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Knative CLI

Red Hat OpenShift Serverless 1.35

Overview of CLI commands for Knative Functions, Serving, and Eventing

Red Hat OpenShift Documentation Team

Abstract

This document provides an overview of the CLI commands available for Knative Functions, Serving, and Eventing. It also provides information about configuring the Knative CLI and on using plugins.

Chapter 1. Knative Serving CLI commands
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1.1. kn service commands
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You can use the following commands to create and manage Knative services.

Using the Knative (kn) CLI to create serverless applications provides a more streamlined and intuitive user interface over modifying YAML files directly. You can use the kn service create command to create a basic serverless application.

Prerequisites

  • OpenShift Serverless Operator and Knative Serving are installed on your 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

  • Create a Knative service: 

    $ kn service create <service-name> --image <image> --tag <tag-value>
    Copy to Clipboard Toggle word wrap

    Where:

    • --image is the URI of the image for the application.

    • --tag is an optional flag that can be used to add a tag to the initial revision that is created with the service.

      Example command

      $ kn service create showcase \
    --image quay.io/openshift-knative/showcase
      Copy to Clipboard Toggle word wrap

      Example output

      Creating service 'showcase' in namespace 'default':

  0.271s The Route is still working to reflect the latest desired specification.
  0.580s Configuration "showcase" is waiting for a Revision to become ready.
  3.857s ...
  3.861s Ingress has not yet been reconciled.
  4.270s Ready to serve.

Service 'showcase' created with latest revision 'showcase-00001' and URL:
http://showcase-default.apps-crc.testing
      Copy to Clipboard Toggle word wrap

You can use the kn service update command for interactive sessions on the command line as you build up a service incrementally. In contrast to the kn service apply command, when using the kn service update command you only have to specify the changes that you want to update, rather than the full configuration for the Knative service.

Example commands

  • Update a service by adding a new environment variable: 

    $ kn service update <service_name> --env <key>=<value>
    Copy to Clipboard Toggle word wrap

  • Update a service by adding a new port: 

    $ kn service update <service_name> --port 80
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  • Update a service by adding new request and limit parameters: 

    $ kn service update <service_name> --request cpu=500m --limit memory=1024Mi --limit cpu=1000m
    Copy to Clipboard Toggle word wrap

  • Assign the latest tag to a revision: 

    $ kn service update <service_name> --tag <revision_name>=latest
    Copy to Clipboard Toggle word wrap

  • Update a tag from testing to staging for the latest READY revision of a service: 

    $ kn service update <service_name> --untag testing --tag @latest=staging
    Copy to Clipboard Toggle word wrap

  • Add the test tag to a revision that receives 10% of traffic, and send the rest of the traffic to the latest READY revision of a service: 

    $ kn service update <service_name> --tag <revision_name>=test --traffic test=10,@latest=90
    Copy to Clipboard Toggle word wrap

1.1.3. Applying service declarations
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You can declaratively configure a Knative service by using the kn service apply command. If the service does not exist it is created, otherwise the existing service is updated with the options that have been changed.

The kn service apply command is especially useful for shell scripts or in a continuous integration pipeline, where users typically want to fully specify the state of the service in a single command to declare the target state.

When using kn service apply you must provide the full configuration for the Knative service. This is different from the kn service update command, which only requires you to specify in the command the options that you want to update.

Example commands

  • Create a service: 

    $ kn service apply <service_name> --image <image>
    Copy to Clipboard Toggle word wrap

  • Add an environment variable to a service: 

    $ kn service apply <service_name> --image <image> --env <key>=<value>
    Copy to Clipboard Toggle word wrap

  • Read the service declaration from a JSON or YAML file: 

    $ kn service apply <service_name> -f <filename>
    Copy to Clipboard Toggle word wrap

You can describe a Knative service by using the kn service describe command.

Example commands

  • Describe a service: 

    $ kn service describe --verbose <service_name>
    Copy to Clipboard Toggle word wrap

    The --verbose flag is optional but can be included to provide a more detailed description. The difference between a regular and verbose output is shown in the following examples:

    Example output without --verbose flag

    Name:       showcase
Namespace:  default
Age:        2m
URL:        http://showcase-default.apps.ocp.example.com

Revisions:
  100%  @latest (showcase-00001) [1] (2m)
        Image:  quay.io/openshift-knative/showcase (pinned to aaea76)

Conditions:
  OK TYPE                   AGE REASON
  ++ Ready                   1m
  ++ ConfigurationsReady     1m
  ++ RoutesReady             1m
    Copy to Clipboard Toggle word wrap

    Example output with --verbose flag

    Name:         showcase
Namespace:    default
Annotations:  serving.knative.dev/creator=system:admin
              serving.knative.dev/lastModifier=system:admin
Age:          3m
URL:          http://showcase-default.apps.ocp.example.com
Cluster:      http://showcase.default.svc.cluster.local

Revisions:
  100%  @latest (showcase-00001) [1] (3m)
        Image:  quay.io/openshift-knative/showcase (pinned to aaea76)
        Env:    GREET=Bonjour

Conditions:
  OK TYPE                   AGE REASON
  ++ Ready                   3m
  ++ ConfigurationsReady     3m
  ++ RoutesReady             3m
    Copy to Clipboard Toggle word wrap

  • Describe a service in YAML format: 

    $ kn service describe <service_name> -o yaml
    Copy to Clipboard Toggle word wrap

  • Describe a service in JSON format: 

    $ kn service describe <service_name> -o json
    Copy to Clipboard Toggle word wrap

  • Print the service URL only: 

    $ kn service describe <service_name> -o url
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1.2. kn service commands in offline mode
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1.2.1. About the Knative CLI offline mode
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When you execute kn service commands, the changes immediately propagate to the cluster. However, as an alternative, you can execute kn service commands in offline mode. When you create a service in offline mode, no changes happen on the cluster, and instead the service descriptor file is created on your local machine.

