×

Creating functions

Before you can build and deploy a function, you must create it by using the Knative (kn) CLI. You can specify the path, runtime, template, and image registry as flags on the command line, or use the -c flag to start the interactive experience in the terminal.

OpenShift Serverless Functions 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 https://access.redhat.com/support/offerings/techpreview/.

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>
    • 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
      Example output
      Created typescript function in /home/user/demo/examplefunc
    • 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
      Example output
      Created node function in /home/user/demo/examplefunc

Running a function locally

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
Example command to run a function in a directory specified as a path
$ kn func run --path=<directory_path>

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

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

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

Build help command
$ kn func help run

Building functions

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 Red Hat OpenShift Service on AWS cluster. This command uses the function project name and the image registry name to construct a fully qualified image name for your function.

Image container types

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

You can use CNCF Cloud Native Buildpacks technology instead, by adding the --builder flag to the command and specifying the pack strategy:

Example build command using CNCF Cloud Native Buildpacks
$ kn func build --builder pack

Image registry types

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
Example output
Building function image
Function image has been built, image: registry.redhat.io/example/example-function:latest

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
Example output
Building function image
Function image has been built, image: quay.io/username/example-function:latest

Push flag

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

Help command

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

Build help command
$ kn func help build

Deploying functions

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 Red Hat OpenShift Service on AWS.

  • 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>]
    Example output
    Function deployed at: http://func.example.com
    • 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.

Listing existing functions

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>]
    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
  • List functions deployed as Knative services:

    $ kn service list -n <namespace>
    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

Describing a function

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>]
    Example command
    $ kn func info -p function/example-function
    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

Invoking a deployed function with a test event

You can use the kn func invoke CLI command to send a test request to invoke a function either locally or on your Red Hat OpenShift Service on AWS 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 Red Hat OpenShift Service on AWS.

  • You must have already deployed the function that you want to invoke.

Procedure
  • Invoke a function:

    $ kn func invoke
    • 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.

kn func invoke optional parameters

You can specify optional parameters for the request by using the following kn func invoke CLI command flags.

Flags Description

-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.

Main parameters

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.

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".

Example commands

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>

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
Specifying the file with data

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>

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
Specifying the function project

You can specify a path to the function project by using the --path flag:

$ kn func invoke --path <path_to_function>

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

$ kn func invoke --path ./example/example-function
Specifying where the target function is deployed

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

$ kn func invoke

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

$ kn func invoke --target <target>

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

$ kn func invoke --target remote

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

$ kn func invoke --target "https://my-event-broker.example.com"

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

Deleting a function

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>]
    • 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.