OpenWhisk Actions on Knative — Web Actions

This is a follow up blog post of How to run OpenWhisk actions on Knative?

In this blog post, we are going to experiment with OpenWhisk Web Action.

web-action.js

The main function in this action returns a JSON payload with headers, statusCode, and body which are passed along to the HTTP client while terminating the request/response. NodeJS runtime responds with the given status code if exists. Similarly, body is passed along as the body of the response. Content-Type in the header plays an important role in determining the type of body. The body is interpreted as application/json for non-string values and text/html otherwise in case Content-Type is not specified in action. When the Content-Type is defined in action body, the runtime checks if the response is binary data or plain text and decode the string using a base64 decoder if needed. An error is returned in case the body fails to decode.

Let’s try deploying this action on Knative:

Pre-requisites:

• Secret exists on Knative, check with:

$ kubectl get secret dockerhub-user-pass

• Service Account exists on Knative, check with:

$ kubectl get serviceaccount openwhisk-runtime-builder

• Build Template exists on Knative, check with:

$ kubectl get buildtemplate openwhisk-nodejs-runtime

If any of the secret/service account/build template does not exist on your Knative installation, please go back to the How to run OpenWhisk actions on Knative? blog post and run Step 1 through Step 3 depending on what’s missing.

Deploy NodeJS Runtime with Web Action

Configure the build file to point to your Docker Hub repo by replacing DOCKER_USERNAME with your username.

build.yaml

Deploy NodeJS runtime with action code:

$ kubectl apply -f build.yaml
build.build.knative.dev/nodejs-10-web-action created

Verify the build pod exists:

$ kubectl get build.build.knative.dev/nodejs-10-web-action
NAME                  SUCCEEDED   REASON   STARTTIME   COMPLETIONTIME
nodejs-10-web-action   True                 1m

Serve NodeJS Runtime as a Knative Service

Configure the service template to point to the Docker Hub repo where the OpenWhisk runtime (built in previous step) will be pulled from. Replace ${DOCKER_USERNAME} and create service.yaml:

service.yaml

Run Web Action

Depending on your Knative installation, determine how to access your knative gateway and run sequence of curl:

$ curl -H "Host: nodejs-web-action.default.example.com" -X POST http://<IP_ADDRESS>:<PORT>
{"OK":true}
$ curl -H "Host: nodejs-web-action.default.example.com" -X POST http://<IP_ADDRESS>:<PORT> > image.png

This action returns a very low resolution of OpenWhisk logo which was specified in the action.

image.png

We just saw a simple web action returning an image, NodeJS runtime support many more use cases including:

Hello World Web Action

web-action-hello.js

Web Action with HTTP Redirect

web-action-with-http-redirect.js

Web Action Setting a Cookie

web-action-set-a-cookie.js

Web Action Setting Multiple Cookies

web-action-set-multiple-cookies.js

All of these sample web actions are tested on OpenWhisk NodeJS Runtime.

Enjoy! 👍