Important

The offline mode of the Knative CLI is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

After the descriptor file is created, you can manually modify it and track it in a version control system. You can also propagate changes to the cluster by using the kn service create -f, kn service apply -f, or oc apply -f commands on the descriptor files.

The offline mode has several uses:

  • You can manually modify the descriptor file before using it to make changes on the cluster.
  • You can locally track the descriptor file of a service in a version control system. This enables you to reuse the descriptor file in places other than the target cluster, for example in continuous integration (CI) pipelines, development environments, or demos.
  • You can examine the created descriptor files to learn about Knative services. In particular, you can see how the resulting service is influenced by the different arguments passed to the kn command.

The offline mode has its advantages: it is fast, and does not require a connection to the cluster. However, offline mode lacks server-side validation. Consequently, you cannot, for example, verify that the service name is unique or that the specified image can be pulled.

1.2.2. Creating a service using offline mode
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You can execute kn service commands in offline mode, so that no changes happen on the cluster, and instead the service descriptor file is created on your local machine. After the descriptor file is created, you can modify the file before propagating changes to the cluster.

Important

The offline mode of the Knative CLI is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Prerequisites

  • OpenShift Serverless Operator and Knative Serving are installed on your cluster.
  • You have installed the Knative (kn) CLI.

Procedure

  1. In offline mode, create a local Knative service descriptor file: 

    $ kn service create showcase \
    --image quay.io/openshift-knative/showcase \
    --target ./ \
    --namespace test
    Copy to Clipboard Toggle word wrap

    Example output

    Service 'showcase' created in namespace 'test'.
    Copy to Clipboard Toggle word wrap

    • The --target ./ flag enables offline mode and specifies ./ as the directory for storing the new directory tree.

      If you do not specify an existing directory, but use a filename, such as --target my-service.yaml, then no directory tree is created. Instead, only the service descriptor file my-service.yaml is created in the current directory.

      The filename can have the .yaml, .yml, or .json extension. Choosing .json creates the service descriptor file in the JSON format.

    • The --namespace test option places the new service in the test namespace.

      If you do not use --namespace, and you are logged in to an OpenShift Container Platform cluster, the descriptor file is created in the current namespace. Otherwise, the descriptor file is created in the default namespace.

  2. Examine the created directory structure: 

    $ tree ./
    Copy to Clipboard Toggle word wrap

    Example output

    ./
└── test
    └── ksvc
        └── showcase.yaml

2 directories, 1 file
    Copy to Clipboard Toggle word wrap

    • The current ./ directory specified with --target contains the new test/ directory that is named after the specified namespace.
    • The test/ directory contains the ksvc directory, named after the resource type.
    • The ksvc directory contains the descriptor file showcase.yaml, named according to the specified service name.

  3. Examine the generated service descriptor file: 

    $ cat test/ksvc/showcase.yaml
    Copy to Clipboard Toggle word wrap

    Example output

    apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  creationTimestamp: null
  name: showcase
  namespace: test
spec:
  template:
    metadata:
      annotations:
        client.knative.dev/user-image: quay.io/openshift-knative/showcase
      creationTimestamp: null
    spec:
      containers:
      - image: quay.io/openshift-knative/showcase
        name: ""
        resources: {}
status: {}
    Copy to Clipboard Toggle word wrap

  4. List information about the new service: 

    $ kn service describe showcase --target ./ --namespace test
    Copy to Clipboard Toggle word wrap

    Example output

    Name:       showcase
Namespace:  test
Age:
URL:

Revisions:

Conditions:
  OK TYPE    AGE REASON
    Copy to Clipboard Toggle word wrap

    • The --target ./ option specifies the root directory for the directory structure containing namespace subdirectories.

      Alternatively, you can directly specify a YAML or JSON filename with the --target option. The accepted file extensions are .yaml, .yml, and .json.

    • The --namespace option specifies the namespace, which communicates to kn the subdirectory that contains the necessary service descriptor file.

      If you do not use --namespace, and you are logged in to an OpenShift Container Platform cluster, kn searches for the service in the subdirectory that is named after the current namespace. Otherwise, kn searches in the default/ subdirectory.

  5. Use the service descriptor file to create the service on the cluster: 

    $ kn service create -f test/ksvc/showcase.yaml
    Copy to Clipboard Toggle word wrap

    Example output

    Creating service 'showcase' in namespace 'test':

  0.058s The Route is still working to reflect the latest desired specification.
  0.098s ...
  0.168s Configuration "showcase" is waiting for a Revision to become ready.
 23.377s ...
 23.419s Ingress has not yet been reconciled.
 23.534s Waiting for load balancer to be ready
 23.723s Ready to serve.

Service 'showcase' created to latest revision 'showcase-00001' is available at URL:
http://showcase-test.apps.example.com
    Copy to Clipboard Toggle word wrap

1.3. kn container commands
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You can use the following commands to create and manage multiple containers in a Knative service spec.

1.3.1. Knative client multi-container support
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You can use the kn container add command to print YAML container spec to standard output. This command is useful for multi-container use cases because it can be used along with other standard kn flags to create definitions.

The kn container add command accepts all container-related flags that are supported for use with the kn service create command. The kn container add command can also be chained by using UNIX pipes (|) to create multiple container definitions at once.

Example commands

  • Add a container from an image and print it to standard output: 

    $ kn container add <container_name> --image <image_uri>
    Copy to Clipboard Toggle word wrap

    Example command

    $ kn container add sidecar --image docker.io/example/sidecar
    Copy to Clipboard Toggle word wrap

    Example output

    containers:
- image: docker.io/example/sidecar
  name: sidecar
  resources: {}
    Copy to Clipboard Toggle word wrap

  • Chain two kn container add commands together, and then pass them to a kn service create command to create a Knative service with two containers: 

    $ kn container add <first_container_name> --image <image_uri> | \
kn container add <second_container_name> --image <image_uri> | \
kn service create <service_name> --image <image_uri> --extra-containers -
    Copy to Clipboard Toggle word wrap

    --extra-containers - specifies a special case where kn reads the pipe input instead of a YAML file.

