Virtual Geek

The intent of this Load balancer is to spread the workload among different servers or applications. It can be set up on both physical and virtual infrastructures. The load balancer traces the accessibility and availability of pods with the Kubernetes Endpoints API. When it gets an app request for a certain Kubernetes service, the Kubernetes load balancer sorts in order or round robins the application request among appropriate Kubernetes pods for the service.

Here are two kinds of load balancers:

L4 load balancers, or else known as network load balancers
They handle layer 4 data that is present at the network and transport (TCP/UDP) level. These load balancers do not aim on application knowledge, such as content type, cookies, header location, etc. This way they will only transmit traffic built on network layer data.

L7 load balancers, otherwise famously known as application load balancers
Unlike L4 load balancers, this kind of load balancer redirects traffic by utilizing the application layer configuration. These load balancers manage a greater amount of data, and are built on more information. This involves HTTP, HTTPS and SSL protocols, for example.

In earlier article I configured Kubernetes Ingress Controller Setup and deploy Ingress controller for Kubernetes on Bare Metal servers

At this moment while writing this blog, MetalLB application product is the only Load Balancer supported for Bare Metal Kubernetes Cluster. When you use a Load Balancer type Kubernetes Service on Cloud, Cloud providers deploy their own Load Balancer resource for Kubernetes services in the cloud.

To deploy MetalLB Load Balancer in Kubernetes Cluster you can found instructions from https://metallb.universe.tf/. Use below github url to deploy Kubernetes resources and custom resource definition (crds) in the cluster.

ubuntu@k8smaster01:~$ sudo su -
root@k8smaster01:~#
root@k8smaster01:~# kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.13.7/config/manifests/metallb-native.yaml
namespace/metallb-system created
customresourcedefinition.apiextensions.k8s.io/addresspools.metallb.io created
customresourcedefinition.apiextensions.k8s.io/bfdprofiles.metallb.io created
customresourcedefinition.apiextensions.k8s.io/bgpadvertisements.metallb.io created
customresourcedefinition.apiextensions.k8s.io/bgppeers.metallb.io created
customresourcedefinition.apiextensions.k8s.io/communities.metallb.io created
customresourcedefinition.apiextensions.k8s.io/ipaddresspools.metallb.io created
customresourcedefinition.apiextensions.k8s.io/l2advertisements.metallb.io created
serviceaccount/controller created
serviceaccount/speaker created
role.rbac.authorization.k8s.io/controller created
role.rbac.authorization.k8s.io/pod-lister created
clusterrole.rbac.authorization.k8s.io/metallb-system:controller created
clusterrole.rbac.authorization.k8s.io/metallb-system:speaker created
rolebinding.rbac.authorization.k8s.io/controller created
rolebinding.rbac.authorization.k8s.io/pod-lister created
clusterrolebinding.rbac.authorization.k8s.io/metallb-system:controller created
clusterrolebinding.rbac.authorization.k8s.io/metallb-system:speaker created
secret/webhook-server-cert created
service/webhook-service created
deployment.apps/controller created
daemonset.apps/speaker created
validatingwebhookconfiguration.admissionregistration.k8s.io/metallb-webhook-configuration created
root@k8smaster01:~#

Next create IPAddressPool resource. For IP addresses choose and assign the unassigned IP address range in the yaml file configuration. In my LAB environment I am using 192.168.34.0/24 IP address block. From this block I will carve out and use the 192.168.34.230 to 192.168.34.240 IP range and will make sure it will not get used or assigned to other systems in my network. Apply the configuration.

root@k8smaster01:~# cat ippool.yaml
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: metallb
  namespace: metallb-system
spec:
  addresses:
  - 192.168.34.230-192.168.34.240
root@k8smaster01:~#
root@k8smaster01:~# kubectl apply -f ippool.yaml
ipaddresspool.metallb.io/metallb created
root@k8smaster01:~#

Next use the IP address pool name in L2Advertisement resource yaml file to advertise IP address in network infrastructure. Apply this yaml file configuration and create resource with kubectl tool

Below is the Kubernetes cluster configuration setup in my lab: 
Configure Nginx Load Balancer for the Kubernetes API Server - Part 1
Install and configure Kubernetes cluster master nodes using kubeadm - Part 2
Install and configure Kubernetes cluster worker nodes using kubeadm - Part 3

root@k8smaster01:~# cat lbl2adv.yaml
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  name: l2lbadv
  namespace: metallb-system
spec:
  ipAddressPools:
  - metallb
root@k8smaster01:~#
root@k8smaster01:~# kubectl apply -f lbl2adv.yaml
l2advertisement.metallb.io/l2lbadv created
root@k8smaster01:~#

MetalLB Load Balancer is ready in my bare metal Kubernetes cluster environment. Its time to test it. I will deploy few resources such as Namespace, Deployment (Nginx Image with custom static web pages) and Service with LoadBalancer type pointing to deployment. 

Download this project deployment yaml here or it is also available on github.com/janviudapi.

root@k8smaster01:~# kubectl apply -f lbtest.yaml
namespace/green-project created
deployment.apps/green created
service/green-svc created
root@k8smaster01:~#

#lbtest.yaml with Kubernetes resources #Namespace, Deployment and Services
#This will create a new Namespace, Deployment and lb Service will be created under this
apiVersion: v1
kind: Namespace
metadata:
  name: green-project
  labels:
    app: green
---
#This will create Deployment with 2 pod replicas of NGINX images - Labels: Green
apiVersion: apps/v1
kind: Deployment
metadata:
  name: green
  labels:
    app: green
  namespace: green-project
spec:
  replicas: 2
  selector:
    matchLabels:
      app: green
  template:
    metadata:
      labels:
        app: green
    spec:
      volumes:
      - name: websitedata
        emptyDir: {}
      initContainers:
      - name: webcontent
        image: busybox
        volumeMounts:
        - name: websitedata
          mountPath: /websitedata
        command: ["/bin/sh"]
        args: ["-c", 'echo "Welcome to http://vcloud-lab.com Green_Application" > /websitedata/index.html']
      containers:
      - name: green
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - name: websitedata
          mountPath: "/usr/share/nginx/html" #For nginx image path - "/usr/share/nginx/html"
          readOnly: true
---
#This will create a service with LoadBalancer type with label selector green
apiVersion: v1
kind: Service
metadata:
  name: green-svc
  namespace: green-project
spec:
  selector:
    app: green
  type: LoadBalancer
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

Once you get the information for services using kubectl tool, you can see there is an External-IP assigned to the service and TYPE is LoadBalancer. In absence of LoadBalancer such as MetalLB for Bare Metal, you will see External-IP is pending or none. LoadBalancer assigns the first IP address from the address pool as mentioned above.

root@k8smaster01:~#
root@k8smaster01:~# kubectl get all -n green-project
NAME                         READY   STATUS    RESTARTS   AGE
pod/green-7dd977478c-nrcbp   1/1     Running   0          89s
pod/green-7dd977478c-xpvtz   1/1     Running   0          89s

NAME                TYPE           CLUSTER-IP       EXTERNAL-IP      PORT(S)        AGE
service/green-svc   LoadBalancer   10.110.135.177   192.168.34.230   80:32193/TCP   89s

NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/green   2/2     2            2           89s

NAME                               DESIRED   CURRENT   READY   AGE
replicaset.apps/green-7dd977478c   2         2         2       89s
root@k8smaster01:~#

Test the External-IP in the browser from any other system. You will get the response and Load Balancer is working good.

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