To implement a load balancer and horizontal pod auto-scaler for the deployed image.
- Go to settings → Kubernetes
- Check the option 'Enable Kubernetes'
- Click 'Apply & Restart'
Pods are configured in the yaml file. The image used is nginx. Create Deployment by running the following command:
$ kubectl apply -f ./run-my-nginx.yaml
deployment.apps/my-nginx created
After a few moments, the Deployments should be ready. You can check running Deployments by executing the command:
$ kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
my-nginx 2/2 2 2 23m
In this Deployment, we have specified 2 replicas in run-my-nginx.yaml. You can check running Pods too by running:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
my-nginx-5b56ccd65f-4sv4j 1/1 Running 0 9m26s
my-nginx-5b56ccd65f-nhrvb 1/1 Running 0 9m26s
This is to create a Service for my-nginx Deployment.
$ kubectl expose deployment my-nginx
service/my-nginx exposed
$ kubectl get service
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 5d19h
my-nginx ClusterIP 10.96.195.245 <none> 80/TCP 4s
Following this link: https://kubernetes.github.io/ingress-nginx/deploy/
First, we need to install NGINX Ingress Controller for Ingress to work. Before running the following installation command, make sure Kubernetes is enabled at Docker settings.
$ kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.0.4/deploy/static/provider/cloud/deploy.yaml
namespace/ingress-nginx created
serviceaccount/ingress-nginx created
configmap/ingress-nginx-controller created
clusterrole.rbac.authorization.k8s.io/ingress-nginx created
clusterrolebinding.rbac.authorization.k8s.io/ingress-nginx created
role.rbac.authorization.k8s.io/ingress-nginx created
rolebinding.rbac.authorization.k8s.io/ingress-nginx created
service/ingress-nginx-controller-admission created
service/ingress-nginx-controller created
deployment.apps/ingress-nginx-controller created
ingressclass.networking.k8s.io/nginx created
validatingwebhookconfiguration.admissionregistration.k8s.io/ingress-nginx-admission created
serviceaccount/ingress-nginx-admission created
clusterrole.rbac.authorization.k8s.io/ingress-nginx-admission created
clusterrolebinding.rbac.authorization.k8s.io/ingress-nginx-admission created
role.rbac.authorization.k8s.io/ingress-nginx-admission created
rolebinding.rbac.authorization.k8s.io/ingress-nginx-admission created
job.batch/ingress-nginx-admission-create created
job.batch/ingress-nginx-admission-patch created
A few pods should start at ingress-nginx namespace.
$ kubectl get pods --namespace=ingress-nginx
NAME READY STATUS RESTARTS AGE
ingress-nginx-admission-create-7mhhk 0/1 Completed 0 54s
ingress-nginx-admission-patch-k9zjw 0/1 Completed 1 54s
ingress-nginx-controller-5c8d66c76d-6zb2h 1/1 Running 0 54s
With Ingress Controller set up, we can now apply the Ingress resource.
Following: https://kubernetes.github.io/ingress-nginx/deploy/
ingress-nginx.yaml file is configured with ingress rules and sticky session, where the backend Service is my-nginx created previously. Run the following command to apply the Ingress:
$ kubectl apply -f ./ingress-nginx.yaml
ingress.networking.k8s.io/ingress-nginx created
$ kubectl get ingress
NAME CLASS HOSTS ADDRESS PORTS AGE
ingress-nginx nginx demo.localdev.me 80 3s
Next, forward the local port to the Ingress controller. This needs to be done for local testing, as demo.localdev.me is not a deployed endpoint.
$ kubectl port-forward --namespace=ingress-nginx service/ingress-nginx-controller 8080:80
Forwarding from 127.0.0.1:8080 -> 80
Forwarding from [::1]:8080 -> 80
Side note: You can restart the whole process with
$ kubectl delete namespace ingress-nginx
To test out sticky sessions, keep the above terminal running and test it out in browser.
- Access
http://demo.localdev.me:8080/and check for cookies.INGRESS_COOKIEwill be set and it will not change after refreshing the page.
- Test it out in another browser to see a different cookie value, which also does not change after refreshing the page.
In order for the Ingress resource to work, the cluster must have an ingress controller running.
Ingress should be the rules for the traffic, which indicate the destination of a request will go through in the cluster. Ingress Controller is the implementation for the Ingress.
