kevroletin / hs-knative-demo

hs-demo

This is a demo of using Knative using Haskell. It defines 4 services:

haskell-fn-events-ping
haskell-fn-events-pong
haskell-fn-serving-ping
haskell-fn-serving-pong

haskell-fn-events-ping and haskell-fn-events-pong can be called from outside of a cluster using HTTP Get requests. They send events to haskell-fn-serving-ping, haskell-fn-serving-pong event handlers. Event handlers just log received messaged.

Schematically it looks like that:

haskell-fn-events-ping -- Ping --> haskell-fn-serving-ping
haskell-fn-events-pong -- Pong --> haskell-fn-serving-pong

Messaging is done using Knative's exapmle-broker which comes with kn quickstart.

Build & Deploy

[Optional] Build docker images. This script will build executables locally and copy into docker images:

sh docker/build-images-from-local-exe.sh

This version builds everything inside of docker images docker/build-images.sh.

Deploy

kubectl apply -f knative.yaml

Watch logs

stern haskell-fn-events

Send events

curl http://haskell-fn-serving-pong.default.127.0.0.1.sslip.io
curl http://haskell-fn-serving-ping.default.127.0.0.1.sslip.io

Changes reconciliation

This is an open question. After any changes doing kubectl apply -f knative.yaml doesn't update services. My guess is that knative.yaml should contain version tags for images so that kubectl can understand that service configuration has changed.

For now, one needs to update services manually:

kn service update haskell-fn-serving-ping --image kevroletin/haskell-fn-serving-ping --port 8080
kn service update haskell-fn-serving-pong --image kevroletin/haskell-fn-serving-pong --port 8080
kn service update haskell-fn-events-ping --image kevroletin/haskell-fn-events-ping --port 8080
kn service update haskell-fn-events-pong --image kevroletin/haskell-fn-events-pong --port 8080