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Chapter 11. Functions

11.1. Setting up OpenShift Serverless Functions

Important

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/.

To improve the process of deployment of your application code, you can use OpenShift Serverless to deploy stateless, event-driven functions as a Knative service on OpenShift Dedicated. If you want to develop functions, you must complete the set up steps.

11.1.1. Prerequisites

To enable the use of OpenShift Serverless Functions on your cluster, you must complete the following steps:

  • The OpenShift Serverless Operator and Knative Serving are installed on your cluster.

    Note

    Functions are deployed as a Knative service. If you want to use event-driven architecture with your functions, you must also install Knative Eventing.

  • The oc CLI is installed on your cluster.
  • The Knative (kn) CLI is installed on your cluster. Installing the Knative CLI enables the use of kn func commands which you can use to create and manage functions.
  • You have installed Docker Container Engine or podman version 3.3 or higher, and have access to an available image registry.
  • If you are using Quay.io as the image registry, you must ensure that either the repository is not private, or that you have allowed pods on your cluster to reference images from other secured registries.
  • If you are using the OpenShift Container Registry, a cluster or dedicated administrator must expose the registry.

11.1.2. Setting up podman

To use advanced container management features, you might want to use podman with OpenShift Serverless Functions. To do so, you need to start the podman service and configure the Knative (kn) CLI to connect to it.

Procedure

  1. Start the podman service that serves the Docker API on a UNIX socket at ${XDG_RUNTIME_DIR}/podman/podman.sock:

    $ systemctl start --user podman.socket
    Note

    On most systems, this socket is located at /run/user/$(id -u)/podman/podman.sock.

  2. Establish the environment variable that is used to build a function:

    $ export DOCKER_HOST="unix://${XDG_RUNTIME_DIR}/podman/podman.sock"
  3. Run the build command inside your function project directory with the -v flag to see verbose output. You should see a connection to your local UNIX socket:

    $ kn func build -v

11.1.3. Next steps

11.2. Getting started with functions

Function lifecycle management includes creating, building, and deploying a function. Optionally, you can also test a deployed function by invoking it. You can do all of these operations on OpenShift Serverless using the kn func tool.

Important

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/.

11.2.1. Prerequisites

Before you can complete the following procedures, you must ensure that you have completed all of the prerequisite tasks in Setting up OpenShift Serverless Functions.

11.2.2. 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.

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 node, go, python, quarkus, and typescript.
    • Accepted template values include http and events.

      Example command

      $ kn func create -l typescript -t events examplefunc

      Example output

      Project path:  /home/user/demo/examplefunc
      Function name: examplefunc
      Runtime:       typescript
      Template:      events
      Writing events to /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

      Project path:  /home/user/demo/examplefunc
      Function name: examplefunc
      Runtime:       node
      Template:      hello-world
      Writing events to /home/user/demo/examplefunc

11.2.3. 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

11.2.4. 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 OpenShift Dedicated cluster. This command uses the function project name and the image registry name to construct a fully qualified image name for your function.

11.2.4.1. 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

11.2.4.2. 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

11.2.4.3. 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

11.2.4.4. Help command

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

Build help command

$ kn func help build

11.2.5. Building and deploying functions on the cluster

You can use the Knative (kn) CLI to initiate a function project build and then deploy the function directly on the cluster. To build a function project in this way, the source code for your function project must exist in a Git repository branch that is accessible to your cluster.

Important

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

  • Red Hat OpenShift Pipelines must be installed on your cluster.
  • You have installed the OpenShift CLI (oc).
  • You have installed the Knative (kn) CLI.

Procedure

  1. In each namespace where you want to run Pipelines and deploy a function, you must create the following resources:

    1. Create the functions buildpacks Tekton task to be able to build the function image:

      $ oc apply -f https://raw.githubusercontent.com/openshift-knative/kn-plugin-func/serverless-1.22.0/pipelines/resources/tekton/task/func-buildpacks/0.1/func-buildpacks.yaml
    2. Create the kn func deploy Tekton task to be able to deploy the function in the pipeline:

      $ oc apply -f https://raw.githubusercontent.com/openshift-knative/kn-plugin-func/serverless-1.22.0/pipelines/resources/tekton/task/func-deploy/0.1/func-deploy.yaml
  2. Create a function:

    $ kn func create <function_name> -l <runtime>
  3. After you have created a new function project, you must add the project to a Git repository and ensure that the repository is available to the cluster. Information about this Git repository is used to update the func.yaml file in the next step.
  4. Update the configuration in the func.yaml file for your function project to enable on-cluster builds for the Git repository:

    ...
    build: git 1
    git:
      url: <git_repository_url> 2
      revision: main 3
      contextDir: <directory_path> 4
    ...
    1
    Required. Specify git build type.
    2
    Required. Specify the Git repository that contains your function’s source code.
    3
    Optional. Specify the Git repository revision to be used. This can be a branch, tag or commit.
    4
    Optional. Specify the function’s directory path if the function is not located in the Git repository root folder.
  5. Implement the business logic of your function. Then, use Git to commit and push the changes.
  6. Deploy your function:

    $ kn func deploy

    If you are not logged into the container registry referenced in your function configuration, you are prompted to provide credentials for the remote container registry that hosts the function image:

    Example output and prompts

    🕕 Creating Pipeline resources
    Please provide credentials for image registry used by Pipeline.
    ? Server: https://index.docker.io/v1/
    ? Username: my-repo
    ? Password: ********
       Function deployed at URL: http://test-function.default.svc.cluster.local

  7. To update your function, commit and push new changes by using Git, then run the kn func deploy command again.

11.2.6. 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 OpenShift Dedicated.
  • 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.

11.2.7. 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 OpenShift Dedicated cluster. This command can be used to test that a function is working and able to receive events correctly.

Example command

$ kn func invoke

The kn func invoke command executes on the local directory by default, and assumes that this directory is a function project.

11.2.8. Next steps

11.3. Developing Node.js functions

Important

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/.

After you have created a Node.js function project, you can modify the template files provided to add business logic to your function. This includes configuring function invocation and the returned headers and status codes.

11.3.1. Prerequisites

11.3.2. Node.js function template structure

When you create a Node.js function using the Knative (kn) CLI, the project directory looks like a typical Node.js project. The only exception is the additional func.yaml file, which is used to configure the function.

Both http and event trigger functions have the same template structure:

Template structure

.
├── func.yaml 1
├── index.js 2
├── package.json 3
├── README.md
└── test 4
    ├── integration.js
    └── unit.js

1
The func.yaml configuration file is used to determine the image name and registry.
2
Your project must contain an index.js file which exports a single function.
3
You are not restricted to the dependencies provided in the template package.json file. You can add additional dependencies as you would in any other Node.js project.

Example of adding npm dependencies

npm install --save opossum

When the project is built for deployment, these dependencies are included in the created runtime container image.

4
Integration and unit test scripts are provided as part of the function template.

11.3.3. About invoking Node.js functions

When using the Knative (kn) CLI to create a function project, you can generate a project that responds to CloudEvents, or one that responds to simple HTTP requests. CloudEvents in Knative are transported over HTTP as a POST request, so both function types listen for and respond to incoming HTTP events.