    Example command

    $ kn container add sidecar --image docker.io/example/sidecar:first | \
kn container add second --image docker.io/example/sidecar:second | \
kn service create my-service --image docker.io/example/my-app:latest --extra-containers -
    Copy to Clipboard Toggle word wrap

    The --extra-containers flag can also accept a path to a YAML file: 

    $ kn service create <service_name> --image <image_uri> --extra-containers <filename>
    Copy to Clipboard Toggle word wrap

    Example command

    $ kn service create my-service --image docker.io/example/my-app:latest --extra-containers my-extra-containers.yaml
    Copy to Clipboard Toggle word wrap

1.4. kn domain commands
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You can use the following commands to create and manage domain mappings.

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.

    Note

    Your 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>
    Copy to Clipboard Toggle word wrap

    Example command

    $ kn domain create example.com --ref showcase
    Copy to Clipboard Toggle word wrap

    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>
    Copy to Clipboard Toggle word wrap

    Example command

    $ kn domain create example.com --ref ksvc:showcase:example-namespace
    Copy to Clipboard Toggle word wrap

  • Map a domain to a Knative route: 

    $ kn domain create <domain_mapping_name> --ref <kroute:route_name>
    Copy to Clipboard Toggle word wrap

    Example command

    $ kn domain create example.com --ref kroute:example-route
    Copy to Clipboard Toggle word wrap

After you have created a DomainMapping custom resource (CR), you can list existing CRs, view information about an existing CR, update CRs, or delete CRs by using the Knative (kn) CLI.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on your cluster.
  • You have created at least one DomainMapping CR.
  • You have installed the Knative (kn) CLI tool.
  • 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

  • List existing DomainMapping CRs: 

    $ kn domain list -n <domain_mapping_namespace>
    Copy to Clipboard Toggle word wrap

  • View details of an existing DomainMapping CR: 

    $ kn domain describe <domain_mapping_name>
    Copy to Clipboard Toggle word wrap

  • Update a DomainMapping CR to point to a new target: 

    $ kn domain update --ref <target>
    Copy to Clipboard Toggle word wrap

  • Delete a DomainMapping CR: 

    $ kn domain delete <domain_mapping_name>
    Copy to Clipboard Toggle word wrap

Chapter 2. Configuring the Knative CLI
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You can customize your Knative (kn) CLI setup by creating a config.yaml configuration file. You can provide this configuration by using the --config flag, otherwise the configuration is picked up from a default location. The default configuration location conforms to the XDG Base Directory Specification, and is different for UNIX systems and Windows systems.

For UNIX systems:

  • If the XDG_CONFIG_HOME environment variable is set, the default configuration location that the Knative (kn) CLI looks for is $XDG_CONFIG_HOME/kn.
  • If the XDG_CONFIG_HOME environment variable is not set, the Knative (kn) CLI looks for the configuration in the home directory of the user at $HOME/.config/kn/config.yaml.

For Windows systems, the default Knative (kn) CLI configuration location is %APPDATA%\kn.

Example configuration file

plugins:
  path-lookup: true
1 

  directory: ~/.config/kn/plugins
2 

eventing:
  sink-mappings:
3 

  - prefix: svc
4 

    group: core
5 

    version: v1
6 

    resource: services
7
Copy to Clipboard Toggle word wrap

1
Specifies whether the Knative (kn) CLI should look for plugins in the PATH environment variable. This is a boolean configuration option. The default value is false.
2
Specifies the directory where the Knative (kn) CLI looks for plugins. The default path depends on the operating system, as described previously. This can be any directory that is visible to the user.
3
The sink-mappings spec defines the Kubernetes addressable resource that is used when you use the --sink flag with a Knative (kn) CLI command.
4
The prefix you want to use to describe your sink. svc for a service, channel, and broker are predefined prefixes for the Knative (kn) CLI.
5
The API group of the Kubernetes resource.
6
The version of the Kubernetes resource.
7
The plural name of the Kubernetes resource type. For example, services or brokers.

Chapter 3. Knative CLI plugins
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The Knative (kn) CLI supports the use of plugins, which enable you to extend the functionality of your kn installation by adding custom commands and other shared commands that are not part of the core distribution. Knative (kn) CLI plugins are used in the same way as the main kn functionality.

Currently, Red Hat supports the kn-source-kafka plugin and the kn-event plugin.

Important

The kn-event plugin is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

3.1. Building events by using the kn-event plugin
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You can use the builder-like interface of the kn event build command to build an event. You can then send that event at a later time or use it in another context.

Prerequisites

  • You have installed the Knative (kn) CLI.

Procedure

  • Build an event: 

    $ kn event build --field <field-name>=<value> --type <type-name> --id <id> --output <format>
    Copy to Clipboard Toggle word wrap

    where:

    • The --field flag adds data to the event as a field-value pair. You can use it multiple times.
    • The --type flag enables you to specify a string that designates the type of the event.
    • The --id flag specifies the ID of the event.

    • You can use the json or yaml arguments with the --output flag to change the output format of the event.

      All of these flags are optional.

