serving create secret generic custom-secret --from-file=<secret_name>.crt=<path_to_certificate>

$ oc -n knative-serving create secret generic custom-secret --from-file=<secret_name>.crt=<path_to_certificate>

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Configure the controller-custom-certs spec in the KnativeServing custom resource (CR) to use the Secret type:

Example KnativeServing CR

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  controller-custom-certs:
    name: custom-secret
    type: Secret

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  controller-custom-certs:
    name: custom-secret
    type: Secret

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4.7. Configuring deployment resources
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In Knative Serving, the config-deployment config map contains settings that determine how Kubernetes Deployment resources are configured for Knative services. In OpenShift Serverless Serving, you can configure these settings in the deployment section of your KnativeServing custom resource (CR).

You can use the deployment section to configure the following:

Tag resolution
Runtime environments
Progress deadlines

4.7.1. Skipping tag resolution
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Skipping tag resolution in OpenShift Serverless Serving can speed up deployments by avoiding unnecessary queries to the container registry, reducing latency and dependency on registry availability.

You can configure Serving to skip tag resolution by modifying the registriesSkippingTagResolving setting in your KnativeServing custom resource (CR).

Procedure

In your KnativeServing CR, modify the registriesSkippingTagResolving setting with the list of registries for which tag resoution will be skipped:

Example of configured tag resolution skipping

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    deployment:
      registriesSkippingTagResolving: "registry.example.com, another.registry.com"

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    deployment:
      registriesSkippingTagResolving: "registry.example.com, another.registry.com"

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4.7.2. Configuring selectable RuntimeClassName
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You can configure OpenShift Serverless Serving to set a specific RuntimeClassName resource for Deployments by updating the runtime-class-name setting in your KnativeServing custom resource (CR).

This setting interacts with service labels, applying either the default RuntimeClassName or the one that matches the most labels associated with the service.

Procedure

In your KnativeServing CR, configure the runtime-class-name setting:

Example of configured runtime-class-name setting

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    deployment:
      runtime-class-name: |
        kata: {}
        gvisor:
          selector:
            my-label: selector

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    deployment:
      runtime-class-name: |
        kata: {}
        gvisor:
          selector:
            my-label: selector

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4.7.3. Progress deadline
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By default, services have a progress deadline that defines the time limit for a service to complete its initial startup.

Consider increasing the progress deadline if you encounter any of these conditions in your deployment:

The service image takes a long time to pull due to its size.
The service takes a long time to become READY because of initial cache priming.
The cluster relies on autoscaling to allocate resources for new pods.

If the initial scale is not achieved within the specified time limit, the Knative Autoscaler component scales the revision to 0, and the service enters a terminal Failed state.

4.7.3.1. Configuring the progress deadline
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Configure progress deadline settings to set the maximum time allowed in seconds or minutes for deployment progress before the system reports a Knative Revision failure.

By default, the progress deadline is set to 600 seconds. This value is specified as a Go time.Duration string and must be rounded to the nearest second.

Procedure

Configure progress deadline by modifying your KnativeServing custom resource (CR).

In your KnativeServing CR, set the value of progressDeadline:

Example of progress deadline set to 60 seconds

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    deployment:
      progressDeadline: "60s"

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    deployment:
      progressDeadline: "60s"

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4.8. Configuring Kourier
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Kourier is a lightweight Kubernetes-native Ingress for Knative Serving. Kourier acts as a gateway for Knative, routing HTTP traffic to Knative services.

4.8.1. Accessing the current Envoy bootstrap configuration
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The Envoy proxy component in Kourier handles inbound and outbound HTTP traffic for the Knative services. By default, Kourier contains an Envoy bootstrap configuration in the kourier-bootstrap configuration map in the knative-serving-ingress namespace.

Procedure

To get the current Envoy bootstrap configuration, run the following command:

Example command

oc get cm kourier-bootstrap -n knative-serving-ingress -o yaml

$ oc get cm kourier-bootstrap -n knative-serving-ingress -o yaml

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For example, with the default configuration, the example command produces the output that contains the following excerpts:

Example output

Name:         kourier-bootstrap
Namespace:    knative-serving-ingress
Labels:       app.kubernetes.io/component=net-kourier
              app.kubernetes.io/name=knative-serving
              app.kubernetes.io/version=release-v1.10
              networking.knative.dev/ingress-provider=kourier
              serving.knative.openshift.io/ownerName=knative-serving
              serving.knative.openshift.io/ownerNamespace=knative-serving
Annotations:  manifestival: new