Node.js functions can be invoked with a simple HTTP request. When an incoming request is received, functions are invoked with a context object as the first parameter.

11.3.3.1. Node.js context objects

Functions are invoked by providing a context object as the first parameter. This object provides access to the incoming HTTP request information.

Example context object

function handle(context, data)

This information includes the HTTP request method, any query strings or headers sent with the request, the HTTP version, and the request body. Incoming requests that contain a CloudEvent attach the incoming instance of the CloudEvent to the context object so that it can be accessed by using context.cloudevent.

11.3.3.1.1. Context object methods

The context object has a single method, cloudEventResponse(), that accepts a data value and returns a CloudEvent.

In a Knative system, if a function deployed as a service is invoked by an event broker sending a CloudEvent, the broker examines the response. If the response is a CloudEvent, this event is handled by the broker.

Example context object method

// Expects to receive a CloudEvent with customer data
function handle(context, customer) {
  // process the customer
  const processed = handle(customer);
  return context.cloudEventResponse(customer)
    .source('/handle')
    .type('fn.process.customer')
    .response();
}

11.3.3.1.2. CloudEvent data

If the incoming request is a CloudEvent, any data associated with the CloudEvent is extracted from the event and provided as a second parameter. For example, if a CloudEvent is received that contains a JSON string in its data property that is similar to the following:

{
  "customerId": "0123456",
  "productId": "6543210"
}

When invoked, the second parameter to the function, after the context object, will be a JavaScript object that has customerId and productId properties.

Example signature

function handle(context, data)

The data parameter in this example is a JavaScript object that contains the customerId and productId properties.

11.3.4. Node.js function return values

Functions can return any valid JavaScript type or can have no return value. When a function has no return value specified, and no failure is indicated, the caller receives a 204 No Content response.

Functions can also return a CloudEvent or a Message object in order to push events into the Knative Eventing system. In this case, the developer is not required to understand or implement the CloudEvent messaging specification. Headers and other relevant information from the returned values are extracted and sent with the response.

Example

function handle(context, customer) {
  // process customer and return a new CloudEvent
  return new CloudEvent({
    source: 'customer.processor',
    type: 'customer.processed'
  })
}

11.3.4.1. Returning headers

You can set a response header by adding a headers property to the return object. These headers are extracted and sent with the response to the caller.

Example response header

function handle(context, customer) {
  // process customer and return custom headers
  // the response will be '204 No content'
  return { headers: { customerid: customer.id } };
}

11.3.4.2. Returning status codes

You can set a status code that is returned to the caller by adding a statusCode property to the return object:

Example status code

function handle(context, customer) {
  // process customer
  if (customer.restricted) {
    return { statusCode: 451 }
  }
}

Status codes can also be set for errors that are created and thrown by the function:

Example error status code

function handle(context, customer) {
  // process customer
  if (customer.restricted) {
    const err = new Error(‘Unavailable for legal reasons’);
    err.statusCode = 451;
    throw err;
  }
}

11.3.5. Testing Node.js functions

Node.js functions can be tested locally on your computer. In the default project that is created when you create a function by using kn func create, there is a test folder that contains some simple unit and integration tests.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the cluster.
  • You have installed the Knative (kn) CLI.
  • You have created a function by using kn func create.

Procedure

  1. Navigate to the test folder for your function.
  2. Run the tests:

    $ npm test

11.3.6. Next steps

11.4. Developing TypeScript functions

Important

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/.

After you have created a TypeScript function project, you can modify the template files provided to add business logic to your function. This includes configuring function invocation and the returned headers and status codes.

11.4.1. Prerequisites

11.4.2. TypeScript function template structure

When you create a TypeScript function using the Knative (kn) CLI, the project directory looks like a typical TypeScript project. The only exception is the additional func.yaml file, which is used for configuring the function.

Both http and event trigger functions have the same template structure:

Template structure

.
├── func.yaml 1
├── package.json 2
├── package-lock.json
├── README.md
├── src
│   └── index.ts 3
├── test 4
│   ├── integration.ts
│   └── unit.ts
└── tsconfig.json

1
The func.yaml configuration file is used to determine the image name and registry.
2
You are not restricted to the dependencies provided in the template package.json file. You can add additional dependencies as you would in any other TypeScript project.

Example of adding npm dependencies

npm install --save opossum

When the project is built for deployment, these dependencies are included in the created runtime container image.

3
Your project must contain an src/index.js file which exports a function named handle.
4
Integration and unit test scripts are provided as part of the function template.

11.4.3. About invoking TypeScript functions

When using the Knative (kn) CLI to create a function project, you can generate a project that responds to CloudEvents or one that responds to simple HTTP requests. CloudEvents in Knative are transported over HTTP as a POST request, so both function types listen for and respond to incoming HTTP events.

TypeScript functions can be invoked with a simple HTTP request. When an incoming request is received, functions are invoked with a context object as the first parameter.

11.4.3.1. TypeScript context objects

To invoke a function, you provide a context object as the first parameter. Accessing properties of the context object can provide information about the incoming HTTP request.

Example context object

function handle(context:Context): string

This information includes the HTTP request method, any query strings or headers sent with the request, the HTTP version, and the request body. Incoming requests that contain a CloudEvent attach the incoming instance of the CloudEvent to the context object so that it can be accessed by using context.cloudevent.

11.4.3.1.1. Context object methods

The context object has a single method, cloudEventResponse(), that accepts a data value and returns a CloudEvent.

In a Knative system, if a function deployed as a service is invoked by an event broker sending a CloudEvent, the broker examines the response. If the response is a CloudEvent, this event is handled by the broker.

Example context object method

// Expects to receive a CloudEvent with customer data
export function handle(context: Context, cloudevent?: CloudEvent): CloudEvent {
  // process the customer
  const customer = cloudevent.data;
  const processed = processCustomer(customer);
  return context.cloudEventResponse(customer)
    .source('/customer/process')
    .type('customer.processed')
    .response();
}

11.4.3.1.2. Context types

The TypeScript type definition files export the following types for use in your functions.

Exported type definitions

// Invokable is the expeted Function signature for user functions
export interface Invokable {
    (context: Context, cloudevent?: CloudEvent): any
}

// Logger can be used for structural logging to the console
export interface Logger {
  debug: (msg: any) => void,
  info:  (msg: any) => void,
  warn:  (msg: any) => void,
  error: (msg: any) => void,
  fatal: (msg: any) => void,
  trace: (msg: any) => void,
}

// Context represents the function invocation context, and provides
// access to the event itself as well as raw HTTP objects.
export interface Context {
    log: Logger;
    req: IncomingMessage;
    query?: Record<string, any>;
    body?: Record<string, any>|string;
    method: string;
    headers: IncomingHttpHeaders;
    httpVersion: string;
    httpVersionMajor: number;
    httpVersionMinor: number;
    cloudevent: CloudEvent;
    cloudEventResponse(data: string|object): CloudEventResponse;
}

// CloudEventResponse is a convenience class used to create
// CloudEvents on function returns
export interface CloudEventResponse {
    id(id: string): CloudEventResponse;
    source(source: string): CloudEventResponse;
    type(type: string): CloudEventResponse;
    version(version: string): CloudEventResponse;
    response(): CloudEvent;
}

11.4.3.1.3. CloudEvent data

If the incoming request is a CloudEvent, any data associated with the CloudEvent is extracted from the event and provided as a second parameter. For example, if a CloudEvent is received that contains a JSON string in its data property that is similar to the following:

{
  "customerId": "0123456",
  "productId": "6543210"
}

When invoked, the second parameter to the function, after the context object, will be a JavaScript object that has customerId and productId properties.

