Link Docker container example between golang1.3.3-onbuild and postgres:9.3.5 with Docker v1.2.0

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README.md

README.md

Link Docker container example

This example illustrates how to link Docker containers with following images. Docker version is 1.2.0.

• golang1.3.3-onbuild
• postgres:9.3.5

How to start

If you are on Mac OSX, follows the next Boot2Docker section.

Boot2Docker

As described on here, you should configure your network before you start a boot2docker VM.

$ boot2docker init
$ ./for-boot2docker.sh
$ boot2docker up

Run Postgres

You can pull official postgres and run it simply.

$ docker run --name some-postgres -d postgres:9.3.5

You'll be able to see postgres with docker ps.

Run the sample Go app

At first, you need to build the app to an image.

$ docker build --tag="test:1.0" .

Since you started a postgres container, you can link that with --link flag.

$ docker run -p 49153:8080 --name some-app --link some-postgres:postgres -d test:1.0

The docker ps will show something similar to below.

$ docker ps
CONTAINER ID        IMAGE               COMMAND                CREATED             STATUS              PORTS                     NAMES
f87470a6c176        test:1.0            "go-wrapper run"       22 minutes ago      Up 22 minutes       0.0.0.0:49153->8080/tcp   some-app
32cc507dce51        postgres:9.3.5      "/docker-entrypoint.   26 minutes ago      Up 26 minutes       5432/tcp                  some-app/postgres,some-postgres

You can see the app with curl.

$ curl http://localhost:49153/

Or if you are using boot2docker with Mac OSX, You need to know to IP address that boot2docker VM is on.

$ boot2docker ip # it'll show ip address
$ # assume the IP address is 192.168.59.103
$ curl http://192.168.59.103:49153/

Dockerfile

FROM golang:1.3.3-onbuild
EXPOSE 8080

foo.go

package main

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

var (
	db *sql.DB
	id = 1
)

func handler(w http.ResponseWriter, r *http.Request) {
	var count int
	err := db.QueryRow(`
		SELECT num
		FROM count
		WHERE id = $1
	`, id).Scan(&count)
	if err != nil {
		log.Fatal(err)
	}
	count += 1
	fmt.Fprintf(w, "Count is %d", count)
	_, err = db.Exec(`
		UPDATE count
		SET (num) = ($2)
		WHERE id = $1
	`, id, count)
	if err != nil {
		log.Fatal(err)
	}
}

func main() {
	addr := os.Getenv("POSTGRES_PORT_5432_TCP_ADDR")
	port := os.Getenv("POSTGRES_PORT_5432_TCP_PORT")
	log.Println(addr, port)
	var err error
	db, err = sql.Open("postgres", fmt.Sprintf("port=%s host=%s user=postgres sslmode=disable", port, addr))
	if err != nil {
		log.Fatal(err)
	}
	_, err = db.Exec(`
		DROP TABLE IF EXISTS count;
		CREATE TABLE count (
			id integer PRIMARY KEY,
			num integer NOT NULL
		);
		INSERT INTO count (id, num) VALUES (1, 0)
	`)
	if err != nil {
		log.Fatal(err)
	}
	http.HandleFunc("/", handler)
	http.ListenAndServe(":8080", nil)
}

for-boot2docker.sh

for i in {49153..49154}; do
 VBoxManage modifyvm "boot2docker-vm" --natpf1 "tcp-port$i,tcp,,$i,,$i";
 VBoxManage modifyvm "boot2docker-vm" --natpf1 "udp-port$i,udp,,$i,,$i";
done