Name:         kourier-bootstrap
Namespace:    knative-serving-ingress
Labels:       app.kubernetes.io/component=net-kourier
              app.kubernetes.io/name=knative-serving
              app.kubernetes.io/version=release-v1.10
              networking.knative.dev/ingress-provider=kourier
              serving.knative.openshift.io/ownerName=knative-serving
              serving.knative.openshift.io/ownerNamespace=knative-serving
Annotations:  manifestival: new

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Example Data output

dynamic_resources:
  ads_config:
    transport_api_version: V3
    api_type: GRPC
    rate_limit_settings: {}
    grpc_services:
    - envoy_grpc: {cluster_name: xds_cluster}
  cds_config:
    resource_api_version: V3
    ads: {}
  lds_config:
    resource_api_version: V3
    ads: {}
node:
  cluster: kourier-knative
  id: 3scale-kourier-gateway
static_resources:
  listeners:
    - name: stats_listener
      address:
        socket_address:
          address: 0.0.0.0
          port_value: 9000
      filter_chains:
        - filters:
            - name: envoy.filters.network.http_connection_manager
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
                stat_prefix: stats_server
                http_filters:
                  - name: envoy.filters.http.router
                    typed_config:
                      "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
                route_config:
                  virtual_hosts:
                    - name: admin_interface
                      domains:
                        - "*"
                      routes:
                        - match:
                            safe_regex:
                              regex: '/(certs|stats(/prometheus)?|server_info|clusters|listeners|ready)?'
                            headers:
                              - name: ':method'
                                string_match:
                                  exact: GET
                          route:
                            cluster: service_stats
  clusters:
    - name: service_stats
      connect_timeout: 0.250s
      type: static
      load_assignment:
        cluster_name: service_stats
        endpoints:
          lb_endpoints:
            endpoint:
              address:
                pipe:
                  path: /tmp/envoy.admin
    - name: xds_cluster
      # This keepalive is recommended by envoy docs.
      # https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol
      typed_extension_protocol_options:
        envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
          "@type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
          explicit_http_config:
            http2_protocol_options:
              connection_keepalive:
                interval: 30s
                timeout: 5s
      connect_timeout: 1s
      load_assignment:
        cluster_name: xds_cluster
        endpoints:
          lb_endpoints:
            endpoint:
              address:
                socket_address:
                  address: "net-kourier-controller.knative-serving-ingress.svc.cluster.local."
                  port_value: 18000
      type: STRICT_DNS
admin:
  access_log:
  - name: envoy.access_loggers.stdout
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
  address:
    pipe:
      path: /tmp/envoy.admin
layered_runtime:
  layers:
    - name: static-layer
      static_layer:
        envoy.reloadable_features.override_request_timeout_by_gateway_timeout: false

dynamic_resources:
  ads_config:
    transport_api_version: V3
    api_type: GRPC
    rate_limit_settings: {}
    grpc_services:
    - envoy_grpc: {cluster_name: xds_cluster}
  cds_config:
    resource_api_version: V3
    ads: {}
  lds_config:
    resource_api_version: V3
    ads: {}
node:
  cluster: kourier-knative
  id: 3scale-kourier-gateway
static_resources:
  listeners:
    - name: stats_listener
      address:
        socket_address:
          address: 0.0.0.0
          port_value: 9000
      filter_chains:
        - filters:
            - name: envoy.filters.network.http_connection_manager
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
                stat_prefix: stats_server
                http_filters:
                  - name: envoy.filters.http.router
                    typed_config:
                      "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
                route_config:
                  virtual_hosts:
                    - name: admin_interface
                      domains:
                        - "*"
                      routes:
                        - match:
                            safe_regex:
                              regex: '/(certs|stats(/prometheus)?|server_info|clusters|listeners|ready)?'
                            headers:
                              - name: ':method'
                                string_match:
                                  exact: GET
                          route:
                            cluster: service_stats
  clusters:
    - name: service_stats
      connect_timeout: 0.250s
      type: static
      load_assignment:
        cluster_name: service_stats
        endpoints:
          lb_endpoints:
            endpoint:
              address:
                pipe:
                  path: /tmp/envoy.admin
    - name: xds_cluster
      # This keepalive is recommended by envoy docs.
      # https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol
      typed_extension_protocol_options:
        envoy.extensions.upstreams.http.v3.HttpProtocolOptions:
          "@type": type.googleapis.com/envoy.extensions.upstreams.http.v3.HttpProtocolOptions
          explicit_http_config:
            http2_protocol_options:
              connection_keepalive:
                interval: 30s
                timeout: 5s
      connect_timeout: 1s
      load_assignment:
        cluster_name: xds_cluster
        endpoints:
          lb_endpoints:
            endpoint:
              address:
                socket_address:
                  address: "net-kourier-controller.knative-serving-ingress.svc.cluster.local."
                  port_value: 18000
      type: STRICT_DNS
admin:
  access_log:
  - name: envoy.access_loggers.stdout
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
  address:
    pipe:
      path: /tmp/envoy.admin
layered_runtime:
  layers:
    - name: static-layer
      static_layer:
        envoy.reloadable_features.override_request_timeout_by_gateway_timeout: false

