Go for DevOps/

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Deploying a Load-Balanced HTTP Application Using Go

Deploying a Load-Balanced HTTP Application Using Go

Understand how to handle the NGINX deployment of a load-balanced HTTP application with Go.

We'll cover the following...

Now that we understand a bit more about the Kubernetes API and the resources exposed by the API, we can move away from kubectl toward using Go.

In this lesson, we will use Go to do many of the same things we did in the previous section using kubectl. We will authenticate using our default context and create a namespace. However, we will not stop there. We will deploy a load-balanced HTTP application to our cluster and watch the logs stream to STDOUT as we make requests to the service.

Click the “Run” button below to start this demo:

module github.com/Go-for-DevOps/chapter/14/workloads

go 1.17

require (
	github.com/Azure/go-autorest/autorest/to v0.4.0
	k8s.io/api v0.23.4
	k8s.io/apimachinery v0.23.4
	k8s.io/client-go v0.23.4
)

require (
	github.com/Azure/go-autorest v14.2.0+incompatible // indirect
	github.com/davecgh/go-spew v1.1.1 // indirect
	github.com/go-logr/logr v1.2.0 // indirect
	github.com/gogo/protobuf v1.3.2 // indirect
	github.com/golang/protobuf v1.5.2 // indirect
	github.com/google/go-cmp v0.5.5 // indirect
	github.com/google/gofuzz v1.1.0 // indirect
	github.com/googleapis/gnostic v0.5.5 // indirect
	github.com/imdario/mergo v0.3.5 // indirect
	github.com/json-iterator/go v1.1.12 // indirect
	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
	github.com/modern-go/reflect2 v1.0.2 // indirect
	github.com/spf13/pflag v1.0.5 // indirect
	golang.org/x/net v0.0.0-20211209124913-491a49abca63 // indirect
	golang.org/x/oauth2 v0.0.0-20210819190943-2bc19b11175f // indirect
	golang.org/x/sys v0.0.0-20210831042530-f4d43177bf5e // indirect
	golang.org/x/term v0.0.0-20210615171337-6886f2dfbf5b // indirect
	golang.org/x/text v0.3.7 // indirect
	golang.org/x/time v0.0.0-20210723032227-1f47c861a9ac // indirect
	google.golang.org/appengine v1.6.7 // indirect
	google.golang.org/protobuf v1.27.1 // indirect
	gopkg.in/inf.v0 v0.9.1 // indirect
	gopkg.in/yaml.v2 v2.4.0 // indirect
	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
	k8s.io/klog/v2 v2.30.0 // indirect
	k8s.io/kube-openapi v0.0.0-20211115234752-e816edb12b65 // indirect
	k8s.io/utils v0.0.0-20211116205334-6203023598ed // indirect
	sigs.k8s.io/json v0.0.0-20211020170558-c049b76a60c6 // indirect
	sigs.k8s.io/structured-merge-diff/v4 v4.2.1 // indirect
	sigs.k8s.io/yaml v1.2.0 // indirect
)
The workloads demo

Enter these commands in the terminal above:

Press + to interact
kind create cluster --name workloads --config kind-config.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/main/deploy/static/provider/kind/deploy.yaml
kubectl wait --namespace ingress-nginx \
  --for=condition=ready pod \
  --selector=app.kubernetes.io/component=controller \
  --timeout=90s

Wait a few moments for the last command to finish running. Then, continue with these commands:

Press + to interact
cd /usercode/Go-for-DevOps/chapter/14/workloads/
go run .

The preceding commands will create a KinD cluster named workloads and use a config file that will enable host network ingress for the cluster. We will use ingress to expose the service running in the cluster. The command then deploys the NGINX ingress controller and waits for it to be ready. Finally, we run our Go program to deploy our application. After the service has been deployed and is running, open a browser with the URL beneath the Run button. We should see the following when we browse there:

The deployed NGINX hello world
The deployed NGINX hello world

We should see the request logs stream to STDOUT. They should look like the following:

10.244.0.7 - - [07/Mar/2022:02:34:59 +0000] "GET /hello HTTP/1.1" 200 7252 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.3 Safari/605.1.15" "172.22.0.1"

If we refresh the page, we should see the server name change, indicating that the requests are load-balancing across the two pod replicas in the deployment. Press “Ctrl + C” to terminate the Go program.

To tear down the cluster, run the following command:

Press + to interact
kind delete cluster --name workloads

The preceding command will delete the kind cluster named workloads. Next, let's explore this Go application to understand what just happened.

The code

Let's dive right into the code and see what is happening in this Go ...