      Building a simple event

      $ kn event build -o yaml
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      Resultant event in the YAML format

      data: {}
datacontenttype: application/json
id: 81a402a2-9c29-4c27-b8ed-246a253c9e58
source: kn-event/v0.4.0
specversion: "1.0"
time: "2021-10-15T10:42:57.713226203Z"
type: dev.knative.cli.plugin.event.generic
      Copy to Clipboard Toggle word wrap

      Building a sample transaction event

      $ kn event build \
    --field operation.type=local-wire-transfer \
    --field operation.amount=2345.40 \
    --field operation.from=87656231 \
    --field operation.to=2344121 \
    --field automated=true \
    --field signature='FGzCPLvYWdEgsdpb3qXkaVp7Da0=' \
    --type org.example.bank.bar \
    --id $(head -c 10 < /dev/urandom | base64 -w 0) \
    --output json
      Copy to Clipboard Toggle word wrap

      Resultant event in the JSON format

      {
  "specversion": "1.0",
  "id": "RjtL8UH66X+UJg==",
  "source": "kn-event/v0.4.0",
  "type": "org.example.bank.bar",
  "datacontenttype": "application/json",
  "time": "2021-10-15T10:43:23.113187943Z",
  "data": {
    "automated": true,
    "operation": {
      "amount": "2345.40",
      "from": 87656231,
      "to": 2344121,
      "type": "local-wire-transfer"
    },
    "signature": "FGzCPLvYWdEgsdpb3qXkaVp7Da0="
  }
}
      Copy to Clipboard Toggle word wrap

3.2. Sending events by using the kn-event plugin
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You can use the kn event send command to send an event. The events can be sent either to publicly available addresses or to addressable resources inside a cluster, such as Kubernetes services, as well as Knative services, brokers, and channels. The command uses the same builder-like interface as the kn event build command.

Prerequisites

  • You have installed the Knative (kn) CLI.

Procedure

  • Send an event: 

    $ kn event send --field <field-name>=<value> --type <type-name> --id <id> --to-url <url> --to <cluster-resource> --namespace <namespace>
    Copy to Clipboard Toggle word wrap

    where:

    • The --field flag adds data to the event as a field-value pair. You can use it multiple times.
    • The --type flag enables you to specify a string that designates the type of the event.
    • The --id flag specifies the ID of the event.
    • If you are sending the event to a publicly accessible destination, specify the URL using the --to-url flag.

    • If you are sending the event to an in-cluster Kubernetes resource, specify the destination using the --to flag.

      • Specify the Kubernetes resource using the <Kind>:<ApiVersion>:<name> format.

    • The --namespace flag specifies the namespace. If omitted, the namespace is taken from the current context.

      All of these flags are optional, except for the destination specification, for which you need to use either --to-url or --to.

      The following example shows sending an event to a URL:

      Example command

      $ kn event send \
    --field player.id=6354aa60-ddb1-452e-8c13-24893667de20 \
    --field player.game=2345 \
    --field points=456 \
    --type org.example.gaming.foo \
    --to-url http://ce-api.foo.example.com/
      Copy to Clipboard Toggle word wrap

      The following example shows sending an event to an in-cluster resource:

      Example command

      $ kn event send \
    --type org.example.kn.ping \
    --id $(uuidgen) \
    --field event.type=test \
    --field event.data=98765 \
    --to Service:serving.knative.dev/v1:event-display
      Copy to Clipboard Toggle word wrap

Chapter 4. Knative Eventing CLI commands
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4.1. kn source commands
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You can use the following commands to list, create, and manage Knative event sources.

You can list event source types that can be created and used on your cluster by using the kn source list-types CLI command.

Prerequisites

  • The OpenShift Serverless Operator and Knative Eventing are installed on the cluster.
  • You have installed the Knative (kn) CLI.

Procedure

  1. List the available event source types in the terminal: 

    $ kn source list-types
    Copy to Clipboard Toggle word wrap

    Example output

    TYPE              NAME                                            DESCRIPTION
ApiServerSource   apiserversources.sources.knative.dev            Watch and send Kubernetes API events to a sink
PingSource        pingsources.sources.knative.dev                 Periodically send ping events to a sink
SinkBinding       sinkbindings.sources.knative.dev                Binding for connecting a PodSpecable to a sink
    Copy to Clipboard Toggle word wrap

  2. Optional: On OpenShift Container Platform, you can also list the available event source types in YAML format: 

    $ kn source list-types -o yaml
    Copy to Clipboard Toggle word wrap

4.1.2. Knative CLI sink flag
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When you create an event source by using the Knative (kn) CLI, you can specify a sink where events are sent to from that resource by using the --sink flag. The sink can be any addressable or callable resource that can receive incoming events from other resources.

The following example creates a sink binding that uses a service, http://event-display.svc.cluster.local, as the sink:

Example command using the sink flag

$ kn source binding create bind-heartbeat \
  --namespace sinkbinding-example \
  --subject "Job:batch/v1:app=heartbeat-cron" \
  --sink http://event-display.svc.cluster.local \
1 

  --ce-override "sink=bound"
Copy to Clipboard Toggle word wrap

1
svc in http://event-display.svc.cluster.local determines that the sink is a Knative service. Other default sink prefixes include channel, and broker.

You can use the kn source container commands to create and manage container sources by using the Knative (kn) CLI. Using the Knative CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Create a container source

$ kn source container create <container_source_name> --image <image_uri> --sink <sink>
Copy to Clipboard Toggle word wrap

Delete a container source

$ kn source container delete <container_source_name>
Copy to Clipboard Toggle word wrap

Describe a container source

$ kn source container describe <container_source_name>
Copy to Clipboard Toggle word wrap

List existing container sources

$ kn source container list
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List existing container sources in YAML format

$ kn source container list -o yaml
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Update a container source

This command updates the image URI for an existing container source: 

$ kn source container update <container_source_name> --image <image_uri>
Copy to Clipboard Toggle word wrap

You can use the kn source apiserver create command to create an API server source by using the kn CLI. Using the kn CLI to create an API server source provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator and Knative Eventing are installed on the cluster.
  • 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 installed the OpenShift CLI (oc).
  • You have installed the Knative (kn) CLI.
Procedure

If you want to re-use an existing service account, you can modify your existing ServiceAccount resource to include the required permissions instead of creating a new resource.

