Golang + CircleCI + Heroku

Simple Golang string flip code called by a webpage deployed in Heroku by CircleCI.

Here is the live deployment in Heroku: https://go-circle.herokuapp.com/

1. Requirements

• GitHub account (https://github.com), so you can build your app in CircleCI servers.
• Heroku Account https://www.heroku.com, to deploy the webpage in Heroku servers.
• CircleCI connection (https://circleci.com), provide CircleCI access to your repository in GitHub.

2. Knowing the source code

This repo contains the following source files:

• strings.go: a very small golang code to flip a given string
• strings_test.go: unit test cases in golang for CircleCI to run

// flip reverses all the characters on the give string s
func Flip(s string) string {
	if len(s) <= 1 {
		return s
	}
	return s[len(s)-1:] + Flip(s[:len(s)-1])
}

• main.go: main class with the endpoints and the setters for the html template

  # the endpoints available 
  http.HandleFunc("/time", func(w http.ResponseWriter, r *http.Request) {
		...
	})

	http.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {
		...
	})

	http.HandleFunc("/flip", func(w http.ResponseWriter, r *http.Request) {
		...
	})

• temp.html: the actual webpage that we are going to visualize

# loading the info as a parameter from the golang code
<div class="content">
	Current IP: {{.ServerIP}}<br>
	Deployed: {{.Deployed}}<br>
	Version: {{.Version}}
</div>
...
# calling flip's endpoint 
<script>
    function flipFunc() {
		var callTo = "http://{{.ServerIP}}:{{.Port}}/flip?text=" + toflip.value;
		var xhttp = new XMLHttpRequest();
	    xhttp.onreadystatechange = function() {
	         if (this.readyState == 4 && this.status == 200) {
				document.getElementById('fliResult').innerHTML = this.responseText;
	         }
	    };
	    xhttp.open("GET", callTo, true);
	   	xhttp.setRequestHeader("Content-type", "text/plain");
	    xhttp.send();
 }
</script>

Heroku requiered files: This two files work as a descriptors to deploy Golang apps into Heroku servers

• requirements.txt: that at ths point are none, so its a blank file
• Godeps/Godeps.json: the descriptor of the Go Version to use

{
	"ImportPath": "github.com/freeformz/go-heroku-example",
	"GoVersion": "go1.4.2",
  ...
}

CircleCI config.yml: This file setup the actual building job in Circle and the futher deployment in Heroku.

# Here the orb for Heroku connection
orbs:
  heroku: circleci/[email protected]
  ...
    # Calling remotly the github repo
    working_directory: /go/src/github.com/twogg-git/go-circleci
    steps:
      - checkout
      - run: go get -v -t -d ./...
      - run: go test -v ./...
  ...
        # And deploying in Heroku
        - run:
            name: Deploy Master to Heroku
            command: |
              git push https://heroku:$HEROKU_KEY@git.heroku.com/go-circle.git master
 ...

Dockerfile: This part is more like a bonus, because we are using Heroku to deploy online the webpage.

  FROM golang:1.10-alpine3.7 as builder
  WORKDIR /go/src/go-circleci/main
  COPY . .
  RUN go get -d ./... && go build -o main .

  FROM alpine:3.8
  RUN apk --no-cache add ca-certificates
  WORKDIR /root/
  COPY --from=builder /go/src/go-circleci/main .

  EXPOSE 8080
  ENTRYPOINT ./main

3. Creating your golang repo

4. Setting up Heroku

Heroku's dinamic port in the code

Heroku dynamically assigns your app a port, so you can't set the port to a fixed number. Heroku adds the port to the env, so you can pull it from there. Heroku configurations are fetched from the OS environment variables. So to fetch the webapp port, you will need to call os.Getenv("PORT").

func getPort() string {
	port := os.Getenv("PORT")
	if port == "" {
		port = PORT
		log.Println("[-] No PORT environment variable detected. Setting to ", port)
	}
	return port
}

Source: https://l-lin.github.io/post/2015/2015-01-31-golang-deploy_to_heroku/

Getting the HEROKU_KEY

https://devcenter.heroku.com/articles/go-support#go-versions https://medium.com/forloop/continuously-deploy-your-golang-binaries-using-circleci-and-heroku-docker-eb27e06d68f2 https://circleci.com/docs/2.0/deployment-integrations/#heroku

To get your HEROKU_KEY go to https://dashboard.heroku.com/account then API Key.

        # And deploying in Heroku
        - run:
            name: Deploy Master to Heroku
            command: |
              git push https://heroku:$HEROKU_KEY@git.heroku.com/go-circle.git master
 ...

5. Setting up CircleCI

BONUS: Docker deployment

Local Docker Deployment

To run the container. Public docker registry: https://hub.docker.com/r/twogghub/go-circle

docker run --name go-circle -p 8181:8080 -t twogghub/go-circle:v1

Then test the webpage in your browser: http:localhost:8181

Local building and deployment

To build locally the image, go to the folder's project then run:

docker build -t go-circle .
docker run --name go-circle -p 8181:8080 -t go-circle