Deploying a Golang web apps to Heroku

l-lin included in post

2015-01-31 563 words 3 minutes

Deploying a Golang web apps to Heroku is quite easy.

Heroku configuration

Heroku configurations are fetched from the OS environment variables.

So to fetch the webapp port, you will need to call os.Getenv("PORT").

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package main

import (
    "net/http"
	"os"
	"log"
	"fmt"
)

func main() {
	port := GetPort()
	log.Println("[-] Listening on...", port)
    http.HandleFunc("/", func (res http.ResponseWriter, req *http.Request) {
        fmt.Fprintln(res, "hello, world")
    })

    err := http.ListenAndServe(":"+os.Getenv("PORT"), nil)
    if err != nil {
      panic(err)
    }
}

func GetPort() string {
	port := os.Getenv("PORT")
	if port == "" {
		port = "4747"
		log.Println("[-] No PORT environment variable detected. Setting to ", port)
	}
	return ":" + port
}

That’s everything you need to do in your Golang webapp.

Now, you will need to tell Heroku to add the following buildpack to your webapps:

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cd /path/to/golang/app
heroku create example -b https://github.com/kr/heroku-buildpack-go.git

Before pushing to Heroku, you will need to save your app dependencies. Heroku support Godep for dependency management. First install Godep:

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go get -u github.com/tools/godep

Save your dependencies:

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godep save
git add -A
git commit -m "Add Godep"

Now, you are good to go!

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git push heroku master

Adding a Database to your Web app

Heroku has made the life of developper easier. To add a new database to your webapp, it’s really easy. For example, I needed to add a Postgresql. I just needed to execute one command line and the configuration is fetched from the environment variables:

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heroku addons:add heroku-postgresql:dev

More information on Heroku’s documentation.

Now to connect to the database, you will need:

to get the Postgresql driver
fetch Heroku’s DB configuration from the DATABASE_URL environment variable

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package main

import (
	_ "github.com/lib/pq"
	"log"
    "database/sql"
	"os"
)

// Fetch the list of novels
func GetList() []*Novel {
	novels := make([]*Novel, 0)
	database := connect()
	defer database.Close()

	rows, err := database.Query("SELECT id, title, url, image_url, summary, favorite FROM novels")
	if err != nil {
		log.Fatalf("[x] Error when getting the list of novels. Reason: %s", err.Error())
	}
	for rows.Next() {
		n := toNovel(rows)
		if n.IsValid() {
			novels = append(novels, n)
		}
	}
	if err := rows.Err(); err != nil {
		log.Fatalf("[x] Error when getting the list of novels. Reason: %s", err.Error())
	}
	return novels
}

// Connect to Heroku database using the OS env DATABASE_URL
func connect() *sql.DB {
	dbUrl := os.Getenv("DATABASE_URL")
	database, err := sql.Open("postgres", dbUrl)
	if err != nil {
		log.Fatalf("[x] Could not open the connection to the database. Reason: %s", err.Error())
	}
	return database
}

// Fetch the content of the rows and build a new novel
func toNovel(rows db.RowMapper) *Novel {
	var id string
	var title string
	var url string
	var imageUrl string
	var summary string
	var favorite bool

	rows.Scan(&id, &title, &url, &imageUrl, &summary, &favorite)

	return &Novel{
		Id: id,
		Title: title,
		Url: url,
		ImageUrl: imageUrl,
		Summary: summary,
		Favorite: favorite,
	}
}