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Example BinaryData output

Events:  <none>

Events:  <none>

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4.8.2. Customizing kourier-bootstrap for Kourier getaways
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The Envoy proxy component in Kourier handles inbound and outbound HTTP traffic for the Knative services. By default, Kourier contains an Envoy bootstrap configuration in the kourier-bootstrap configuration map in the knative-serving-ingress namespace. You can change this configuration map to a custom one.

Prerequisites

You have installed the OpenShift Serverless Operator and Knative Serving.
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.

Procedure

Specify a custom bootstrapping configuration map by changing the spec.ingress.kourier.bootstrap-configmap field in the KnativeServing custom resource (CR):

Example KnativeServing CR

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  config:
    network:
      ingress-class: kourier.ingress.networking.knative.dev
  ingress:
    kourier:
      bootstrap-configmap: my-configmap
      enabled: true
# ...

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  config:
    network:
      ingress-class: kourier.ingress.networking.knative.dev
  ingress:
    kourier:
      bootstrap-configmap: my-configmap
      enabled: true
# ...

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4.8.3. Enabling administrator interface access
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You can change the envoy bootstrap configuration to enable access to the administrator interface.

Important

This procedure assumes sufficient knowledge of Knative, as changing envoy bootstrap configuration might result in Knative failure. Red Hat does not support custom configurations that are not tested or shipped with the product.

Prerequisites

You have installed the OpenShift Serverless Operator and Knative Serving.
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.

Procedure

To enable administrator interface access, locate this configuration in your bootstrapping configuration map:
```
pipe:
  path: /tmp/envoy.admin
```
```
pipe:
  path: /tmp/envoy.admin
```
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Substitute it with the following configuration:
```
socket_address: 
  address: 127.0.0.1
  port_value: 9901
```
```
socket_address: 
```
1
```
  address: 127.0.0.1
  port_value: 9901
```
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1
This configuration enables access to the Envoy admin interface on the loopback address (127.0.0.1) and port 9901.

Apply the socket_address configuration in the service_stats cluster configuration and in the admin configuration:

The first is in the service_stats cluster configuration:

clusters:
  - name: service_stats
    connect_timeout: 0.250s
    type: static
    load_assignment:
      cluster_name: service_stats
      endpoints:
        lb_endpoints:
          endpoint:
            address:
              socket_address:
                address: 127.0.0.1
                port_value: 9901

clusters:
  - name: service_stats
    connect_timeout: 0.250s
    type: static
    load_assignment:
      cluster_name: service_stats
      endpoints:
        lb_endpoints:
          endpoint:
            address:
              socket_address:
                address: 127.0.0.1
                port_value: 9901

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The second is in the admin configuration:

admin:
  access_log:
    - name: envoy.access_loggers.stdout
      typed_config:
        "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
  address:
    socket_address:
      address: 127.0.0.1
      port_value: 9901

admin:
  access_log:
    - name: envoy.access_loggers.stdout
      typed_config:
        "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
  address:
    socket_address:
      address: 127.0.0.1
      port_value: 9901

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4.9. Restrictive network policies
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4.9.1. Clusters with restrictive network policies
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If you are using a cluster that multiple users have access to, your cluster might use network policies to control which pods, services, and namespaces can communicate with each other over the network. If your cluster uses restrictive network policies, it is possible that Knative system pods are not able to access your Knative application. For example, if your namespace has the following network policy, which denies all requests, Knative system pods cannot access your Knative application:

Example NetworkPolicy object that denies all requests to the namespace

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: deny-by-default
  namespace: example-namespace
spec:
  podSelector:
  ingress: []

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: deny-by-default
  namespace: example-namespace
spec:
  podSelector:
  ingress: []

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4.9.2. Enabling communication with Knative applications on a cluster with restrictive network policies
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To allow access to your applications from Knative system pods, you must add a label to each of the Knative system namespaces, and then create a NetworkPolicy object in your application namespace that allows access to the namespace for other namespaces that have this label.

