Using a Load Balancer for External Access to NATS

Using a Load Balancer for External Access to NATS

In the example below, you can find how to use an AWS Network Load Balancer to connect externally to a cluster that has TLS setup.

One-line installer creates a secure cluster named ‘nats’

  1. curl -sSL https://nats-io.github.io/k8s/setup.sh | sh

Create AWS Network Load Balancer service

  1. echo '
  2. apiVersion: v1
  3. kind: Service
  4. metadata:
  5.   name: nats-nlb
  6.   namespace: default
  7.   labels:
  8.     app: nats
  9.   annotations:
  10.     service.beta.kubernetes.io/aws-load-balancer-type: "nlb"
  11. spec:
  12.   type: LoadBalancer
  13.   externalTrafficPolicy: Local
  14.   ports:
  15.   - name: nats
  16.     port: 4222
  17.     protocol: TCP
  18.     targetPort: 4222
  19.   selector:
  20.     app.kubernetes.io/name: nats
  21. ' | kubectl apply -f -

Check that it worked

  1. kubectl get svc nats-nlb -o wide

Example output

  1. NAME       TYPE           CLUSTER-IP      EXTERNAL-IP                                                                     PORT(S)          AGE    SELECTOR
  2. nats-nlb   LoadBalancer   10.100.67.123   a18b60a948fc611eaa7840286c60df32-9e96a2af4b5675ec.elb.us-east-2.amazonaws.com   4222:30297/TCP   151m   app=nats

Publish a test message

  1. nats pub -s nats://a18b60a948fc611eaa7840286c60df32-9e96a2af4b5675ec.elb.us-east-2.amazonaws.com:4222 -creds nsc/nkeys/creds/KO/A/test.creds test.foo bar

Also, it would be recommended to set no_advertise to true in order to avoid gossiping internal addresses from pods in Kubernetes to NATS clients.

Setting up a NATS Server with external access on Azure

With the following, you can create a 3-node NATS Server cluster:

  1. kubectl apply -f https://raw.githubusercontent.com/nats-io/k8s/b55687a97a5fd55485e1af302fbdbe43d2d3b968/nats-server/leafnodes/nats-cluster.yaml

The configuration map from the NATS cluster that was created can be found below.

  1. ---
  2. apiVersion: v1
  3. kind: ConfigMap
  4. metadata:
  5.   name: nats-config
  6. data:
  7.   nats.conf: |
  8.     pid_file: "/var/run/nats/nats.pid"
  9.     http: 8222
  10.     # debug: true
  11.     ping_interval: 30s
  13.     cluster {
  14.       port: 6222
  15.       no_advertise: true
  17.       routes: [
  18.         nats://nats-0.nats.default.svc:6222
  19.         nats://nats-1.nats.default.svc:6222
  20.         nats://nats-2.nats.default.svc:6222
  21.       ]
  22.     }
  24.     leaf {
  25.       port: 7422
  26.       authorization {
  27.         timeout: 3s
  28.         users = [
  29.           { user: "foo", pass: "bar" }
  30.         ]
  31.       }
  32.     }

Now let’s expose the NATS Server by creating an L4 load balancer on Azure:

  1. kubectl apply -f https://raw.githubusercontent.com/nats-io/k8s/b55687a97a5fd55485e1af302fbdbe43d2d3b968/nats-server/leafnodes/lb.yaml

Confirm the public IP that was allocated to the nats-lb service that was created, in this case it is 52.155.49.45:

  1. kubectl get svc -o wide

Output

  1. NAME         TYPE           CLUSTER-IP    EXTERNAL-IP    PORT(S)                                                 AGE     SELECTOR
  2. kubernetes   ClusterIP      10.0.0.1      <none>         443/TCP                                                 81d     <none>
  3. nats         ClusterIP      None          <none>         4222/TCP,6222/TCP,8222/TCP,7777/TCP,7422/TCP,7522/TCP   7h46m   app=nats
  4. nats-lb      LoadBalancer   10.0.107.18   52.155.49.45   4222:31161/TCP,7422:30960/TCP                           7h40m   app=nats

Notice that the leafnode configuration requires authorization, so in order to connect to it we will need to configuration as follows:

  1. leaf {
  2.   remotes = [
  3.     {
  4.       url: "nats://foo:bar@52.155.49.45:7422"
  5.     }
  6.   ]
  7. }

You can also add a NATS Streaming cluster into the cluster connecting to the port 4222:

  1. kubectl apply -f https://raw.githubusercontent.com/nats-io/k8s/b55687a97a5fd55485e1af302fbdbe43d2d3b968/nats-server/leafnodes/stan-server.yaml

Now if you create two NATS Servers that connect to the same leafnode port, they will be able to receive messages to each other:

  1. nats-server -c leafnodes/leaf.conf -p 4222 &
  2. nats-server -c leafnodes/leaf.conf -p 4223 &

Create a subscriber and publish a test message

  1. nats sub -s localhost:4222 foo &
  2. nats pub -s localhost:4223 foo hello

Output

  1. Listening on [foo]
  2. [#1] Received on [foo] : 'hello'