  1. Create a service account, role, and role binding for the event source as a YAML file: 

    apiVersion: v1
kind: ServiceAccount
metadata:
  name: events-sa
  namespace: default
    1 
    

---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: event-watcher
  namespace: default
    2 
    
rules:
  - apiGroups:
      - ""
    resources:
      - events
    verbs:
      - get
      - list
      - watch

---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: k8s-ra-event-watcher
  namespace: default
    3 
    
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: event-watcher
subjects:
  - kind: ServiceAccount
    name: events-sa
    namespace: default
    4
    Copy to Clipboard Toggle word wrap
    1 2 3 4
    Change this namespace to the namespace that you have selected for installing the event source.

  2. Apply the YAML file: 

    $ oc apply -f <filename>
    Copy to Clipboard Toggle word wrap

  3. Create an API server source that has an event sink. In the following example, the sink is a broker: 

    $ kn source apiserver create <event_source_name> --sink broker:<broker_name> --resource "event:v1" --service-account <service_account_name> --mode Resource
    Copy to Clipboard Toggle word wrap

  4. To check that the API server source is set up correctly, create a Knative service that dumps incoming messages to its log: 

    $ kn service create event-display --image quay.io/openshift-knative/showcase
    Copy to Clipboard Toggle word wrap

  5. If you used a broker as an event sink, create a trigger to filter events from the default broker to the service: 

    $ kn trigger create <trigger_name> --sink ksvc:event-display
    Copy to Clipboard Toggle word wrap

  6. Create events by launching a pod in the default namespace: 

    $ oc create deployment event-origin --image quay.io/openshift-knative/showcase
    Copy to Clipboard Toggle word wrap

  7. Check that the controller is mapped correctly by inspecting the output generated by the following command: 

    $ kn source apiserver describe <source_name>
    Copy to Clipboard Toggle word wrap

    Example output

    Name:                mysource
Namespace:           default
Annotations:         sources.knative.dev/creator=developer, sources.knative.dev/lastModifier=developer
Age:                 3m
ServiceAccountName:  events-sa
Mode:                Resource
Sink:
  Name:       default
  Namespace:  default
  Kind:       Broker (eventing.knative.dev/v1)
Resources:
  Kind:        event (v1)
  Controller:  false
Conditions:
  OK TYPE                     AGE REASON
  ++ Ready                     3m
  ++ Deployed                  3m
  ++ SinkProvided              3m
  ++ SufficientPermissions     3m
  ++ EventTypesProvided        3m
    Copy to Clipboard Toggle word wrap

Verification

To verify that the Kubernetes events were sent to Knative, look at the event-display logs or use web browser to see the events.

  • To view the events in a web browser, open the link returned by the following command: 

    $ kn service describe event-display -o url
    Copy to Clipboard Toggle word wrap

    Figure 4.1. Example browser page

    Example visualization of ApiServerSource event
    View larger image
    Example visualization of ApiServerSource event

  • Alternatively, to see the logs in the terminal, view the event-display logs for the pods by entering the following command: 

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container
    Copy to Clipboard Toggle word wrap

    Example output

    ☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.apiserver.resource.update
  datacontenttype: application/json
  ...
Data,
  {
    "apiVersion": "v1",
    "involvedObject": {
      "apiVersion": "v1",
      "fieldPath": "spec.containers{event-origin}",
      "kind": "Pod",
      "name": "event-origin",
      "namespace": "default",
       .....
    },
    "kind": "Event",
    "message": "Started container",
    "metadata": {
      "name": "event-origin.159d7608e3a3572c",
      "namespace": "default",
      ....
    },
    "reason": "Started",
    ...
  }
    Copy to Clipboard Toggle word wrap

Deleting the API server source

  1. Delete the trigger: 

    $ kn trigger delete <trigger_name>
    Copy to Clipboard Toggle word wrap

  2. Delete the event source: 

    $ kn source apiserver delete <source_name>
    Copy to Clipboard Toggle word wrap

  3. Delete the service account, cluster role, and cluster binding: 

    $ oc delete -f authentication.yaml
    Copy to Clipboard Toggle word wrap

You can use the kn source ping create command to create a ping source by using the Knative (kn) CLI. Using the Knative CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving and Knative Eventing are installed on the 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.
  • Optional: If you want to use the verification steps for this procedure, install the OpenShift CLI (oc).

Procedure

  1. To verify that the ping source is working, create a simple Knative service that dumps incoming messages to the service logs: 

    $ kn service create event-display \
    --image quay.io/openshift-knative/showcase
    Copy to Clipboard Toggle word wrap

  2. For each set of ping events that you want to request, create a ping source in the same namespace as the event consumer: 

    $ kn source ping create test-ping-source \
    --schedule "*/2 * * * *" \
    --data '{"message": "Hello world!"}' \
    --sink ksvc:event-display
    Copy to Clipboard Toggle word wrap

  3. Check that the controller is mapped correctly by entering the following command and inspecting the output: 

    $ kn source ping describe test-ping-source
    Copy to Clipboard Toggle word wrap

    Example output

    Name:         test-ping-source
Namespace:    default
Annotations:  sources.knative.dev/creator=developer, sources.knative.dev/lastModifier=developer
Age:          15s
Schedule:     */2 * * * *
Data:         {"message": "Hello world!"}

Sink:
  Name:       event-display
  Namespace:  default
  Resource:   Service (serving.knative.dev/v1)

Conditions:
  OK TYPE                 AGE REASON
  ++ Ready                 8s
  ++ Deployed              8s
  ++ SinkProvided         15s
  ++ ValidSchedule        15s
  ++ EventTypeProvided    15s
  ++ ResourcesCorrect     15s
    Copy to Clipboard Toggle word wrap

Verification

You can verify that the Kubernetes events were sent to the Knative event sink by looking at the logs of the sink pod.

