Kube-vip services

We've designed kube-vip to be as de-coupled or agnostic from other components that may exist within a Kubernetes cluster as possible. This has lead to kube-vip having a very simplistic but robust approach to advertising Kubernetes services to the outside world and marking these services as ready to use.

Flow

This section details the flow of events in order for kube-vip to advertise a Kubernetes service:

An end user exposes a application through Kubernetes as a LoadBalancer => kubectl expose deployment nginx-deployment --port=80 --type=LoadBalancer --name=nginx
Within the Kubernetes cluster a service object is created with the svc.Spec.Type = ServiceTypeLoadBalancer
A controller (typically a Cloud Controller) has a loop that "watches" for services of the type LoadBalancer.
The controller now has the responsibility of providing an IP address for this service along with doing anything that is network specific for the environment where the cluster is running.
Once the controller has an IP address it will update the service svc.Spec.LoadBalancerIP with it's new IP address.
The kube-vip pods also implement a "watcher" for services that have a svc.Spec.LoadBalancerIP address attached.
When a new service appears kube-vip will start advertising this address to the wider network (through BGP/ARP) which will allow traffic to come into the cluster and hit the service network.
Finally kube-vip will update the service status so that the API reflects that this LoadBalancer is ready. This is done by updating the svc.Status.LoadBalancer.Ingress with the VIP address.

CCM

We can see from the flow above that kube-vip isn't coupled to anything other than the Kubernetes API, and will only act upon an existing Kubernetes primative (in this case the object of type Service). This makes it easy for exist CCMs to simply apply their logic to services of type LoadBalancer and leave kube-vip to take the next steps to advertise these load-balancers to the outside world.

The below instructions should just work on Kubernetes regardless of architecture, Linux as the Operating System is the only requirement.

Using the Plunder Cloud Provider (CCM)

If you just want things to "work", then you can quickly install the "latest" components:

**Install the plndr-cloud-provider

kubectl apply -f https://kube-vip.io/manifests/controller.yaml

Create the cidr for the global namespace

kubectl create configmap --namespace kube-system plndr --from-literal cidr-global=192.168.0.200/29

Creating services of type: LoadBalancer in the default namespace will now take addresses from the global cidr defined in the configmap.

Additional namespaces

Edit the configmap and add in the cidr ranges for those namespaces, the key in the cidr should be cidr-<namespace>, then ensure that kube-vip is deployed into that namespac e with the above apply command with the -n namespace flag.

The Detailed guide

Deploy the `plndr-cloud-provider`

To deploy the [latest] then kubectl apply -f https://kube-vip.io/manifests/controller.yaml, specific versions should be found in the repository as detailed below:

From the GitHub repository https://github.com/plunder-app/plndr-cloud-provider/tree/master/example/pod, find the version of the plunder cloud provider manifest (although typically the highest version number will provider more functionality/stability). The [raw] option in Githu b will provide the url that can be applied directly with a kubectl apply -f <url>.

The following output should appear when the manifest is applied:

serviceaccount/plunder-cloud-controller created
clusterrole.rbac.authorization.k8s.io/system:plunder-cloud-controller-role created
clusterrolebinding.rbac.authorization.k8s.io/system:plunder-cloud-controller-binding created
pod/plndr-cloud-provider created

We can validate the cloud-provider by examining the pods:

kubectl logs -n kube-system plndr-cloud-provider-0 -f

The `plndr-cloud-provider` `configmap`

The configmap details a CIDR range per namespace, however as of (kube-vip 0.2.1 and plnder-cloud-provider 0.1.4), there is now the option of having a global CIDR rang e (cidr-global).

To manage the ranges for the load-balancer instances, the plndr-cloud-provider has a configmap held in the kube-system namespace. The structure for the key/values within th e configmap should be that the key is in the format cidr-<namespace> and the value should be the cidr range.

Example Configmap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: plndr
  namespace: kube-system
data:
  cidr-default: 192.168.0.200/29
  cidr-global: 192.168.0.210/29

Expose a service

We can now expose a service and once the cloud provider has provided an address kube-vip will start to advertise that address to the outside world as shown below!

kubectl expose deployment nginx-deployment --port=80 --type=LoadBalancer --name=nginx

We can also expose a specific address by specifying it on the command line:

kubectl expose deployment nginx-deployment --port=80 --type=LoadBalancer --name=nginx --load-balancer-ip=1.1.1.1

Using DHCP for Load Balancers (experimental)

With the latest release of kube-vip > 0.2.1, it is possible to use the local network DHCP server to provide kube-vip with a load-balancer address that can be used to access a Kubernetes service on the network.

In order to do this we need to signify to kube-vip and the cloud-provider that we don't need one of their managed addresses. We do this by explicitly exposing a service on the address 0.0.0.0. When kube-vip sees a service on this address it will create a macvlan interface on the host and request a DHCP address, once this address is provided it wi ll assign it as the VIP and update the Kubernetes service!

$ k expose deployment nginx-deployment --port=80 --type=LoadBalancer --name=nginx-dhcp --load-balancer-ip=0.0.0.0; k get svc
service/nginx-dhcp exposed
NAME         TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)        AGE
kubernetes   ClusterIP      10.96.0.1       <none>          443/TCP        17m
nginx-dhcp   LoadBalancer   10.97.150.208   0.0.0.0         80:31184/TCP   0s

{ ... a second or so later ... }

$ k get svc
NAME         TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)        AGE
kubernetes   ClusterIP      10.96.0.1       <none>          443/TCP        17m
nginx-dhcp   LoadBalancer   10.97.150.208   192.168.0.155   80:31184/TCP   3s

Using UPNP to expose a service to the outside world

With the latest release of kube-vip > 0.2.1, it is possible to expose a load-balancer on a specific port and using UPNP (on a supported gateway) expose this service to the inte rnet.

Most simple networks look something like the following:

<----- <internal network 192.168.0.0/24> <Gateway / router> <external network address> ----> Internet

Using UPNP we can create a matching port on the <external network address> allowing your service to be exposed to the internet.

Enable UPNP

Add the following to the kube-vip env: section, and the rest should be completely automated.

Note some environments may require (Unifi) will require Secure mode being disabled (this allows a host with a different address to register a port)

- name: enableUPNP
  value: "true"

Exposing a service

To expose a port successfully we'll need to change the command slightly:

--target-port=80 the port of the application in the pods (HTT/NGINX) --port=32380 the port the service will be exposed on (and what you should connect to in order to receive traffic from the service)

kubectl expose deployment plunder-nginx --port=32380 --target-port=80 --type=LoadBalancer --namespace plunder

The above example should expose a port on your external (internet facing address), that can be tested externally with:

$ curl externalIP:32380
<!DOCTYPE html>
<html>
...

Expose with packet (using the `plndr-cloud-provider`)

Either through the CLI or through the UI, create a public IPv4 EIP address.. and this is the address you can expose through BGP!

# packet ip request -p xxx-bbb-ccc -f ams1 -q 1 -t public_ipv4                                                                   
+-------+---------------+--------+----------------------+
|   ID  |    ADDRESS    | PUBLIC |       CREATED        |
+-------+---------------+--------+----------------------+
| xxxxx |     1.1.1.1   | true   | 2020-11-10T15:57:39Z |
+-------+---------------+--------+----------------------+

kubectl expose deployment nginx-deployment --port=80 --type=LoadBalancer --name=nginx --load-balancer-ip=1.1.1.1