Add guide to use Helm and leafnodes from scratch

nats-on-kubernetes/from-zero-to-leafnodes.md

@@ -0,0 +1,78 @@
+# From zero to communicating across K8S regions using NATS leafnodes
+
+First, we need a number of Kubernetes clusters to be setup already. In
+this case we'll create a few in Digital Ocean using the `doctl` tool but
+you could use any K8S solution available:
+
+```
+brew install doctl
+doctl kubernetes cluster create nats-k8s-nyc1 --count 3 --region nyc1
+doctl kubernetes cluster create nats-k8s-sfo2 --count 3 --region sfo2
+doctl kubernetes cluster create nats-k8s-ams3 --count 3 --region ams3
+```
+
+Next, get your NGS credentials with leafnodes enabled.  For this follow the instructions at: https://synadia.com/ngs/signup
+Once you got the credentials, upload them as a secret to your K8S clusters:
+
+```sh
+for ctx in do-ams3-nats-k8s-ams3 do-nyc1-nats-k8s-nyc1 do-sfo2-nats-k8s-sfo2; do
+  kubectl --context $ctx create secret generic ngs-creds --from-file $HOME/.nkeys/creds/synadia/NGS/NGS.creds
+done
+```
+
+Install Helm3 and add the NATS helm chart repo:
+
+```
+brew install helm
+helm repo add nats https://nats-io.github.io/k8s/helm/charts/
+helm repo update
+```
+
+Create the config that adds the leafnode connection to NGS:
+
+```
+# nats.yaml
+leafnodes:
+  enabled: true
+  remotes:
+    - url: tls://connect.ngs.global:7422
+      credentials:
+        secret:
+          name: ngs-creds
+          key: NGS.creds
+natsbox:
+  enabled: true
+```
+
+Deploy it to your K8S regions:
+
+```sh
+for ctx in do-ams3-nats-k8s-ams3 do-nyc1-nats-k8s-nyc1 do-sfo2-nats-k8s-sfo2; do
+  helm --kube-context $ctx install nats nats/nats -f nats.yaml
+done
+```
+
+To test the multi-region connectivity by using the `nats-box` container that got deployed in each cluster:
+
+```
+kubectl --context do-ams3-nats-k8s-ams3  exec -it nats-box -- nats-sub -s nats hello
+Listening on [hello]
+
+while true; do
+  kubectl --context do-sfo2-nats-k8s-sfo2  exec -it nats-box -- nats-pub -s nats hello 'Hello World!'
+done
+```
+
+Results from the subscribe session:
+
+```
+[#1] Received on [hello]: 'Hello World!'
+[#2] Received on [hello]: 'Hello World!'
+[#3] Received on [hello]: 'Hello World!'
+[#4] Received on [hello]: 'Hello World!'
+[#5] Received on [hello]: 'Hello World!'
+[#6] Received on [hello]: 'Hello World!'
+[#7] Received on [hello]: 'Hello World!'
+[#8] Received on [hello]: 'Hello World!'
+[#9] Received on [hello]: 'Hello World!'
+```