By default, Knative services terminate their pods if no traffic is received within a 60 second period. The example shown in this guide creates a ping source that sends a message every 2 minutes, so each message should be observed in a newly created pod.

  1. Watch for new pods created: 

    $ watch oc get pods
    Copy to Clipboard Toggle word wrap

  2. Cancel watching the pods using Ctrl+C, then look at the logs of the created pod: 

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container
    Copy to Clipboard Toggle word wrap

    Example output

    ☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.sources.ping
  source: /apis/v1/namespaces/default/pingsources/test-ping-source
  id: 99e4f4f6-08ff-4bff-acf1-47f61ded68c9
  time: 2020-04-07T16:16:00.000601161Z
  datacontenttype: application/json
Data,
  {
    "message": "Hello world!"
  }
    Copy to Clipboard Toggle word wrap

Deleting the ping source

  • Delete the ping source: 

    $ kn delete pingsources.sources.knative.dev <ping_source_name>
    Copy to Clipboard Toggle word wrap

You can use the kn source kafka create command to create a Kafka source by using the Knative (kn) CLI. Using the Knative CLI to create event sources provides a more streamlined and intuitive user interface than modifying YAML files directly.

Prerequisites

  • The OpenShift Serverless Operator, Knative Eventing, Knative Serving, and the KnativeKafka custom resource (CR) are installed on your cluster.
  • 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 access to a Red Hat AMQ Streams (Kafka) cluster that produces the Kafka messages you want to import.
  • You have installed the Knative (kn) CLI.
  • Optional: You have installed the OpenShift CLI (oc) if you want to use the verification steps in this procedure.

Procedure

  1. To verify that the Kafka event source is working, create a Knative service that dumps incoming events into the service logs: 

    $ kn service create event-display \
    --image quay.io/openshift-knative/showcase
    Copy to Clipboard Toggle word wrap

  2. Create a KafkaSource CR: 

    $ kn source kafka create <kafka_source_name> \
    --servers <cluster_kafka_bootstrap>.kafka.svc:9092 \
    --topics <topic_name> --consumergroup my-consumer-group \
    --sink event-display
    Copy to Clipboard Toggle word wrap
    Note

    Replace the placeholder values in this command with values for your source name, bootstrap servers, and topics.

    The --servers, --topics, and --consumergroup options specify the connection parameters to the Kafka cluster. The --consumergroup option is optional.

  3. Optional: View details about the KafkaSource CR you created: 

    $ kn source kafka describe <kafka_source_name>
    Copy to Clipboard Toggle word wrap

    Example output

    Name:              example-kafka-source
Namespace:         kafka
Age:               1h
BootstrapServers:  example-cluster-kafka-bootstrap.kafka.svc:9092
Topics:            example-topic
ConsumerGroup:     example-consumer-group

Sink:
  Name:       event-display
  Namespace:  default
  Resource:   Service (serving.knative.dev/v1)

Conditions:
  OK TYPE            AGE REASON
  ++ Ready            1h
  ++ Deployed         1h
  ++ SinkProvided     1h
    Copy to Clipboard Toggle word wrap

Verification steps

  1. Trigger the Kafka instance to send a message to the topic: 

    $ oc -n kafka run kafka-producer \
    -ti --image=quay.io/strimzi/kafka:latest-kafka-2.7.0 --rm=true \
    --restart=Never -- bin/kafka-console-producer.sh \
    --broker-list <cluster_kafka_bootstrap>:9092 --topic my-topic
    Copy to Clipboard Toggle word wrap

    Enter the message in the prompt. This command assumes that:

    • The Kafka cluster is installed in the kafka namespace.
    • The KafkaSource object has been configured to use the my-topic topic.

  2. Verify that the message arrived by viewing the logs: 

    $ oc logs $(oc get pod -o name | grep event-display) -c user-container
    Copy to Clipboard Toggle word wrap

    Example output

    ☁️  cloudevents.Event
Validation: valid
Context Attributes,
  specversion: 1.0
  type: dev.knative.kafka.event
  source: /apis/v1/namespaces/default/kafkasources/example-kafka-source#example-topic
  subject: partition:46#0
  id: partition:46/offset:0
  time: 2021-03-10T11:21:49.4Z
Extensions,
  traceparent: 00-161ff3815727d8755848ec01c866d1cd-7ff3916c44334678-00
Data,
  Hello!
    Copy to Clipboard Toggle word wrap

Chapter 5. Knative Functions CLI commands
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5.1. kn functions commands
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You can specify the path, runtime, template, and image registry for a function as flags on the command line, or use the -c flag to start the interactive experience in the terminal.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the cluster.
  • You have installed the Knative (kn) CLI.

Procedure

  • Create a function project: 

    $ kn func create -r <repository> -l <runtime> -t <template> <path>
    Copy to Clipboard Toggle word wrap
    • Accepted runtime values include quarkus, node, typescript, go, python, springboot, and rust.

    • Accepted template values include http and cloudevents.

      Example command

      $ kn func create -l typescript -t cloudevents examplefunc
      Copy to Clipboard Toggle word wrap

      Example output

      Created typescript function in /home/user/demo/examplefunc
      Copy to Clipboard Toggle word wrap

    • Alternatively, you can specify a repository that contains a custom template.

      Example command

      $ kn func create -r https://github.com/boson-project/templates/ -l node -t hello-world examplefunc
      Copy to Clipboard Toggle word wrap

      Example output

      Created node function in /home/user/demo/examplefunc
      Copy to Clipboard Toggle word wrap

5.1.2. Running a function locally
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You can use the kn func run command to run a function locally in the current directory or in the directory specified by the --path flag. If the function that you are running has never previously been built, or if the project files have been modified since the last time it was built, the kn func run command builds the function before running it by default.

