Kotlin + HTTP4K + GraalVM + OpenFaaS Demonstration

Highly experimental: NOT FOR PRODUCTION USE (yet)

This is a demonstration that it is possible to write a simple serverless app using Kotlin and HTTP4K, creating a native binary using GraalVM and making it run on OpenFaaS using the incubating of-watchdog

The resulting static binary has a size of 6.5MB and the entire docker image has 19.2MB size in total.

Keep in mind, there are probably lots of things I haven't considered.

How to run it

1. Install OpenFaaS according to the documentation

   Hint: In case you are doing a local test like I did, e.g. in Docker for Mac, be sure to enable faasnetes.imagePullPolicy=IfNotPresent. Otherwise the functions won't start if they are not pushed to a docker registry.

2. Build the docker image containing the function and the watchdog

   docker build -t http4k_helloworld:0.0.1 .

   and push it to a registry that is available from your k8s cluster if necessary

3. Deploy the function to OpenFaas

   faas-cli deploy --gateway "$OPENFAAS_URL" --image http4k_helloworld:0.0.1 --name http4k-hello

   Output:

   Deployed. 202 Accepted.
   URL: $OPENFAAS_URL/function/http4k-example
   

4. Execute the deployed funtion

   curl -i "$OPENFAAS_URL/function/http4k-hello"

   Output:

   HTTP/1.1 200 OK
   Content-Length: 11
   Content-Type: text/plain; charset=utf-8
   Date: Fri, 26 Jul 2019 23:45:58 GMT
   Server: Apache-HttpCore/1.1
   X-Call-Id: ef81808e-3e30-4e9a-ae3c-664e3c54e269
   X-Duration-Seconds: 0.003135
   X-Start-Time: 1564184758245497900
   
   Hello World%