go-cfgwatch

README

go-cfgwatch

Go based Kubernetes app - Watches for ConfigMap changes and soft recycles the business logic

Purpose:

Watching a loaded configuration map and on change trigger a soft restart of the business logic which is running in a Go routine.

Info:

In this case the logic is a web server running in a Go Routine which is reading a value from memory and then outputting it when called.

Takeaway:

The business logic is running in a Go routine and its execution and termination are handled by a simple supervisor routine in the main function that is triggered(stop/restart) by the file watcher function which is also running in its own Go routine. This approach is most effective with stateless applications. State full application would require additional logic to ensure all writes are complete prior to restart, however this should not be difficult to achieve.

Rebuild

git clone repo
go mod tidy
env GOOS=linux GOARCH=amd64 go build -o app main.go
docker build -t go-cfgwatch .
docker tag go-cfgwatch <repo>/go-cfgwatch
docker push <repo>/go-cfgwatch

edit go-op-rc.yaml (update repo)
kubectl apply -f configmap.yaml -n default
kubectl apply -f go-op-rc.yaml -n default

Run As

git clone repo
kubectl apply -f configmap.yaml -n default
kubectl apply -f go-op-rc.yaml -n default

Testing

Tail Pod Logs and/or expose via SVC and access with browser
Update Config Map
Watch for Change. 

Example Output

Documentation

Overview

Note: the example only works with the code within the same release/branch.