Example signature

function handle(context: Context, cloudevent?: CloudEvent): CloudEvent

The cloudevent parameter in this example is a JavaScript object that contains the customerId and productId properties.

11.4.4. TypeScript function return values

Functions can return any valid JavaScript type or can have no return value. When a function has no return value specified, and no failure is indicated, the caller receives a 204 No Content response.

Functions can also return a CloudEvent or a Message object in order to push events into the Knative Eventing system. In this case, the developer is not required to understand or implement the CloudEvent messaging specification. Headers and other relevant information from the returned values are extracted and sent with the response.

Example

export const handle: Invokable = function (
  context: Context,
  cloudevent?: CloudEvent
): Message {
  // process customer and return a new CloudEvent
  const customer = cloudevent.data;
  return HTTP.binary(
    new CloudEvent({
      source: 'customer.processor',
      type: 'customer.processed'
    })
  );
};

11.4.4.1. Returning headers

You can set a response header by adding a headers property to the return object. These headers are extracted and sent with the response to the caller.

Example response header

export function handle(context: Context, cloudevent?: CloudEvent): Record<string, any> {
  // process customer and return custom headers
  const customer = cloudevent.data as Record<string, any>;
  return { headers: { 'customer-id': customer.id } };
}

11.4.4.2. Returning status codes

You can set a status code that is returned to the caller by adding a statusCode property to the return object:

Example status code

export function handle(context: Context, cloudevent?: CloudEvent): Record<string, any> {
  // process customer
  const customer = cloudevent.data as Record<string, any>;
  if (customer.restricted) {
    return {
      statusCode: 451
    }
  }
  // business logic, then
  return {
    statusCode: 240
  }
}

Status codes can also be set for errors that are created and thrown by the function:

Example error status code

export function handle(context: Context, cloudevent?: CloudEvent): Record<string, string> {
  // process customer
  const customer = cloudevent.data as Record<string, any>;
  if (customer.restricted) {
    const err = new Error(‘Unavailable for legal reasons’);
    err.statusCode = 451;
    throw err;
  }
}

11.4.5. Testing TypeScript functions

TypeScript functions can be tested locally on your computer. In the default project that is created when you create a function using kn func create, there is a test folder that contains some simple unit and integration tests.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the cluster.
  • You have installed the Knative (kn) CLI.
  • You have created a function by using kn func create.

Procedure

  1. If you have not previously run tests, install the dependencies first:

    $ npm install
  2. Navigate to the test folder for your function.
  3. Run the tests:

    $ npm test

11.4.6. Next steps

11.5. Developing Go functions

Important

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/.

After you have created a Go function project, you can modify the template files provided to add business logic to your function. This includes configuring function invocation and the returned headers and status codes.

11.5.1. Prerequisites

11.5.2. Go function template structure

When you create a Go function using the Knative (kn) CLI, the project directory looks like a typical Go project. The only exception is the additional func.yaml configuration file, which is used for specifying the image.

Go functions have few restrictions. The only requirements are that your project must be defined in a function module, and must export the function Handle().

Both http and event trigger functions have the same template structure:

Template structure

fn
├── README.md
├── func.yaml 1
├── go.mod 2
├── go.sum
├── handle.go
└── handle_test.go

1
The func.yaml configuration file is used to determine the image name and registry.
2
You can add any required dependencies to the go.mod file, which can include additional local Go files. When the project is built for deployment, these dependencies are included in the resulting runtime container image.

Example of adding dependencies

$ go get gopkg.in/yaml.v2@v2.4.0

11.5.3. About invoking Go functions

When using the Knative (kn) CLI to create a function project, you can generate a project that responds to CloudEvents, or one that responds to simple HTTP requests. Go functions are invoked by using different methods, depending on whether they are triggered by an HTTP request or a CloudEvent.

11.5.3.1. Functions triggered by an HTTP request

When an incoming HTTP request is received, functions are invoked with a standard Go Context as the first parameter, followed by the http.ResponseWriter and http.Request parameters. You can use standard Go techniques to access the request, and set a corresponding HTTP response for your function.

Example HTTP response

func Handle(ctx context.Context, res http.ResponseWriter, req *http.Request) {
  // Read body
  body, err := ioutil.ReadAll(req.Body)
  defer req.Body.Close()
  if err != nil {
	http.Error(res, err.Error(), 500)
	return
  }
  // Process body and function logic
  // ...
}

11.5.3.2. Functions triggered by a cloud event

When an incoming cloud event is received, the event is invoked by the CloudEvents Go SDK. The invocation uses the Event type as a parameter.

You can leverage the Go Context as an optional parameter in the function contract, as shown in the list of supported function signatures:

Supported function signatures

Handle()
Handle() error
Handle(context.Context)
Handle(context.Context) error
Handle(cloudevents.Event)
Handle(cloudevents.Event) error
Handle(context.Context, cloudevents.Event)
Handle(context.Context, cloudevents.Event) error
Handle(cloudevents.Event) *cloudevents.Event
Handle(cloudevents.Event) (*cloudevents.Event, error)
Handle(context.Context, cloudevents.Event) *cloudevents.Event
Handle(context.Context, cloudevents.Event) (*cloudevents.Event, error)

11.5.3.2.1. CloudEvent trigger example

A cloud event is received which contains a JSON string in the data property:

{
  "customerId": "0123456",
  "productId": "6543210"
}

To access this data, a structure must be defined which maps properties in the cloud event data, and retrieves the data from the incoming event. The following example uses the Purchase structure:

type Purchase struct {
  CustomerId string `json:"customerId"`
  ProductId  string `json:"productId"`
}
func Handle(ctx context.Context, event cloudevents.Event) (err error) {

  purchase := &Purchase{}
  if err = event.DataAs(purchase); err != nil {
	fmt.Fprintf(os.Stderr, "failed to parse incoming CloudEvent %s\n", err)
	return
  }
  // ...
}

Alternatively, a Go encoding/json package could be used to access the cloud event directly as JSON in the form of a bytes array:

func Handle(ctx context.Context, event cloudevents.Event) {
  bytes, err := json.Marshal(event)
  // ...
}

11.5.4. Go function return values

Functions triggered by HTTP requests can set the response directly. You can configure the function to do this by using the Go http.ResponseWriter.

