Creating a NATS Super Cluster in Digital Ocean with Helm

Let's create a super cluster using NATS Gateways. First let's create 3 different clusters in NYC, Amsterdam, and San Francisco:

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, open up the firewall across the 3 regions to be able to access the client, leafnode and gateways ports:

for firewall in `doctl compute firewall list | tail -n 3 | awk '{print $1}'`; do
doctl compute firewall add-rules $firewall --inbound-rules protocol:tcp,ports:4222,address:0.0.0.0/0
doctl compute firewall add-rules $firewall --inbound-rules protocol:tcp,ports:7422,address:0.0.0.0/0
doctl compute firewall add-rules $firewall --inbound-rules protocol:tcp,ports:7522,address:0.0.0.0/0
done

For this setup, we will create a super cluster using the external IPs from the nodes of the 3 clusters. For a production type of setup, it is recommended to use a DNS entry and an A record for each one of the servers.

for ctx in do-ams3-nats-k8s-ams3 do-nyc1-nats-k8s-nyc1 do-sfo2-nats-k8s-sfo2; do
echo "name: $ctx"
for externalIP in `kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="ExternalIP")].address}'`; do
echo "- nats://$externalIP:7522";
done
echo
done

The Helm definition would look as follows for the 3 clusters:

# super-cluster.yaml
nats:
externalAccess: true
logging:
debug: false
trace: false
cluster:
enabled: true
gateway:
enabled: true
# NOTE: defined via --set gateway.name="$ctx"
# name: $ctx
gateways:
- name: do-ams3-nats-k8s-ams3
urls:
- nats://142.93.251.181:7522
- nats://161.35.12.245:7522
- nats://161.35.2.153:7522
- name: do-nyc1-nats-k8s-nyc1
urls:
- nats://142.93.251.181:7522
- nats://161.35.12.245:7522
- nats://161.35.2.153:7522
- name: do-sfo2-nats-k8s-sfo2
urls:
- nats://142.93.251.181:7522
- nats://161.35.12.245:7522
- nats://161.35.2.153:7522
natsbox:
enabled: true

Let's deploy the super cluster with Helm using the name of cluster as the name of the gateway:

for ctx in do-ams3-nats-k8s-ams3 do-nyc1-nats-k8s-nyc1 do-sfo2-nats-k8s-sfo2; do
helm --kube-context $ctx install nats nats/nats -f super-cluster.yaml --set gateway.name=$ctx
done

That's it! It should now be possible to send some messages across regions:

# Start subscription in Amsterdam
nats-box:~# kubectl --context do-ams3-nats-k8s-ams3 exec -it nats-box -- /bin/sh -l
nats-box:~# nats-sub -s nats hello
# Send messages from San Francisco region
nats-box:~# kubectl --context do-sfo2-nats-k8s-sfo2 exec -it nats-box -- /bin/sh -l
nats-box:~# nats-pub -s nats hello 'Hello World!'
# From outside of k8s can use the external IPs
$ nats-sub -s 142.93.251.181 hello
$ nats-pub -s 161.35.2.153 hello 'Hello World!'