Define a horizontal pod autoscaler as such:
$ kubectl autoscale deployment my-nginx --cpu-percent=50 --min=1 --max=10
horizontalpodautoscaler.autoscaling/my-nginx autoscaled
Check the initial state of HPA:
$ kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
my-nginx Deployment/my-nginx 0%/50% 1 10 2 3m
Check the initial state of pods:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
my-nginx-5cfd745b65-dl5ts 1/1 Running 0 3m
my-nginx-5cfd745b65-mldw5 1/1 Running 0 3m
Run the python script to increase the load. The python scripts creates an infinite loop of GET request. Remember to keep the kubectl port-forward process running.
$ python request.py
Check the state of HPA with python script running. Notice that the number of replicas increases to handle the increased load.
$ kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
my-nginx Deployment/my-nginx 212%/50% 1 10 8 17m
Check the running pods:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
my-nginx-5cfd745b65-56d9j 1/1 Running 0 2m57s
my-nginx-5cfd745b65-8hqfs 1/1 Running 0 57s
my-nginx-5cfd745b65-dl5ts 1/1 Running 0 19m
my-nginx-5cfd745b65-f7r8q 1/1 Running 0 57s
my-nginx-5cfd745b65-fk2c2 1/1 Running 0 2m57s
my-nginx-5cfd745b65-fqnwl 1/1 Running 0 117s
my-nginx-5cfd745b65-j4l6h 1/1 Running 0 117s
my-nginx-5cfd745b65-k6t6b 1/1 Running 0 117s
my-nginx-5cfd745b65-mldw5 1/1 Running 0 7m33s
my-nginx-5cfd745b65-xptd8 1/1 Running 0 117s
Stop the load and HPA metrics should be uploaded in a few moment. The redundant replicas takes a while to terminate.
$ kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
my-nginx Deployment/my-nginx 0%/50% 1 10 10 37m
You should see the pods terminating after a while. Please be patient because it takes a while.
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
my-nginx-5cfd745b65-5cgcs 0/1 Terminating 0 7m12s
my-nginx-5cfd745b65-clnsz 0/1 Terminating 0 6m12s
my-nginx-5cfd745b65-dl5ts 1/1 Running 0 9m4s
my-nginx-5cfd745b65-fj7wr 1/1 Running 0 7m12s
my-nginx-5cfd745b65-jd6xt 0/1 Terminating 0 6m12s
my-nginx-5cfd745b65-nrgdz 0/1 Terminating 0 6m12s
my-nginx-5cfd745b65-s9tcw 1/1 Running 0 8m50s
my-nginx-5cfd745b65-wk87g 0/1 Terminating 0 5m12s
my-nginx-5cfd745b65-z8jjs 0/1 Terminating 0 6m12s
You can also check the history of how HPA autoscales by running:
$ kubectl describe hpa my-nginx
Name: my-nginx
Namespace: default
Labels: <none>
Annotations: <none>
CreationTimestamp: Sat, 06 Nov 2021 16:58:30 +0800
Reference: Deployment/my-nginx
Metrics: ( current / target )
resource cpu on pods (as a percentage of request): 0% (0) / 50%
Min replicas: 1
Max replicas: 10
Deployment pods: 1 current / 1 desired
Conditions:
Type Status Reason Message
---- ------ ------ -------
AbleToScale True ReadyForNewScale recommended size matches current size
ScalingActive True ValidMetricFound the HPA was able to successfully calculate a replica count from cpu resource utilization (percentage of request)
ScalingLimited True TooFewReplicas the desired replica count is less than the minimum replica count
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning FailedGetResourceMetric 11m (x13 over 23m) horizontal-pod-autoscaler failed to get cpu utilization: missing request for cpu
Warning FailedComputeMetricsReplicas 11m (x13 over 23m) horizontal-pod-autoscaler invalid metrics (1 invalid out of 1), first error is: failed to get cpu utilization: missing request for cpu
Warning FailedGetResourceMetric 10m horizontal-pod-autoscaler failed to get cpu utilization: did not receive metrics for any ready pods
Normal SuccessfulRescale 8m4s horizontal-pod-autoscaler New size: 8; reason: cpu resource utilization (percentage of request) above target
Normal SuccessfulRescale 2m4s horizontal-pod-autoscaler New size: 3; reason: All metrics below target
- Ingress + Sticky session:
- HPA: https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale-walkthrough/
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