tomologic/kube2clouddns repository overview

⁠kube2clouddns

(short for Kubernetes Service To Google Cloud Platform Cloud DNS Sync Service)

⁠About

A Kubernetes app that keeps a service internal cluster ip in Kubernetes synced with a DNS record in a Google Cloud DNS zone.

This can be useful in the case where you are connected to the cluster network via VPN and still want to address the services via a public DNS server.

⁠Usage

kube2clouddns --help
Usage of kube2clouddns:
  -alsologtostderr
        log to standard error as well as files
  -domain string
        The domain that should host the service sub domains
  -kubeconfig string
        absolute path to a kubeconfig file
  -log_backtrace_at value
        when logging hits line file:N, emit a stack trace
  -log_dir string
        If non-empty, write log files in this directory
  -logtostderr
        log to standard error instead of files
  -project string
        The GCP project id in which the DNS zone for the domain is hosted
  -serviceaccount string
        absolute path to a service account json file
  -stderrthreshold value
        logs at or above this threshold go to stderr
  -v value
        log level for V logs
  -vmodule value
        comma-separated list of pattern=N settings for file-filtered logging

⁠Config

⁠Kubernetes API connection config

When running the application outside a kubernetes cluster a kube config has to supplied via command line argument. (ie ~/.kube/config)

When inside a cluster it will find the credentials from the kubelet.

⁠Service account for Cloud DNS authentication

For connection to Google Cloud DNS a service account credentials json file is needed. Outside of Kubernetes it can be supplied as argument. Inside kuberentes it has to be supplied as a secret.

To upload the secret to kubernetes, use this command

kubectl create secret generic clouddnsserviceaccount --from-file=clouddns_service_account.json

⁠Cloud DNS config

To parameters are needed to know what to update in Cloud DNS. The project id where a DNS zone exists that has the domain that should be updated. These two are given as arguments and can be injected via Kubernetes configmap as an example describes in deploy/clouddns_config.yaml

⁠Development

For quick turnaround in local development it's recommended to use a GO workspace according to the documentation: https://golang.org⁠

⁠Dependencies

To manage dependencies we use Glide, easily installed via:

curl https://glide.sh/get | sh

Install dependencies by

glide install

Add new dependencies

glide get github.com/foo/bar#^1.2.3

Dependencies can be viewed in the glide.yml file but the exact versions of depencencies are "locked down" in the glide.lock file.

⁠Test with minikube

Minikube is an excellent tool to try out this component. Install it and start it then run

eval $(minikube docker-env)

Upload test config and secrets to the test cluster by running

make upload-test-secret
make upload-test-config

The application can be started by

make deploy-test-kube2clouddns

And to test a test service (simple nginx container) can be deployed by

make deploy-test-service