Example command to run a function in the current directory

$ kn func run
Copy to Clipboard Toggle word wrap

Example command to run a function in a directory specified as a path

$ kn func run --path=<directory_path>
Copy to Clipboard Toggle word wrap

You can also force a rebuild of an existing image before running the function, even if there have been no changes to the project files, by using the --build flag:

Example run command using the build flag

$ kn func run --build
Copy to Clipboard Toggle word wrap

If you set the build flag as false, this disables building of the image, and runs the function using the previously built image:

Example run command using the build flag

$ kn func run --build=false
Copy to Clipboard Toggle word wrap

You can use the help command to learn more about kn func run command options:

Build help command

$ kn func help run
Copy to Clipboard Toggle word wrap

5.1.3. Building a function
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Before you can run a function, you must build the function project. If you are using the kn func run command, the function is built automatically. However, you can use the kn func build command to build a function without running it, which can be useful for advanced users or debugging scenarios.

The kn func build command creates an OCI container image that can be run locally on your computer or on an OpenShift Container Platform cluster. This command uses the function project name and the image registry name to construct a fully qualified image name for your function.

5.1.3.1. Image container types
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By default, kn func build creates a container image by using Red Hat Source-to-Image (S2I) technology.

Example build command using Red Hat Source-to-Image (S2I)

$ kn func build
Copy to Clipboard Toggle word wrap

5.1.3.2. Image registry types
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The OpenShift Container Registry is used by default as the image registry for storing function images.

Example build command using OpenShift Container Registry

$ kn func build
Copy to Clipboard Toggle word wrap

Example output

Building function image
Function image has been built, image: registry.redhat.io/example/example-function:latest
Copy to Clipboard Toggle word wrap

You can override using OpenShift Container Registry as the default image registry by using the --registry flag:

Example build command overriding OpenShift Container Registry to use quay.io

$ kn func build --registry quay.io/username
Copy to Clipboard Toggle word wrap

Example output

Building function image
Function image has been built, image: quay.io/username/example-function:latest
Copy to Clipboard Toggle word wrap

5.1.3.3. Push flag
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You can add the --push flag to a kn func build command to automatically push the function image after it is successfully built:

Example build command using OpenShift Container Registry

$ kn func build --push
Copy to Clipboard Toggle word wrap

5.1.3.4. Help command
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You can use the help command to learn more about kn func build command options:

Build help command

$ kn func help build
Copy to Clipboard Toggle word wrap

5.1.4. Deploying a function
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You can deploy a function to your cluster as a Knative service by using the kn func deploy command. If the targeted function is already deployed, it is updated with a new container image that is pushed to a container image registry, and the Knative service is updated.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the 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.
  • You must have already created and initialized the function that you want to deploy.

Procedure

  • Deploy a function: 

    $ kn func deploy [-n <namespace> -p <path> -i <image>]
    Copy to Clipboard Toggle word wrap

    Example output

    Function deployed at: http://func.example.com
    Copy to Clipboard Toggle word wrap

    • If no namespace is specified, the function is deployed in the current namespace.
    • The function is deployed from the current directory, unless a path is specified.
    • The Knative service name is derived from the project name, and cannot be changed using this command.
Note

You can create a serverless function with a Git repository URL by using Import from Git or Create Serverless Function in the +Add view.

5.1.5. Listing existing functions
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You can list existing functions by using kn func list. If you want to list functions that have been deployed as Knative services, you can also use kn service list.

Procedure

  • List existing functions: 

    $ kn func list [-n <namespace> -p <path>]
    Copy to Clipboard Toggle word wrap

    Example output

    NAME           NAMESPACE  RUNTIME  URL                                                                                      READY
example-function  default    node     http://example-function.default.apps.ci-ln-g9f36hb-d5d6b.origin-ci-int-aws.dev.rhcloud.com  True
    Copy to Clipboard Toggle word wrap

  • List functions deployed as Knative services: 

    $ kn service list -n <namespace>
    Copy to Clipboard Toggle word wrap

    Example output

    NAME            URL                                                                                       LATEST                AGE   CONDITIONS   READY   REASON
example-function   http://example-function.default.apps.ci-ln-g9f36hb-d5d6b.origin-ci-int-aws.dev.rhcloud.com   example-function-gzl4c   16m   3 OK / 3     True
    Copy to Clipboard Toggle word wrap

5.1.6. Describing a function
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The kn func info command prints information about a deployed function, such as the function name, image, namespace, Knative service information, route information, and event subscriptions.

Procedure

  • Describe a function: 

    $ kn func info [-f <format> -n <namespace> -p <path>]
    Copy to Clipboard Toggle word wrap

    Example command

    $ kn func info -p function/example-function
    Copy to Clipboard Toggle word wrap

    Example output

    Function name:
  example-function
Function is built in image:
  docker.io/user/example-function:latest
Function is deployed as Knative Service:
  example-function
Function is deployed in namespace:
  default
Routes:
  http://example-function.default.apps.ci-ln-g9f36hb-d5d6b.origin-ci-int-aws.dev.rhcloud.com
    Copy to Clipboard Toggle word wrap

You can use the kn func invoke CLI command to send a test request to invoke a function either locally or on your OpenShift Container Platform cluster. You can use this command to test that a function is working and able to receive events correctly. Invoking a function locally is useful for a quick test during function development. Invoking a function on the cluster is useful for testing that is closer to the production environment.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the 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.
  • You must have already deployed the function that you want to invoke.

