canthefason / nats-operator

This operator manages NATS clusters atop Kubernetes, automating their creation and administration.

NATS Operator

NATS Operator manages NATS clusters atop Kubernetes, automating their creation and administration.

Requirements

• Kubernetes v1.8+

Getting Started

The current version of the operator creates a NatsCluster Custom Resources Definition (CRD) under the nats.io API group, to which you can make requests to create NATS clusters.

To add the NatsCluster and NATS Operator to your cluster you can run:

$ kubectl apply -f https://raw.githubusercontent.com/nats-io/nats-operator/master/example/deployment.yaml

You will then be able to confirm that there is a new CRD registered in the cluster:

$ kubectl get crd

NAME                                    AGE
natsclusters.nats.io                    1s

An example of creating a 3 node cluster is below. The NATS operator will be responsible of assembling the cluster and replacing pods in case of failures.

echo '
apiVersion: "nats.io/v1alpha2"
kind: "NatsCluster"
metadata:
  name: "example-nats-cluster"
spec:
  size: 3
  version: "1.1.0"
' | kubectl apply -f -

To list all the NATS clusters:

$ kubectl get natsclusters.nats.io

NAME                   AGE
example-nats-cluster   1s

RBAC support

If you have RBAC enabled (for example in GKE), you can run:

$ kubectl apply -f https://raw.githubusercontent.com/nats-io/nats-operator/master/example/deployment-rbac.yaml

Then this will deploy a nats-operator on the nats-io namespace.

$ kubectl -n nats-io logs deployment/nats-operator
time="2018-06-07T15:53:17-07:00" level=info msg="nats-operator Version: 0.2.2-v1alpha2+git"

Note that the NATS operator only monitors the NatsCluster resources which are created in the namespace where it was deployed, so if you want to create a cluster you have to specify the same one as the operator:

$ kubectl -n nats-io apply -f example/example-nats-cluster.yaml
natscluster "example-nats-1" created

$ kubectl -n nats-io get natsclusters
NAME             AGE
example-nats-1   6m

$ kubectl -n nats-io get pods -l nats_cluster=example-nats-1
NAME               READY     STATUS    RESTARTS   AGE
example-nats-1-1   1/1       Running   0          7m
example-nats-1-2   1/1       Running   0          7m
example-nats-1-3   1/1       Running   0          6m

TLS support

By using a pair of opaque secrets (one for the clients and then another for the routes), it is possible to set TLS for the communication between the clients and also for the transport between the routes:

apiVersion: "nats.io/v1alpha2"
kind: "NatsCluster"
metadata:
  name: "nats"
spec:
  # Number of nodes in the cluster
  size: 3
  version: "1.1.0"

  tls:
    # Certificates to secure the NATS client connections:
    serverSecret: "nats-clients-tls"

    # Certificates to secure the routes.
    routesSecret: "nats-routes-tls"

In order for TLS to be properly established between the nodes, it is necessary to create a wildcard certificate that matches the subdomain created for the service from the clients and the one for the routes.

The routesSecret has to provide the files: ca.pem, route-key.pem, route.pem, for the CA, server private and public key respectively.

$ kubectl create secret generic nats-routes-tls --from-file=ca.pem --from-file=route-key.pem --from-file=route.pem

Similarly, the serverSecret has to provide the files: ca.pem, server-key.pem, and server.pem for the CA, server private key and public key used to secure the connection with the clients.

$ kubectl create secret generic nats-clients-tls --from-file=ca.pem --from-file=server-key.pem --from-file=server.pem

Authorization

Authorization can be set for the server by using a secret where the permissions are defined in JSON:

{
  "users": [
    { "username": "user1", "password": "secret1" },
    { "username": "user2", "password": "secret2",
      "permissions": {
	"publish": ["hello.*"],
	"subscribe": ["hello.world"]
      }
    }
  ],
  "default_permissions": {
    "publish": ["SANDBOX.*"],
    "subscribe": ["PUBLIC.>"]
  }
}

Example of creating a secret to set the permissions:

kubectl create secret generic nats-clients-auth --from-file=clients-auth.json

Now when creating a NATS cluster it is possible to set the permissions as in the following example:

apiVersion: "nats.io/v1alpha2"
kind: "NatsCluster"
pmetadata:
  name: "example-nats-auth"
spec:
  size: 3
  version: "1.1.0"

  auth:
    # Definition in JSON of the users permissions
    clientsAuthSecret: "nats-clients-auth"

    # How long to wait for authentication
    clientsAuthTimeout: 5

Configuration Reload

On Kubernetes +v1.10 clusters that have been started with support for sharing the process namespace (via --feature-gates=PodShareProcessNamespace=true), it is possible to enable on-the-fly reloading of configuration for the servers that are part of the cluster. This can also be combined with the authorization support, so in case the user permissions change, then the servers will reload and apply the new permissions.

apiVersion: "nats.io/v1alpha2"
kind: "NatsCluster"
metadata:
  name: "example-nats-auth"
spec:
  size: 3
  version: "1.1.0"

  pod:
    # Enable on-the-fly NATS Server config reload
    # Note: only supported in Kubernetes clusters with PID namespace sharing enabled.
    enableConfigReload: true

    # Possible to customize version of reloader image
    reloaderImage: connecteverything/nats-server-config-reloader"
    reloaderImageTag: "0.2.2-v1alpha2"
    reloaderImagePullPolicy: "IfNotPresent"
  auth:
    # Definition in JSON of the users permissions
    clientsAuthSecret: "nats-clients-auth"

    # How long to wait for authentication
    clientsAuthTimeout: 5

Development

Building the Docker Image

To build the nats-operator Docker image:

$ docker build -t <image>:<tag> .

You'll need Docker 17.06.0-ce or higher.

Updating the NatsCluster type (code generation)

If you are adding a new field to the NatsCluster, then you have to get the deepcopy-gen tools first.

$ go get -u github.com/kubernetes/gengo/examples/deepcopy-gen

Then run the code generation script in order to recreate pkg/spec/zz_generated.deepcopy.go with the required methods to support that field filled in:

$ ./hack/codegen.sh

Running outside the cluster for debugging

For debugging purposes, it is also possible to run the operator outside of the cluster without having to build an image:

MY_POD_NAMESPACE=default MY_POD_NAME=nats-operator go run cmd/operator/main.go --debug-kube-config-path=$HOME/.kube/config