Deploy Knative Functions - Container Service for Kubernetes

Knative Functions provides a simplified programming model for creating and deploying functions on Knative, abstracting Knative, Kubernetes, and container details. Create your function, let the platform build the container image, customize image build and deployment settings, and deploy it as a Knative Service.

Prerequisites

Make sure you have:

Knative is deployed in your ACK cluster. See Deploy and manage Knative.

Step 1: Install the func CLI

Download the func binary for your operating system from the func release page.

Example for Linux:

Rename the binary to func:
```
mv <path-to-binary-file> func
```
Replace <path-to-binary-file> with the downloaded binary path, such as func_linux_amd64.
Make the binary executable:
```
chmod +x func
```
Move the binary to a directory in your PATH:
```
mv func /usr/local/bin
```
Verify the installation:
```
func version
```
Version output confirms successful installation.

Step 2: Create a function

Knative Functions supports the following runtimes, all compatible with HTTP and CloudEvent invocations:

This example uses Go.

Create a function:

func create -l <language> <function-name>

Example: Create a Go function named hello:

func create -l go hello

Expected output:

Created go function in /usr/local/bin/hello

List the files in the hello directory:

ls hello/

Expected output:

func.yaml  go.mod  handle.go  handle_test.go  README.md

Review the generated func.yaml in the hello directory:

cat func.yaml

Expected output:

specVersion: 0.35.0
name: hello
runtime: go
created: 2023-12-13T06:48:45.419587147Z

Edit func.yaml to configure the registry and deployment settings. Complete example:

specVersion: 0.35.0
name: hello
runtime: go
created: 2023-11-29T14:47:34.101658+08:00
registry: registry.cn-beijing.aliyuncs.com/knative-release-xxx
image: registry.cn-beijing.aliyuncs.com/knative-release-xxx/hello:latest
build:
  builderImages:
    pack: registry-cn-beijing.ack.aliyuncs.com/acs/knative-func-builder-jammy-tiny:latest
deploy:
  namespace: default

Key fields:

Field	Description
`registry`	Container registry for built images. Example: `registry.cn-beijing.aliyuncs.com/knative-release-xxx`
`build.builderImages.pack`	Builder image for the function. Example: `registry-cn-beijing.ack.aliyuncs.com/acs/knative-func-builder-jammy-tiny:latest`
`deploy.namespace`	Target Kubernetes namespace for the function.

See the func.yaml reference for all available options.

Step 3: Deploy the function

Run func deploy from the hello directory. The command uses the project name as the Knative Service name and combines it with the registry to construct the image address.

func deploy

Expected output

Building function image
Still building
Still building
Yes, still building
Don't give up on me
Still building
This is taking a while
Still building
Still building
Yes, still building
Function built: registry.cn-beijing.aliyuncs.com/knative-release-xxx/hello:latest
Pushing function image to the registry "registry.cn-beijing.aliyuncs.com" using the "xxx" user credentials
Deploying function to the cluster
Function deployed in namespace "default" and exposed at URL:
   http://hello.default.example.com

Verify the deployment:

func info

Expected output:

Function name:
  hello
Function is built in image:

Function is deployed in namespace:
  default
Routes:
  http://hello.default.example.com

Step 4: Invoke the function

Add a hosts file entry to map the Knative Service domain to the gateway IP:
```
121.xx.xxx.xx hello.default.example.com
```
Replace 121.xx.xxx.xx with your Knative gateway IP and hello.default.example.com with your deployment domain.

Invoke the function:

func invoke

Expected output:

POST / HTTP/1.1 hello.default.example.com
  Content-Type: application/json
  Forwarded: for=192.168.102.101;proto=http
  Knative-Serving-Default-Route: true
  X-Forwarded-Proto: http
  User-Agent: Go-http-client/1.1
  Content-Length: 25
  Accept-Encoding: gzip
  K-Proxy-Request: activator
  X-Forwarded-For: 192.168.102.101, 192.168.102.97
  X-Request-Id: 3d82cfc8-f9df-4935-84cd-c6561b4587f6
Body:

The output confirms the function received and handled the HTTP request.

Verify that function pods were created:

kubectl get pod

Expected output:

NAME                                      READY   STATUS    RESTARTS   AGE
hello-00001-deployment-7b65fcdc4c-gfcbp   2/2     Running   0          34

Next steps

See Knative FAQ for common questions about Knative in ACK.