Example HTTP response

func Handle(ctx context.Context, res http.ResponseWriter, req *http.Request) {
  // Set response
  res.Header().Add("Content-Type", "text/plain")
  res.Header().Add("Content-Length", "3")
  res.WriteHeader(200)
  _, err := fmt.Fprintf(res, "OK\n")
  if err != nil {
	fmt.Fprintf(os.Stderr, "error or response write: %v", err)
  }
}

Functions triggered by a cloud event might return nothing, error, or CloudEvent in order to push events into the Knative Eventing system. In this case, you must set a unique ID, proper Source, and a Type for the cloud event. The data can be populated from a defined structure, or from a map.

Example CloudEvent response

func Handle(ctx context.Context, event cloudevents.Event) (resp *cloudevents.Event, err error) {
  // ...
  response := cloudevents.NewEvent()
  response.SetID("example-uuid-32943bac6fea")
  response.SetSource("purchase/getter")
  response.SetType("purchase")
  // Set the data from Purchase type
  response.SetData(cloudevents.ApplicationJSON, Purchase{
	CustomerId: custId,
	ProductId:  prodId,
  })
  // OR set the data directly from map
  response.SetData(cloudevents.ApplicationJSON, map[string]string{"customerId": custId, "productId": prodId})
  // Validate the response
  resp = &response
  if err = resp.Validate(); err != nil {
	fmt.Printf("invalid event created. %v", err)
  }
  return
}

11.5.5. Testing Go functions

Go functions can be tested locally on your computer. In the default project that is created when you create a function using kn func create, there is a handle_test.go file, which contains some basic tests. These tests can be extended as needed.

Prerequisites

  • The OpenShift Serverless Operator and Knative Serving are installed on the cluster.
  • You have installed the Knative (kn) CLI.
  • You have created a function by using kn func create.

Procedure

  1. Navigate to the test folder for your function.
  2. Run the tests:

    $ go test

11.5.6. Next steps

11.6. Developing Python functions

Important

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/.

After you have created a Python function project, you can modify the template files provided to add business logic to your function. This includes configuring function invocation and the returned headers and status codes.

11.6.1. Prerequisites

11.6.2. Python function template structure

When you create a Python function by using the Knative (kn) CLI, the project directory looks similar to a typical Python project. Python functions have very few restrictions. The only requirements are that your project contains a func.py file that contains a main() function, and a func.yaml configuration file.

Developers are not restricted to the dependencies provided in the template requirements.txt file. Additional dependencies can be added as they would be in any other Python project. When the project is built for deployment, these dependencies will be included in the created runtime container image.

Both http and event trigger functions have the same template structure:

Template structure

fn
├── func.py 1
├── func.yaml 2
├── requirements.txt 3
└── test_func.py 4

1
Contains a main() function.
2
Used to determine the image name and registry.
3
Additional dependencies can be added to the requirements.txt file as they are in any other Python project.
4
Contains a simple unit test that can be used to test your function locally.

11.6.3. About invoking Python functions

Python functions can be invoked with a simple HTTP request. When an incoming request is received, functions are invoked with a context object as the first parameter.

The context object is a Python class with two attributes:

  • The request attribute is always present, and contains the Flask request object.
  • The second attribute, cloud_event, is populated if the incoming request is a CloudEvent object.

Developers can access any CloudEvent data from the context object.

Example context object

def main(context: Context):
    """
    The context parameter contains the Flask request object and any
    CloudEvent received with the request.
    """
    print(f"Method: {context.request.method}")
    print(f"Event data {context.cloud_event.data}")
    # ... business logic here

11.6.4. Python function return values

Functions can return any value supported by Flask. This is because the invocation framework proxies these values directly to the Flask server.

Example

def main(context: Context):
    body = { "message": "Howdy!" }
    headers = { "content-type": "application/json" }
    return body, 200, headers

Functions can set both headers and response codes as secondary and tertiary response values from function invocation.

11.6.4.1. Returning CloudEvents

Developers can use the @event decorator to tell the invoker that the function return value must be converted to a CloudEvent before sending the response.

Example

@event("event_source"="/my/function", "event_type"="my.type")
def main(context):
    # business logic here
    data = do_something()
    # more data processing
    return data

This example sends a CloudEvent as the response value, with a type of "my.type" and a source of "/my/function". The CloudEvent data property is set to the returned data variable. The event_source and event_type decorator attributes are both optional.

11.6.5. Testing Python functions

You can test Python functions locally on your computer. The default project contains a test_func.py file, which provides a simple unit test for functions.

Note

The default test framework for Python functions is unittest. You can use a different test framework if you prefer.

Prerequisites

  • To run Python functions tests locally, you must install the required dependencies:

    $ pip install -r requirements.txt

Procedure

  1. Navigate to the folder for your function that contains the test_func.py file.
  2. Run the tests:

    $ python3 test_func.py

11.6.6. Next steps

11.7. Developing Quarkus functions

Important

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/.

After you have created a Quarkus function project, you can modify the template files provided to add business logic to your function. This includes configuring function invocation and the returned headers and status codes.

11.7.1. Prerequisites

11.7.2. Quarkus function template structure

When you create a Quarkus function by using the Knative (kn) CLI, the project directory looks similar to a typical Maven project. Additionally, the project contains the func.yaml file, which is used for configuring the function.

Both http and event trigger functions have the same template structure:

Template structure

.
├── func.yaml 1
├── mvnw
├── mvnw.cmd
├── pom.xml 2
├── README.md
└── src
    ├── main
    │   ├── java
    │   │   └── functions
    │   │       ├── Function.java 3
    │   │       ├── Input.java
    │   │       └── Output.java
    │   └── resources
    │       └── application.properties
    └── test
        └── java
            └── functions 4
                ├── FunctionTest.java
                └── NativeFunctionIT.java

1
Used to determine the image name and registry.
2
The Project Object Model (POM) file contains project configuration, such as information about dependencies. You can add additional dependencies by modifying this file.

Example of additional dependencies

...
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.assertj</groupId>
      <artifactId>assertj-core</artifactId>
      <version>3.8.0</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
...

Dependencies are downloaded during the first compilation.

3
The function project must contain a Java method annotated with @Funq. You can place this method in the Function.java class.
4
Contains simple test cases that can be used to test your function locally.

11.7.3. About invoking Quarkus functions

You can create a Quarkus project that responds to cloud events, or one that responds to simple HTTP requests. Cloud events in Knative are transported over HTTP as a POST request, so either function type can listen and respond to incoming HTTP requests.

When an incoming request is received, Quarkus functions are invoked with an instance of a permitted type.