Important

A network policy that denies requests to non-Knative services on your cluster still prevents access to these services. However, by allowing access from Knative system namespaces to your Knative application, you are allowing access to your Knative application from all namespaces in the cluster.

If you do not want to allow access to your Knative application from all namespaces on the cluster, you might want to use JSON Web Token authentication for Knative services instead. JSON Web Token authentication for Knative services requires Service Mesh.

Prerequisites

Install the OpenShift CLI (oc).
OpenShift Serverless Operator and Knative Serving are installed on your cluster.

Procedure

Add the knative.openshift.io/system-namespace=true label to each Knative system namespace that requires access to your application:

Label the knative-serving namespace:

oc label namespace knative-serving knative.openshift.io/system-namespace=true

$ oc label namespace knative-serving knative.openshift.io/system-namespace=true

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Label the knative-serving-ingress namespace:

oc label namespace knative-serving-ingress knative.openshift.io/system-namespace=true

$ oc label namespace knative-serving-ingress knative.openshift.io/system-namespace=true

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Label the knative-eventing namespace:

oc label namespace knative-eventing knative.openshift.io/system-namespace=true

$ oc label namespace knative-eventing knative.openshift.io/system-namespace=true

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Label the knative-kafka namespace:

oc label namespace knative-kafka knative.openshift.io/system-namespace=true

$ oc label namespace knative-kafka knative.openshift.io/system-namespace=true

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Create a NetworkPolicy object in your application namespace to allow access from namespaces with the knative.openshift.io/system-namespace label:

Example NetworkPolicy object

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: <network_policy_name> 
  namespace: <namespace> 
spec:
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          knative.openshift.io/system-namespace: "true"
  podSelector: {}
  policyTypes:
  - Ingress

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: <network_policy_name>

1


  namespace: <namespace>

2


spec:
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          knative.openshift.io/system-namespace: "true"
  podSelector: {}
  policyTypes:
  - Ingress

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1: Provide a name for your network policy.
2: The namespace where your application exists.

4.10. Configuring revision timeouts
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You can configure timeout durations for revisions globally or individually to control the time spent on requests.

4.10.1. Configuring revision timeout
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You can configure the default number of seconds for the revision timeout based on the request.

Prerequisites

You have installed the OpenShift Serverless Operator and Knative Serving.
You have cluster administrator permissions on OpenShift Container Platform, or cluster or dedicated administrator permissions on Red Hat OpenShift Service on AWS or OpenShift Dedicated.

Procedure

Choose the appropriate method to configure the revision timeout:

To configure the revision timeout globally, set the revision-timeout-seconds field in the KnativeServing custom resource (CR):

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  config:
    defaults:
      revision-timeout-seconds: "300"

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  config:
    defaults:
      revision-timeout-seconds: "300"

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To configure the timeout per revision by setting the timeoutSeconds field in your service definition:

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  namespace: my-ns
spec:
  template:
    spec:
      timeoutSeconds: 300
      containers:
      - image: ghcr.io/knative/helloworld-go:latest

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  namespace: my-ns
spec:
  template:
    spec:
      timeoutSeconds: 300
      containers:
      - image: ghcr.io/knative/helloworld-go:latest

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4.10.2. Configuring maximum revision timeout
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By seting the maximum revision timeout, you can ensure that no revision can exceed a specific limit.

Prerequisites

You have installed the OpenShift Serverless Operator and Knative Serving.
You have cluster administrator permissions on OpenShift Container Platform, or cluster or dedicated administrator permissions on Red Hat OpenShift Service on AWS or OpenShift Dedicated.

Procedure

To configure the maximum revision timeout, set the max-revision-timeout-seconds field in the KnativeServing custom resource (CR):

If this value is increased, the activator `terminationGracePeriodSeconds` should also be increased to prevent in-flight requests being disrupted.

If this value is increased, the activator `terminationGracePeriodSeconds` should also be increased to prevent in-flight requests being disrupted.