Procedure

  • Invoke a function: 

    $ kn func invoke
    Copy to Clipboard Toggle word wrap
    • The kn func invoke command only works when there is either a local container image currently running, or when there is a function deployed in the cluster.
    • The kn func invoke command executes on the local directory by default, and assumes that this directory is a function project.
5.1.7.1. kn func invoke optional parameters
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You can specify optional parameters for the request by using the following kn func invoke CLI command flags.

Expand
FlagsDescription

-t, --target

Specifies the target instance of the invoked function, for example, local or remote or https://staging.example.com/. The default target is local.

-f, --format

Specifies the format of the message, for example, cloudevent or http.

--id

Specifies a unique string identifier for the request.

-n, --namespace

Specifies the namespace on the cluster.

--source

Specifies sender name for the request. This corresponds to the CloudEvent source attribute.

--type

Specifies the type of request, for example, boson.fn. This corresponds to the CloudEvent type attribute.

--data

Specifies content for the request. For CloudEvent requests, this is the CloudEvent data attribute.

--file

Specifies path to a local file containing data to be sent.

--content-type

Specifies the MIME content type for the request.

-p, --path

Specifies path to the project directory.

-c, --confirm

Enables prompting to interactively confirm all options.

-v, --verbose

Enables printing verbose output.

-h, --help

Prints information on usage of kn func invoke.

5.1.7.1.1. Main parameters
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The following parameters define the main properties of the kn func invoke command:

Event target (-t, --target)
The target instance of the invoked function. Accepts the local value for a locally deployed function, the remote value for a remotely deployed function, or a URL for a function deployed to an arbitrary endpoint. If a target is not specified, it defaults to local.
Event message format (-f, --format)
The message format for the event, such as http or cloudevent. This defaults to the format of the template that was used when creating the function.
Event type (--type)
The type of event that is sent. You can find information about the type parameter that is set in the documentation for each event producer. For example, the API server source might set the type parameter of produced events as dev.knative.apiserver.resource.update.
Event source (--source)
The unique event source that produced the event. This might be a URI for the event source, for example https://10.96.0.1/, or the name of the event source.
Event ID (--id)
A random, unique ID that is created by the event producer.
Event data (--data)

Allows you to specify a data value for the event sent by the kn func invoke command. For example, you can specify a --data value such as "Hello World" so that the event contains this data string. By default, no data is included in the events created by kn func invoke.

Note

Functions that have been deployed to a cluster can respond to events from an existing event source that provides values for properties such as source and type. These events often have a data value in JSON format, which captures the domain specific context of the event. By using the CLI flags noted in this document, developers can simulate those events for local testing.

You can also send event data using the --file flag to provide a local file containing data for the event. In this case, specify the content type using --content-type.

Data content type (--content-type)
If you are using the --data flag to add data for events, you can use the --content-type flag to specify what type of data is carried by the event. In the previous example, the data is plain text, so you might specify kn func invoke --data "Hello world!" --content-type "text/plain".
5.1.7.1.2. Example commands
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This is the general invocation of the kn func invoke command: 

$ kn func invoke --type <event_type> --source <event_source> --data <event_data> --content-type <content_type> --id <event_ID> --format <format> --namespace <namespace>
Copy to Clipboard Toggle word wrap

For example, to send a "Hello world!" event, you can run: 

$ kn func invoke --type ping --source example-ping --data "Hello world!" --content-type "text/plain" --id example-ID --format http --namespace my-ns
Copy to Clipboard Toggle word wrap
5.1.7.1.2.1. Specifying the file with data
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To specify the file on disk that contains the event data, use the --file and --content-type flags: 

$ kn func invoke --file <path> --content-type <content-type>
Copy to Clipboard Toggle word wrap

For example, to send JSON data stored in the test.json file, use this command: 

$ kn func invoke --file ./test.json --content-type application/json
Copy to Clipboard Toggle word wrap
5.1.7.1.2.2. Specifying the function project
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You can specify a path to the function project by using the --path flag: 

$ kn func invoke --path <path_to_function>
Copy to Clipboard Toggle word wrap

For example, to use the function project located in the ./example/example-function directory, use this command: 

$ kn func invoke --path ./example/example-function
Copy to Clipboard Toggle word wrap

By default, kn func invoke targets the local deployment of the function: 

$ kn func invoke
Copy to Clipboard Toggle word wrap

To use a different deployment, use the --target flag: 

$ kn func invoke --target <target>
Copy to Clipboard Toggle word wrap

For example, to use the function deployed on the cluster, use the --target remote flag: 

$ kn func invoke --target remote
Copy to Clipboard Toggle word wrap

To use the function deployed at an arbitrary URL, use the --target <URL> flag: 

$ kn func invoke --target "https://my-event-broker.example.com"
Copy to Clipboard Toggle word wrap

You can explicitly target the local deployment. In this case, if the function is not running locally, the command fails: 

$ kn func invoke --target local
Copy to Clipboard Toggle word wrap

5.1.8. Deleting a function
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You can delete a function by using the kn func delete command. This is useful when a function is no longer required, and can help to save resources on your cluster.

Procedure

  • Delete a function: 

    $ kn func delete [<function_name> -n <namespace> -p <path>]
    Copy to Clipboard Toggle word wrap
    • If the name or path of the function to delete is not specified, the current directory is searched for a func.yaml file that is used to determine the function to delete.
    • If the namespace is not specified, it defaults to the namespace value in the func.yaml file.

Legal Notice
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Copyright © 2025 Red Hat, Inc.
The text of and illustrations in this document are licensed by Red Hat under a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA"). An explanation of CC-BY-SA is available at http://creativecommons.org/licenses/by-sa/3.0/. In accordance with CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the original version.
Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent permitted by applicable law.
Red Hat, Red Hat Enterprise Linux, the Shadowman logo, the Red Hat logo, JBoss, OpenShift, Fedora, the Infinity logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries.
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