Table 11.1. Function invocation options

Invocation methodData type contained in the instanceExample of data

HTTP POST request

JSON object in the body of the request

{ "customerId": "0123456", "productId": "6543210" }

HTTP GET request

Data in the query string

?customerId=0123456&productId=6543210

CloudEvent

JSON object in the data property

{ "customerId": "0123456", "productId": "6543210" }

The following example shows a function that receives and processes the customerId and productId purchase data that is listed in the previous table:

Example Quarkus function

public class Functions {
    @Funq
    public void processPurchase(Purchase purchase) {
        // process the purchase
    }
}

The corresponding Purchase JavaBean class that contains the purchase data looks as follows:

Example class

public class Purchase {
    private long customerId;
    private long productId;
    // getters and setters
}

11.7.3.1. Invocation examples

The following example code defines three functions named withBeans, withCloudEvent, and withBinary;

Example

import io.quarkus.funqy.Funq;
import io.quarkus.funqy.knative.events.CloudEvent;

public class Input {
    private String message;

    // getters and setters
}

public class Output {
    private String message;

    // getters and setters
}

public class Functions {
    @Funq
    public Output withBeans(Input in) {
        // function body
    }

    @Funq
    public CloudEvent<Output> withCloudEvent(CloudEvent<Input> in) {
        // function body
    }

    @Funq
    public void withBinary(byte[] in) {
        // function body
    }
}

The withBeans function of the Functions class can be invoked by:

  • An HTTP POST request with a JSON body:

    $ curl "http://localhost:8080/withBeans" -X POST \
        -H "Content-Type: application/json" \
        -d '{"message": "Hello there."}'
  • An HTTP GET request with query parameters:

    $ curl "http://localhost:8080/withBeans?message=Hello%20there." -X GET
  • A CloudEvent object in binary encoding:

    $ curl "http://localhost:8080/" -X POST \
      -H "Content-Type: application/json" \
      -H "Ce-SpecVersion: 1.0" \
      -H "Ce-Type: withBeans" \
      -H "Ce-Source: cURL" \
      -H "Ce-Id: 42" \
      -d '{"message": "Hello there."}'
  • A CloudEvent object in structured encoding:

    $ curl http://localhost:8080/ \
        -H "Content-Type: application/cloudevents+json" \
        -d '{ "data": {"message":"Hello there."},
              "datacontenttype": "application/json",
              "id": "42",
              "source": "curl",
              "type": "withBeans",
              "specversion": "1.0"}'

The withCloudEvent function of the Functions class can be invoked by using a CloudEvent object, similarly to the withBeans function. However, unlike withBeans, withCloudEvent cannot be invoked with a plain HTTP request.

The withBinary function of the Functions class can be invoked by:

  • A CloudEvent object in binary encoding:

    $ curl "http://localhost:8080/" -X POST \
      -H "Content-Type: application/octet-stream" \
      -H "Ce-SpecVersion: 1.0"\
      -H "Ce-Type: withBinary" \
      -H "Ce-Source: cURL" \
      -H "Ce-Id: 42" \
      --data-binary '@img.jpg'
  • A CloudEvent object in structured encoding:

    $ curl http://localhost:8080/ \
      -H "Content-Type: application/cloudevents+json" \
      -d "{ \"data_base64\": \"$(base64 --wrap=0 img.jpg)\",
            \"datacontenttype\": \"application/octet-stream\",
            \"id\": \"42\",
            \"source\": \"curl\",
            \"type\": \"withBinary\",
            \"specversion\": \"1.0\"}"

11.7.4. CloudEvent attributes

If you need to read or write the attributes of a CloudEvent, such as type or subject, you can use the CloudEvent<T> generic interface and the CloudEventBuilder builder. The <T> type parameter must be one of the permitted types.

In the following example, CloudEventBuilder is used to return success or failure of processing the purchase:

public class Functions {

    private boolean _processPurchase(Purchase purchase) {
        // do stuff
    }

    public CloudEvent<Void> processPurchase(CloudEvent<Purchase> purchaseEvent) {
        System.out.println("subject is: " + purchaseEvent.subject());

        if (!_processPurchase(purchaseEvent.data())) {
            return CloudEventBuilder.create()
                    .type("purchase.error")
                    .build();
        }
        return CloudEventBuilder.create()
                .type("purchase.success")
                .build();
    }
}

11.7.5. Quarkus function return values

Functions can return an instance of any type from the list of permitted types. Alternatively, they can return the Uni<T> type, where the <T> type parameter can be of any type from the permitted types.

The Uni<T> type is useful if a function calls asynchronous APIs, because the returned object is serialized in the same format as the received object. For example:

  • If a function receives an HTTP request, then the returned object is sent in the body of an HTTP response.
  • If a function receives a CloudEvent object in binary encoding, then the returned object is sent in the data property of a binary-encoded CloudEvent object.

The following example shows a function that fetches a list of purchases:

Example command

public class Functions {
    @Funq
    public List<Purchase> getPurchasesByName(String name) {
      // logic to retrieve purchases
    }
}

  • Invoking this function through an HTTP request produces an HTTP response that contains a list of purchases in the body of the response.
  • Invoking this function through an incoming CloudEvent object produces a CloudEvent response with a list of purchases in the data property.

11.7.5.1. Permitted types

The input and output of a function can be any of the void, String, or byte[] types. Additionally, they can be primitive types and their wrappers, for example, int and Integer. They can also be the following complex objects: Javabeans, maps, lists, arrays, and the special CloudEvents<T> type.

Maps, lists, arrays, the <T> type parameter of the CloudEvents<T> type, and attributes of Javabeans can only be of types listed here.

Example

public class Functions {
    public List<Integer> getIds();
    public Purchase[] getPurchasesByName(String name);
    public String getNameById(int id);
    public Map<String,Integer> getNameIdMapping();
    public void processImage(byte[] img);
}

11.7.6. Testing Quarkus functions

Quarkus functions can be tested locally on your computer. In the default project that is created when you create a function using kn func create, there is the src/test/ directory, which contains basic Maven tests. These tests can be extended as needed.

Prerequisites

  • You have created a Quarkus function.
  • You have installed the Knative (kn) CLI.

Procedure

  1. Navigate to the project folder for your function.
  2. Run the Maven tests:

    $ ./mvnw test

11.7.7. Next steps

11.8. Using functions with Knative Eventing

Functions are deployed as Knative services on an OpenShift Dedicated cluster. You can connect functions to Knative Eventing components so that they can receive incoming events.

Important

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/.

11.8.1. Connect an event source to a function using the Developer perspective

Functions are deployed as Knative services on an OpenShift Dedicated cluster. When you create an event source by using the OpenShift Dedicated web console, you can specify a deployed function that events are sent to from that source.

Prerequisites

  • The OpenShift Serverless Operator, Knative Serving, and Knative Eventing are installed on your OpenShift Dedicated cluster.
  • You have logged in to the web console and are in the Developer perspective.
  • 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 Dedicated.
  • You have created and deployed a function.

Procedure

  1. Create an event source of any type, by navigating to +AddEvent Source and selecting the event source type that you want to create.
  2. In the Sink section of the Create Event Source form view, select your function in the Resource list.
  3. Click Create.

Verification

You can verify that the event source was created and is connected to the function by viewing the Topology page.

  1. In the Developer perspective, navigate to Topology.
  2. View the event source and click the connected function to see the function details in the right panel.

11.9. Function project configuration in func.yaml

The func.yaml file contains the configuration for your function project. Values specified in func.yaml are used when you execute a kn func command. For example, when you run the kn func build command, the value in the build field is used. In some cases, you can override these values with command line flags or environment variables.

11.9.1. Configurable fields in func.yaml

Many of the fields in func.yaml are generated automatically when you create, build, and deploy your function. However, there are also fields that you modify manually to change things, such as the function name or the image name.