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apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  config:
    defaults:
      max-revision-timeout-seconds: "600"

apiVersion: operator.knative.dev/v1beta1
kind: KnativeServing
metadata:
  name: knative-serving
  namespace: knative-serving
spec:
  config:
    defaults:
      max-revision-timeout-seconds: "600"

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4.1. Multi-container support for ServingCopy linkLink copied to clipboard!

4.1.1. Configuring a multi-container serviceCopy linkLink copied to clipboard!

4.1.2. Probing a multi-container serviceCopy linkLink copied to clipboard!

4.1.2.1. Additional resourcesCopy linkLink copied to clipboard!

4.2. EmptyDir volumesCopy linkLink copied to clipboard!

4.2.1. Configuring the EmptyDir extensionCopy linkLink copied to clipboard!

4.3. Persistent Volume Claims for ServingCopy linkLink copied to clipboard!

4.3.1. Enabling PVC supportCopy linkLink copied to clipboard!

4.4. Init containersCopy linkLink copied to clipboard!

4.4.1. Enabling init containersCopy linkLink copied to clipboard!

4.5. Startup probesCopy linkLink copied to clipboard!

4.5.1. Progress deadlineCopy linkLink copied to clipboard!

4.5.2. Configuring startup probingCopy linkLink copied to clipboard!

4.5.3. Configuring the progress deadlineCopy linkLink copied to clipboard!

4.6. Resolving image tags to digestsCopy linkLink copied to clipboard!

4.6.1. Tag-to-digest resolutionCopy linkLink copied to clipboard!

4.6.1.1. Configuring tag-to-digest resolution by using a secretCopy linkLink copied to clipboard!

4.7. Configuring deployment resourcesCopy linkLink copied to clipboard!

4.7.1. Skipping tag resolutionCopy linkLink copied to clipboard!

4.7.2. Configuring selectable RuntimeClassNameCopy linkLink copied to clipboard!

4.7.3. Progress deadlineCopy linkLink copied to clipboard!

4.7.3.1. Configuring the progress deadlineCopy linkLink copied to clipboard!

4.8. Configuring KourierCopy linkLink copied to clipboard!

4.8.1. Accessing the current Envoy bootstrap configurationCopy linkLink copied to clipboard!

4.8.2. Customizing kourier-bootstrap for Kourier getawaysCopy linkLink copied to clipboard!

4.8.3. Enabling administrator interface accessCopy linkLink copied to clipboard!

4.9. Restrictive network policiesCopy linkLink copied to clipboard!

4.9.1. Clusters with restrictive network policiesCopy linkLink copied to clipboard!

4.9.2. Enabling communication with Knative applications on a cluster with restrictive network policiesCopy linkLink copied to clipboard!

4.10. Configuring revision timeoutsCopy linkLink copied to clipboard!

4.10.1. Configuring revision timeoutCopy linkLink copied to clipboard!

4.10.2. Configuring maximum revision timeoutCopy linkLink copied to clipboard!

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4.1. Multi-container support for Serving
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4.1.1. Configuring a multi-container service
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4.1.2. Probing a multi-container service
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4.1.2.1. Additional resources
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4.2. EmptyDir volumes
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4.2.1. Configuring the EmptyDir extension
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4.3. Persistent Volume Claims for Serving
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4.3.1. Enabling PVC support
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4.4. Init containers
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4.4.1. Enabling init containers
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4.5. Startup probes
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4.5.1. Progress deadline
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4.5.2. Configuring startup probing
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4.5.3. Configuring the progress deadline
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4.6. Resolving image tags to digests
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4.6.1. Tag-to-digest resolution
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4.6.1.1. Configuring tag-to-digest resolution by using a secret
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4.7. Configuring deployment resources
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4.7.1. Skipping tag resolution
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4.7.2. Configuring selectable RuntimeClassName
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4.7.3. Progress deadline
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4.7.3.1. Configuring the progress deadline
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4.8. Configuring Kourier
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4.8.1. Accessing the current Envoy bootstrap configuration
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4.8.2. Customizing kourier-bootstrap for Kourier getaways
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4.8.3. Enabling administrator interface access
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4.9. Restrictive network policies
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4.9.1. Clusters with restrictive network policies
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4.9.2. Enabling communication with Knative applications on a cluster with restrictive network policies
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4.10. Configuring revision timeouts
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4.10.1. Configuring revision timeout
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4.10.2. Configuring maximum revision timeout
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