Microservices architecture is the way to go when you want to release new features multiple times per day, but most of the time, microservices need to connect to each other. This is when Kubernetes comes in to orchestrate the life and networking of Dockerized microservices, and on top of that, it is reliable and performs very well. However, when developers want to debug or test a small change in a service that depends on other services located in a remote Kubernetes cluster, dev cycles can become a lot slower. A developer needs to do the following to see the changes:

1. Write code locally,
2. Create a container image and then push it to the container register,
3. Apply the Kubernetes configuration with the updated container image.

Fortunately, there is an open-source tool called Telepresence which helps developers in this matter. Telepresence creates a fake deployment, starts a proxy inside your Kubernetes cluster, and forwards all your requests from the cluster to your local process. The following example shows how to use this excellent tool.

Requirements

• Kuberntes cluster (GCP, Minikube, AWS...)
• Kubectl
• Docker
• Install Telepresence

To install Telepresence on Ubuntu 18, run:

curl -s https://packagecloud.io/install/repositories/datawireio/telepresence/script.deb.sh | sudo bash
sudo apt install --no-install-recommends telepresence

For other OS, go to the official Telepresence documentation.

Getting Started

Two applications will be running, the Golang one inside the Kubernetes cluster and the Spring Boot one on your local machine using Telepresence. There will be communication in both directions, so the remote service will be able to call the Java application and vice versa.

Remote Service

main.go

package main

import (
  "io/ioutil"
  "log"
  "net/http"

  "github.com/gin-gonic/gin"
)

func main() {
  router := SetupRouter()
  router.Run(":8081")
}

func SetupRouter() *gin.Engine {
  r := gin.Default()

  r.GET("/golang", func(c *gin.Context) {
  c.String(200, "Hello from Golang Service")
  })

  r.GET("/java", func(c *gin.Context) {
    resp, err := http.Get("http://java-telepresence-service:8080/java")
    if err !=nil {
    log.Fatal(err)
    }
    defer resp.Body.Close()
    contents, err := ioutil.ReadAll(resp.Body)
    c.String(200, string(contents))
  })

  return r
}

Dockerfile

FROM golang:latest 
WORKDIR /go/src/golang-telepresence-service
RUN go get -d -v github.com/gin-gonic/gin
COPY main.go .
RUN CGO_ENABLED=0 GOOS=linux go build -a -o main .

FROM alpine:latest
RUN apk --no-cache add ca-certificates
WORKDIR /root/
COPY --from=0 /go/src/golang-telepresence-service/main .
CMD ["./main"]

deployment.yaml

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: golang-telepresence-service
spec:
  replicas: 1
  template:
    metadata: {labels: {app: golang-telepresence-service}}
    spec:
      containers:
      - name: golang-telepresence-service
        image: smartinrub/golang-telepresence-service
        imagePullPolicy: Always
        command:
        ports:
          - containerPort: 8081

service.yaml

kind: Service
apiVersion: v1
metadata:
  name: golang-telepresence-service
spec:
  type: LoadBalancer
  selector:
    app: golang-telepresence-service
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8081

Now you are ready to build and push the image to your repository and apply the Kubernetes specifications:

docker build -t smartinrub/golang-telepresence-service .
docker push smartinrub/golang-telepresence-service
kubectl apply --filename deployment.yaml
kubectl apply --filename service.yaml

The source code can be found here.

Local Service

The Spring Boot application will be like so:

@RestController
publicclassMainController{

  private RestTemplate restTemplate = new RestTemplate();

  @GetMapping("/java")
  public String hello(){
  return"Hello from Java Service";
  }

  @GetMapping("/golang")
  public String callGoService(){
  return restTemplate.getForObject("http://golang-telepresence-service/golang", String.class);
  }
}

The source code can be found here.

Telepresence

telepresence --new-deployment java-telepresence-service --expose 8080

The previous command will create a deployment in your Kubernetes cluster and will forward all the calls to your local port 8080. Make sure to use the correct name for the service, since it will be used by the Kubernetes DNS server.

The Go application will be listening on port 80 from outside the pod, so the call to the service will be:

curl -X GET http://golang-telepresence-service/java

The Java application will be listening on port 8080, and will be able to be reached by hitting

curl -X http://java-telepresence-service:8080/golang

As you can see, from your local machine you can call the Java service which will hit the remote Kubernetes remote service and vice versa.

Conclusion

With Telepresence, testing or debugging features of a service, which depends on other services, is not a problem anymore. You can make as many changes as you want on your local application and test them out against a remote service without having to do a whole deployment process on Kubernetes.