11.9.1.1. buildEnvs

The buildEnvs field enables you to set environment variables to be available to the environment that builds your function. Unlike variables set using envs, a variable set using buildEnv is not available during function runtime.

You can set a buildEnv variable directly from a value. In the following example, the buildEnv variable named EXAMPLE1 is directly assigned the one value:

buildEnvs:
- name: EXAMPLE1
  value: one

You can also set a buildEnv variable from a local environment variable. In the following example, the buildEnv variable named EXAMPLE2 is assigned the value of the LOCAL_ENV_VAR local environment variable:

buildEnvs:
- name: EXAMPLE1
  value: '{{ env:LOCAL_ENV_VAR }}'

11.9.1.2. envs

The envs field enables you to set environment variables to be available to your function at runtime. You can set an environment variable in several different ways:

  1. Directly from a value.
  2. From a value assigned to a local environment variable. See the section "Referencing local environment variables from func.yaml fields" for more information.
  3. From a key-value pair stored in a secret or config map.
  4. You can also import all key-value pairs stored in a secret or config map, with keys used as names of the created environment variables.

This examples demonstrates the different ways to set an environment variable:

name: test
namespace: ""
runtime: go
...
envs:
- name: EXAMPLE1 1
  value: value
- name: EXAMPLE2 2
  value: '{{ env:LOCAL_ENV_VALUE }}'
- name: EXAMPLE3 3
  value: '{{ secret:mysecret:key }}'
- name: EXAMPLE4 4
  value: '{{ configMap:myconfigmap:key }}'
- value: '{{ secret:mysecret2 }}' 5
- value: '{{ configMap:myconfigmap2 }}' 6
1
An environment variable set directly from a value.
2
An environment variable set from a value assigned to a local environment variable.
3
An environment variable assigned from a key-value pair stored in a secret.
4
An environment variable assigned from a key-value pair stored in a config map.
5
A set of environment variables imported from key-value pairs of a secret.
6
A set of environment variables imported from key-value pairs of a config map.

11.9.1.3. builder

The builder field specifies the strategy used by the function to build the image. It accepts values of pack or s2i.

11.9.1.4. build

The build field indicates how the function should be built. The value local indicates that the function is built locally on your machine. The value git indicates that the function is built on a cluster by using the values specified in the git field.

11.9.1.5. volumes

The volumes field enables you to mount secrets and config maps as a volume accessible to the function at the specified path, as shown in the following example:

name: test
namespace: ""
runtime: go
...
volumes:
- secret: mysecret 1
  path: /workspace/secret
- configMap: myconfigmap 2
  path: /workspace/configmap
1
The mysecret secret is mounted as a volume residing at /workspace/secret.
2
The myconfigmap config map is mounted as a volume residing at /workspace/configmap.

11.9.1.6. options

The options field enables you to modify Knative Service properties for the deployed function, such as autoscaling. If these options are not set, the default ones are used.

These options are available:

  • scale

    • min: The minimum number of replicas. Must be a non-negative integer. The default is 0.
    • max: The maximum number of replicas. Must be a non-negative integer. The default is 0, which means no limit.
    • metric: Defines which metric type is watched by the Autoscaler. It can be set to concurrency, which is the default, or rps.
    • target: Recommendation for when to scale up based on the number of concurrently incoming requests. The target option can be a float value greater than 0.01. The default is 100, unless the options.resources.limits.concurrency is set, in which case target defaults to its value.
    • utilization: Percentage of concurrent requests utilization allowed before scaling up. It can be a float value between 1 and 100. The default is 70.
  • resources

    • requests

      • cpu: A CPU resource request for the container with deployed function.
      • memory: A memory resource request for the container with deployed function.
    • limits

      • cpu: A CPU resource limit for the container with deployed function.
      • memory: A memory resource limit for the container with deployed function.
      • concurrency: Hard Limit of concurrent requests to be processed by a single replica. It can be integer value greater than or equal to 0, default is 0 - meaning no limit.

This is an example configuration of the scale options:

name: test
namespace: ""
runtime: go
...
options:
  scale:
    min: 0
    max: 10
    metric: concurrency
    target: 75
    utilization: 75
  resources:
    requests:
      cpu: 100m
      memory: 128Mi
    limits:
      cpu: 1000m
      memory: 256Mi
      concurrency: 100

11.9.1.7. image

The image field sets the image name for your function after it has been built. You can modify this field. If you do, the next time you run kn func build or kn func deploy, the function image will be created with the new name.

11.9.1.8. imageDigest

The imageDigest field contains the SHA256 hash of the image manifest when the function is deployed. Do not modify this value.

11.9.1.9. labels

The labels field enables you to set labels on a deployed function.

You can set a label directly from a value. In the following example, the label with the role key is directly assigned the value of backend:

labels:
- key: role
  value: backend

You can also set a label from a local environment variable. In the following example, the label with the author key is assigned the value of the USER local environment variable:

labels:
- key: author
  value: '{{ env:USER }}'

11.9.1.10. name

The name field defines the name of your function. This value is used as the name of your Knative service when it is deployed. You can change this field to rename the function on subsequent deployments.

11.9.1.11. namespace

The namespace field specifies the namespace in which your function is deployed.

11.9.1.12. runtime

The runtime field specifies the language runtime for your function, for example, python.

11.9.2. Referencing local environment variables from func.yaml fields

If you want to avoid storing sensitive information such as an API key in the function configuration, you can add a reference to an environment variable available in the local environment. You can do this by modifying the envs field in the func.yaml file.

Prerequisites

  • You need to have the function project created.
  • The local environment needs to contain the variable that you want to reference.

Procedure

  • To refer to a local environment variable, use the following syntax:

    {{ env:ENV_VAR }}

    Substitute ENV_VAR with the name of the variable in the local environment that you want to use.

    For example, you might have the API_KEY variable available in the local environment. You can assign its value to the MY_API_KEY variable, which you can then directly use within your function:

    Example function

    name: test
    namespace: ""
    runtime: go
    ...
    envs:
    - name: MY_API_KEY
      value: '{{ env:API_KEY }}'
    ...

11.9.3. Additional resources

11.10. Accessing secrets and config maps from functions

After your functions have been deployed to the cluster, they can access data stored in secrets and config maps. This data can be mounted as volumes, or assigned to environment variables. You can configure this access interactively by using the Knative CLI, or by manually by editing the function configuration YAML file.

Important

To access secrets and config maps, the function must be deployed on the cluster. This functionality is not available to a function running locally.

If a secret or config map value cannot be accessed, the deployment fails with an error message specifying the inaccessible values.

11.10.1. Modifying function access to secrets and config maps interactively

You can manage the secrets and config maps accessed by your function by using the kn func config interactive utility. The available operations include listing, adding, and removing values stored in config maps and secrets as environment variables, as well as listing, adding, and removing volumes. This functionality enables you to manage what data stored on the cluster is accessible by your function.

Prerequisites

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

Procedure

  1. Run the following command in the function project directory:

    $ kn func config

    Alternatively, you can specify the function project directory using the --path or -p option.

  2. Use the interactive interface to perform the necessary operation. For example, using the utility to list configured volumes produces an output similar to this:

    $ kn func config
    ? What do you want to configure? Volumes
    ? What operation do you want to perform? List
    Configured Volumes mounts:
    - Secret "mysecret" mounted at path: "/workspace/secret"
    - Secret "mysecret2" mounted at path: "/workspace/secret2"

    This scheme shows all operations available in the interactive utility and how to navigate to them:

    kn func config
       ├─> Environment variables
       │               ├─> Add
       │               │    ├─> ConfigMap: Add all key-value pairs from a config map
       │               │    ├─> ConfigMap: Add value from a key in a config map
       │               │    ├─> Secret: Add all key-value pairs from a secret
       │               │    └─> Secret: Add value from a key in a secret
       │               ├─> List: List all configured environment variables
       │               └─> Remove: Remove a configured environment variable
       └─> Volumes
               ├─> Add
               │    ├─> ConfigMap: Mount a config map as a volume
               │    └─> Secret: Mount a secret as a volume
               ├─> List: List all configured volumes
               └─> Remove: Remove a configured volume
  3. Optional. Deploy the function to make the changes take effect:

    $ kn func deploy -p test

11.10.2. Modifying function access to secrets and config maps interactively by using specialized commands

Every time you run the kn func config utility, you need to navigate the entire dialogue to select the operation you need, as shown in the previous section. To save steps, you can directly execute a specific operation by running a more specific form of the kn func config command:

  • To list configured environment variables:

    $ kn func config envs [-p <function-project-path>]
  • To add environment variables to the function configuration:

    $ kn func config envs add [-p <function-project-path>]
  • To remove environment variables from the function configuration:

    $ kn func config envs remove [-p <function-project-path>]
  • To list configured volumes:

    $ kn func config volumes [-p <function-project-path>]
  • To add a volume to the function configuration:

    $ kn func config volumes add [-p <function-project-path>]
  • To remove a volume from the function configuration:

    $ kn func config volumes remove [-p <function-project-path>]

11.10.3. Adding function access to secrets and config maps manually

You can manually add configuration for accessing secrets and config maps to your function. This might be preferable to using the kn func config interactive utility and commands, for example when you have an existing configuration snippet.

11.10.3.1. Mounting a secret as a volume

You can mount a secret as a volume. Once a secret is mounted, you can access it from the function as a regular file. This enables you to store on the cluster data needed by the function, for example, a list of URIs that need to be accessed by the function.

Prerequisites

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

Procedure

  1. Open the func.yaml file for your function.
  2. For each secret you want to mount as a volume, add the following YAML to the volumes section:

    name: test
    namespace: ""
    runtime: go
    ...
    volumes:
    - secret: mysecret
      path: /workspace/secret
    • Substitute mysecret with the name of the target secret.
    • Substitute /workspace/secret with the path where you want to mount the secret.

      For example, to mount the addresses secret, use the following YAML:

      name: test
      namespace: ""
      runtime: go
      ...
      volumes:
      - configMap: addresses
        path: /workspace/secret-addresses
  3. Save the configuration.

11.10.3.2. Mounting a config map as a volume

You can mount a config map as a volume. Once a config map is mounted, you can access it from the function as a regular file. This enables you to store on the cluster data needed by the function, for example, a list of URIs that need to be accessed by the function.

Prerequisites

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

Procedure

  1. Open the func.yaml file for your function.
  2. For each config map you want to mount as a volume, add the following YAML to the volumes section:

    name: test
    namespace: ""
    runtime: go
    ...
    volumes:
    - configMap: myconfigmap
      path: /workspace/configmap
    • Substitute myconfigmap with the name of the target config map.
    • Substitute /workspace/configmap with the path where you want to mount the config map.

      For example, to mount the addresses config map, use the following YAML:

      name: test
      namespace: ""
      runtime: go
      ...
      volumes:
      - configMap: addresses
        path: /workspace/configmap-addresses
  3. Save the configuration.

11.10.3.3. Setting environment variable from a key value defined in a secret

You can set an environment variable from a key value defined as a secret. A value previously stored in a secret can then be accessed as an environment variable by the function at runtime. This can be useful for getting access to a value stored in a secret, such as the ID of a user.

Prerequisites

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

Procedure

  1. Open the func.yaml file for your function.
  2. For each value from a secret key-value pair that you want to assign to an environment variable, add the following YAML to the envs section:

    name: test
    namespace: ""
    runtime: go
    ...
    envs:
    - name: EXAMPLE
      value: '{{ secret:mysecret:key }}'
    • Substitute EXAMPLE with the name of the environment variable.
    • Substitute mysecret with the name of the target secret.
    • Substitute key with the key mapped to the target value.

      For example, to access the user ID that is stored in userdetailssecret, use the following YAML:

      name: test
      namespace: ""
      runtime: go
      ...
      envs:
      - value: '{{ configMap:userdetailssecret:userid }}'
  3. Save the configuration.

11.10.3.4. Setting environment variable from a key value defined in a config map

You can set an environment variable from a key value defined as a config map. A value previously stored in a config map can then be accessed as an environment variable by the function at runtime. This can be useful for getting access to a value stored in a config map, such as the ID of a user.

Prerequisites

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

Procedure

  1. Open the func.yaml file for your function.
  2. For each value from a config map key-value pair that you want to assign to an environment variable, add the following YAML to the envs section:

    name: test
    namespace: ""
    runtime: go
    ...
    envs:
    - name: EXAMPLE
      value: '{{ configMap:myconfigmap:key }}'
    • Substitute EXAMPLE with the name of the environment variable.
    • Substitute myconfigmap with the name of the target config map.
    • Substitute key with the key mapped to the target value.

      For example, to access the user ID that is stored in userdetailsmap, use the following YAML:

      name: test
      namespace: ""
      runtime: go
      ...
      envs:
      - value: '{{ configMap:userdetailsmap:userid }}'
  3. Save the configuration.

11.10.3.5. Setting environment variables from all values defined in a secret

You can set an environment variable from all values defined in a secret. Values previously stored in a secret can then be accessed as environment variables by the function at runtime. This can be useful for simultaneously getting access to a collection of values stored in a secret, for example, a set of data pertaining to a user.

Prerequisites

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

Procedure

  1. Open the func.yaml file for your function.
  2. For every secret for which you want to import all key-value pairs as environment variables, add the following YAML to the envs section:

    name: test
    namespace: ""
    runtime: go
    ...
    envs:
    - value: '{{ secret:mysecret }}' 1
    1
    Substitute mysecret with the name of the target secret.

    For example, to access all user data that is stored in userdetailssecret, use the following YAML:

    name: test
    namespace: ""
    runtime: go
    ...
    envs:
    - value: '{{ configMap:userdetailssecret }}'
  3. Save the configuration.

11.10.3.6. Setting environment variables from all values defined in a config map

You can set an environment variable from all values defined in a config map. Values previously stored in a config map can then be accessed as environment variables by the function at runtime. This can be useful for simultaneously getting access to a collection of values stored in a config map, for example, a set of data pertaining to a user.

Prerequisites

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

Procedure

  1. Open the func.yaml file for your function.
  2. For every config map for which you want to import all key-value pairs as environment variables, add the following YAML to the envs section:

    name: test
    namespace: ""
    runtime: go
    ...
    envs:
    - value: '{{ configMap:myconfigmap }}' 1
    1
    Substitute myconfigmap with the name of the target config map.

    For example, to access all user data that is stored in userdetailsmap, use the following YAML:

    name: test
    namespace: ""
    runtime: go
    ...
    envs:
    - value: '{{ configMap:userdetailsmap }}'
  3. Save the file.

11.11. Adding annotations to functions

You can add Kubernetes annotations to a deployed Serverless function. Annotations enable you to attach arbitrary metadata to a function, for example, a note about the function’s purpose. Annotations are added to the annotations section of the func.yaml configuration file.

There are two limitations of the function annotation feature:

  • After a function annotation propagates to the corresponding Knative service on the cluster, it cannot be removed from the service by deleting it from the func.yaml file. You must remove the annotation from the Knative service by modifying the YAML file of the service directly, or by using the OpenShift Dedicated web console.
  • You cannot set annotations that are set by Knative, for example, the autoscaling annotations.

11.11.1. Adding annotations to a function

You can add annotations to a function. Similar to a label, an annotation is defined as a key-value map. Annotations are useful, for example, for providing metadata about a function, such as the function’s author.

Prerequisites

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

Procedure

  1. Open the func.yaml file for your function.
  2. For every annotation that you want to add, add the following YAML to the annotations section:

    name: test
    namespace: ""
    runtime: go
    ...
    annotations:
      <annotation_name>: "<annotation_value>" 1
    1
    Substitute <annotation_name>: "<annotation_value>" with your annotation.

    For example, to indicate that a function was authored by Alice, you might include the following annotation:

    name: test
    namespace: ""
    runtime: go
    ...
    annotations:
      author: "alice@example.com"
  3. Save the configuration.

The next time you deploy your function to the cluster, the annotations are added to the corresponding Knative service.

11.12. Functions development reference guide

Important

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/.

OpenShift Serverless Functions provides templates that can be used to create basic functions. A template initiates the function project boilerplate and prepares it for use with the kn func tool. Each function template is tailored for a specific runtime and follows its conventions. With a template, you can initiate your function project automatically.

Templates for the following runtimes are available:

11.12.1. Node.js context object reference

The context object has several properties that can be accessed by the function developer. Accessing these properties can provide information about HTTP requests and write output to the cluster logs.

11.12.1.1. log

Provides a logging object that can be used to write output to the cluster logs. The log adheres to the Pino logging API.

Example log

function handle(context) {
  context.log.info(“Processing customer”);
}

You can access the function by using the kn func invoke command:

Example command

$ kn func invoke --target 'http://example.function.com'

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"Processing customer"}

You can change the log level to one of fatal, error, warn, info, debug, trace, or silent. To do that, change the value of logLevel by assigning one of these values to the environment variable FUNC_LOG_LEVEL using the config command.

11.12.1.2. query

Returns the query string for the request, if any, as key-value pairs. These attributes are also found on the context object itself.

Example query

function handle(context) {
  // Log the 'name' query parameter
  context.log.info(context.query.name);
  // Query parameters are also attached to the context
  context.log.info(context.name);
}

You can access the function by using the kn func invoke command:

Example command

$ kn func invoke --target 'http://example.com?name=tiger'

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"tiger"}

11.12.1.3. body

Returns the request body if any. If the request body contains JSON code, this will be parsed so that the attributes are directly available.

Example body

function handle(context) {
  // log the incoming request body's 'hello' parameter
  context.log.info(context.body.hello);
}

You can access the function by using the curl command to invoke it:

Example command

$ kn func invoke -d '{"Hello": "world"}'

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"world"}

11.12.1.4. headers

Returns the HTTP request headers as an object.

Example header

function handle(context) {
  context.log.info(context.headers["custom-header"]);
}

You can access the function by using the kn func invoke command:

Example command

$ kn func invoke --target 'http://example.function.com'

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"some-value"}

11.12.1.5. HTTP requests

method
Returns the HTTP request method as a string.
httpVersion
Returns the HTTP version as a string.
httpVersionMajor
Returns the HTTP major version number as a string.
httpVersionMinor
Returns the HTTP minor version number as a string.

11.12.2. TypeScript context object reference

The context object has several properties that can be accessed by the function developer. Accessing these properties can provide information about incoming HTTP requests and write output to the cluster logs.

11.12.2.1. log

Provides a logging object that can be used to write output to the cluster logs. The log adheres to the Pino logging API.

Example log

export function handle(context: Context): string {
    // log the incoming request body's 'hello' parameter
    if (context.body) {
      context.log.info((context.body as Record<string, string>).hello);
    } else {
      context.log.info('No data received');
    }
    return 'OK';
}

You can access the function by using the kn func invoke command:

Example command

$ kn func invoke --target 'http://example.function.com'

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"Processing customer"}

You can change the log level to one of fatal, error, warn, info, debug, trace, or silent. To do that, change the value of logLevel by assigning one of these values to the environment variable FUNC_LOG_LEVEL using the config command.

11.12.2.2. query

Returns the query string for the request, if any, as key-value pairs. These attributes are also found on the context object itself.

Example query

export function handle(context: Context): string {
      // log the 'name' query parameter
    if (context.query) {
      context.log.info((context.query as Record<string, string>).name);
    } else {
      context.log.info('No data received');
    }
    return 'OK';
}

You can access the function by using the kn func invoke command:

Example command

$ kn func invoke --target 'http://example.function.com' --data '{"name": "tiger"}'

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"tiger"}
{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"tiger"}

11.12.2.3. body

Returns the request body, if any. If the request body contains JSON code, this will be parsed so that the attributes are directly available.

Example body

export function handle(context: Context): string {
    // log the incoming request body's 'hello' parameter
    if (context.body) {
      context.log.info((context.body as Record<string, string>).hello);
    } else {
      context.log.info('No data received');
    }
    return 'OK';
}

You can access the function by using the kn func invoke command:

Example command

$ kn func invoke --target 'http://example.function.com' --data '{"hello": "world"}'

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"world"}

11.12.2.4. headers

Returns the HTTP request headers as an object.

Example header

export function handle(context: Context): string {
    // log the incoming request body's 'hello' parameter
    if (context.body) {
      context.log.info((context.headers as Record<string, string>)['custom-header']);
    } else {
      context.log.info('No data received');
    }
    return 'OK';
}

You can access the function by using the curl command to invoke it:

Example command

$ curl -H'x-custom-header: some-value’' http://example.function.com

Example output

{"level":30,"time":1604511655265,"pid":3430203,"hostname":"localhost.localdomain","reqId":1,"msg":"some-value"}

11.12.2.5. HTTP requests

method
Returns the HTTP request method as a string.
httpVersion
Returns the HTTP version as a string.
httpVersionMajor
Returns the HTTP major version number as a string.
httpVersionMinor
Returns the HTTP minor version number as a string.